Add multi-process self-play, eval workers, MCTS Cython port

Key changes for ISMCTS speed and correctness:
- Cython port: HeuristicBot helpers (`heuristic_cy.pyx` + new `.pxd`) and
  ISMCTS searcher (`mcts.pyx`) now run as cdef. Both share a fast
  unified-action path through GameState's C interface to avoid Python
  round-trips on hot rollout/tree-walk paths.
- Multi-process self-play and eval: `workers.py`, `eval_worker.py`,
  `interleaved_self_play.py`, plus trainer wiring with ProcessPoolExecutor
  + spawn context. Eval inside `evaluate.py` is parallel per opponent.
- ISMCTS-specific eval (`evaluate.py`) runs MCTS at decision time so the
  metric matches deploy mode; `evaluation.eval_with_mcts` flag preserves
  backwards-compatible policy-only eval when needed.
- Trainer logs progress per phase (self-play start/done, eval per
  opponent), and value loss is now scaled by `value_scale` so policy and
  value losses sit on comparable magnitudes.
- Compact info-set key (`info_set.py`) using packed-struct format and
  child-key reuse during MCTS descent to cut per-step canonicalization.

Tests: 19 ISMCTS suite passing, including parity (Cython-vs-Python
sequential, batched-vs-sequential visit counts, push/pop round-trip).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

configs/ismcts/default.yaml

@@ -24,6 +24,8 @@ mcts:
   n_simulations: 50
   c_puct: 1.5
   max_depth: 200
+  parallel_simulations: 8
+  virtual_loss_value: 1.0
 temperature:
   training: 1.0
   eval: 0.0
@@ -32,6 +34,8 @@ training:
   gradient_steps_per_iter: 10
   batch_size: 128
   replay_capacity: 100000
+  interleave_games: 8
+  interleave_max_batch: 64
 optimization:
   learning_rate: 0.0003
   grad_clip: 5.0

configs/ismcts/mini.yaml

@@ -24,6 +24,8 @@ mcts:
   n_simulations: 50
   c_puct: 1.5
   max_depth: 100
+  parallel_simulations: 8
+  virtual_loss_value: 1.0
 temperature:
   training: 1.0
   eval: 0.0
@@ -32,6 +34,8 @@ training:
   gradient_steps_per_iter: 10
   batch_size: 128
   replay_capacity: 50000
+  interleave_games: 8
+  interleave_max_batch: 64
 optimization:
   learning_rate: 0.001
   grad_clip: 5.0

pyproject.toml

@@ -59,6 +59,14 @@ include = ["coolrl_lost_cities*"]
     "*.pxd",
     "*.pyx",
 ]
+"coolrl_lost_cities.games.classic.bots" = [
+    "*.pxd",
+    "*.pyx",
+]
+"coolrl_lost_cities.games.classic.ismcts" = [
+    "*.pxd",
+    "*.pyx",
+]
 
 [tool.ruff]
 line-length = 100

setup.py

@@ -30,6 +30,10 @@ extensions = cythonize(
             "coolrl_lost_cities.games.classic.bots.heuristic_cy",
             ["src/coolrl_lost_cities/games/classic/bots/heuristic_cy.pyx"],
         ),
+        Extension(
+            "coolrl_lost_cities.games.classic.ismcts.mcts",
+            ["src/coolrl_lost_cities/games/classic/ismcts/mcts.pyx"],
+        ),
     ],
     language_level=3,
     compiler_directives={

src/coolrl_lost_cities/games/classic/bots/heuristic_cy.pxd

@@ -0,0 +1,117 @@
+from ..game cimport GameState
+
+
+cdef class _CachedState:
+    cdef GameState _state
+    cdef public object config
+    cdef public object hands
+    cdef public object expeditions
+    cdef public object discards
+    cdef public object deck
+    cdef int hand_encoded[2][16]
+    cdef int hand_size[2]
+    cdef int expedition_top[2][8]
+    cdef int expedition_count[2][8]
+    cdef int expedition_handshakes[2][8]
+    cdef int expedition_numeric_sum[2][8]
+    cdef int expedition_last_numeric[2][8]
+    cdef int discard_top[8]
+    cdef int discard_count[8]
+    cdef int deck_remaining
+    cdef int total_scores[2]
+    cdef int current_player
+    cdef int phase
+    cdef int turn_count
+    cdef int n_colors
+    cdef int n_ranks
+    cdef int min_rank
+    cdef int hand_capacity
+    cdef int bonus_threshold
+    cdef int bonus_amount
+    cdef int expedition_penalty
+    cdef void _build(self, GameState state) except *
+    cpdef list legal_card_mask(self)
+    cpdef list legal_draw_mask(self)
+    cpdef bint can_play_card(self, int player, object card)
+    cpdef bint can_play_encoded(self, int player, int card)
+    cpdef bint has_numeric(self, int player, int color)
+    cpdef int score_diff(self, int player)
+
+
+cdef class HeuristicBot:
+    cdef public object params
+    cdef double color_commit_cache[2][8]
+    cdef unsigned char color_commit_valid[2][8]
+    cdef signed char playability_cache[2][8][17]
+    cdef void _reset_caches(self) noexcept
+    cpdef int act_cython(self, GameState state) except -1
+    cdef int _card_color_c(self, _CachedState state, int card) noexcept
+    cdef int _card_rank_c(self, _CachedState state, int card) noexcept
+    cdef int _num_c(self, _CachedState state, int card) noexcept
+    cdef int _play_action_c(self, int slot) noexcept
+    cdef int _discard_action_c(self, int slot) noexcept
+    cdef bint _legal_card_action_c(self, _CachedState state, int action) noexcept
+    cdef bint _legal_draw_action_c(self, _CachedState state, int action) noexcept
+    cdef bint _can_play_card_c(self, _CachedState state, int player, int card) noexcept
+    cdef bint _has_numeric_c(self, _CachedState state, int player, int color) noexcept
+    cdef int _opened_colors_c(self, _CachedState state, int player) noexcept
+    cdef int _first_legal_card_c(self, _CachedState state) noexcept
+    cdef int _first_legal_draw_c(self, _CachedState state) noexcept
+    cdef int _act_card_c(self, _CachedState state, object derived) except -1
+    cdef int _act_draw_c(self, _CachedState state, object derived) except -1
+    cdef int _best_handshake_play_c(
+        self, _CachedState state, int player, object derived, int deck_left
+    ) except -2
+    cdef int _best_number_play_c(
+        self, _CachedState state, int player, object derived, int deck_left
+    ) except -2
+    cdef double _started_expedition_play_value_c(
+        self, _CachedState state, int player, int card, object derived, int deck_left
+    ) except *
+    cdef bint _should_open_expedition_c(
+        self, _CachedState state, int player, int color, int opening_card, object derived, int deck_left
+    ) except *
+    cdef double _opening_plan_value_c(
+        self, _CachedState state, int player, int color, int opening_card, object derived, int deck_left
+    ) except *
+    cdef double _open_expedition_value_c(
+        self, _CachedState state, int player, int color, int opening_card, object derived, int deck_left
+    ) except *
+    cdef int _best_forced_open_c(
+        self, _CachedState state, int player, object derived, int deck_left
+    ) except -2
+    cdef int _best_discard_c(self, _CachedState state, int player, object derived) except -2
+    cdef double _visible_draw_value_c(
+        self, _CachedState state, int player, int card, object derived
+    ) except *
+    cdef double _visible_open_support_value_c(
+        self, _CachedState state, int player, int card, object derived
+    ) except *
+    cdef bint _visible_number_can_help_open_c(
+        self, _CachedState state, int player, int card, object derived
+    ) except *
+    cdef double _deck_draw_value_c(self, _CachedState state, object derived) except *
+    cdef double _card_value_for_me_c(
+        self, _CachedState state, int player, int card, object derived
+    ) except *
+    cdef double _card_value_for_opponent_c(
+        self, _CachedState state, int opponent, int card, object derived
+    ) except *
+    cdef double _color_commitment_c(
+        self, _CachedState state, int player, int color, object derived
+    ) except *
+    cdef double _public_color_commitment_for_opponent_c(
+        self, _CachedState state, int opponent, int color, object derived
+    ) except *
+    cdef double _bonus_potential_c(
+        self,
+        _CachedState state,
+        int player,
+        int color,
+        int extra_cards,
+        object derived,
+        int committed_cards,
+        int exclude_card,
+    ) except *
+    cdef double _new_color_open_penalty_c(self, int opened_colors) noexcept
+    cdef double _late_penalty_c(self, object derived, int deck_left) except *

src/coolrl_lost_cities/games/classic/bots/heuristic_cy.pyx

@@ -5,6 +5,10 @@ import logging
 from dataclasses import dataclass
 from functools import lru_cache
 
+from libc.string cimport memset
+
+from ..game cimport GameState as CGameState
+
 from ..game import Card, GameState, LostCitiesConfig
 from ..policy import LostCitiesPolicy, PolicyInput
 from .base import first_legal, legal_from_obs
@@ -18,6 +22,11 @@ except ImportError as exc:  # pragma: no cover
 PLAY_OR_DISCARD_ACTIONS_PER_SLOT = 2
 DRAW_FROM_DECK_ACTION = 0
 
+DEF MAX_HAND_SIZE = 16
+DEF MAX_COLORS = 8
+DEF MAX_RANKS = 16
+DEF MAX_ACTIONS = 64
+
 
 def play_action(slot: int) -> int:
     return PLAY_OR_DISCARD_ACTIONS_PER_SLOT * slot
@@ -34,35 +43,87 @@ def draw_from_discard_action(color: int) -> int:
 LOGGER = logging.getLogger("coolrl_lost_cities.games.classic.bots.heuristic")
 
 
-class _CachedState:
-    def __init__(self, state):
-        self._state = state
+cdef class _CachedState:
+    def __init__(self, CGameState state):
+        self._build(state)
         self.config = state.config
-        self.current_player = state.current_player
-        self.phase = state.phase
-        self.turn_count = state.turn_count
         self.hands = state.hands
         self.expeditions = state.expeditions
         self.discards = state.discards
         self.deck = state.deck
 
-    def legal_card_mask(self):
+    cdef void _build(self, CGameState state) except *:
+        cdef int player
+        cdef int slot
+        cdef int color
+        cdef int idx
+        cdef int length
+        if state.hand_size > MAX_HAND_SIZE:
+            raise ValueError("hand_size exceeds HeuristicBot fixed hand buffer")
+        if state.n_colors > MAX_COLORS:
+            raise ValueError("n_colors exceeds HeuristicBot fixed color buffer")
+        if state.n_ranks > MAX_RANKS:
+            raise ValueError("n_ranks exceeds HeuristicBot fixed rank buffer")
+        self._state = state
+        self.n_colors = state.n_colors
+        self.n_ranks = state.n_ranks
+        self.min_rank = state.min_rank
+        self.hand_capacity = state.hand_size
+        self.bonus_threshold = state.bonus_threshold
+        self.bonus_amount = state.bonus_amount
+        self.expedition_penalty = state.expedition_penalty
+        self.current_player = state.current_player
+        self.phase = state.phase_id
+        self.turn_count = state.turn_count
+        self.deck_remaining = state.deck_len
+        self.total_scores[0] = state.total_scores[0]
+        self.total_scores[1] = state.total_scores[1]
+        memset(&self.hand_encoded[0][0], 0, sizeof(self.hand_encoded))
+        memset(&self.expedition_top[0][0], 0, sizeof(self.expedition_top))
+        memset(&self.expedition_count[0][0], 0, sizeof(self.expedition_count))
+        memset(&self.expedition_handshakes[0][0], 0, sizeof(self.expedition_handshakes))
+        memset(&self.expedition_numeric_sum[0][0], 0, sizeof(self.expedition_numeric_sum))
+        memset(&self.expedition_last_numeric[0][0], 0, sizeof(self.expedition_last_numeric))
+        memset(&self.discard_top[0], 0, sizeof(self.discard_top))
+        memset(&self.discard_count[0], 0, sizeof(self.discard_count))
+        for player in range(2):
+            self.hand_size[player] = state.hand_lens[player]
+            for slot in range(state.hand_lens[player]):
+                self.hand_encoded[player][slot] = state.hand_cards[state._hand_index(player, slot)]
+            for color in range(state.n_colors):
+                idx = state._expedition_len_index(player, color)
+                length = state.expedition_lens[idx]
+                self.expedition_count[player][color] = length
+                self.expedition_handshakes[player][color] = state.handshake_counts[idx]
+                self.expedition_numeric_sum[player][color] = state.numeric_sums[idx]
+                self.expedition_last_numeric[player][color] = state.last_numeric_ranks[idx]
+                if length > 0:
+                    self.expedition_top[player][color] = state.expedition_cards[
+                        state._expedition_index(player, color, length - 1)
+                    ]
+        for color in range(state.n_colors):
+            length = state.discard_lens[color]
+            self.discard_count[color] = length
+            if length > 0:
+                self.discard_top[color] = state.discard_cards[state._discard_index(color, length - 1)]
+
+    cpdef list legal_card_mask(self):
         return self._state.legal_card_mask()
 
-    def legal_draw_mask(self):
+    cpdef list legal_draw_mask(self):
         return self._state.legal_draw_mask()
 
-    def can_play_card(self, player, card):
+    cpdef bint can_play_card(self, int player, object card):
         return self._state.can_play_card(player, card)
 
-    def has_numeric(self, player, color):
-        return self._state.has_numeric(player, color)
+    cpdef bint can_play_encoded(self, int player, int card):
+        return self._state._can_play_encoded_card_c(player, card)
 
-    def score_diff(self, player):
-        return self._state.score_diff(player)
+    cpdef bint has_numeric(self, int player, int color):
+        return self._state.last_numeric_rank(player, color) > 0
 
-    def __getattr__(self, name):
-        return getattr(self._state, name)
+    cpdef int score_diff(self, int player):
+        return self.total_scores[player] - self.total_scores[1 - player]
 
 
 @dataclass(frozen=True)
@@ -178,29 +239,756 @@ def derive_heuristic_config(
     )
 
 
-class HeuristicBot(LostCitiesPolicy):
+cdef class HeuristicBot:
     def __init__(self, params: HeuristicParams | None = None):
         self.params = params or HeuristicParams()
+        self._reset_caches()
+
+    cdef void _reset_caches(self) noexcept:
+        memset(&self.color_commit_cache[0][0], 0, sizeof(self.color_commit_cache))
+        memset(&self.color_commit_valid[0][0], 0, sizeof(self.color_commit_valid))
+        memset(&self.playability_cache[0][0][0], -1, sizeof(self.playability_cache))
+
+    cpdef int act_cython(self, CGameState state) except -1:
+        cdef _CachedState cstate = _CachedState(state)
+        cdef object derived
+        self._reset_caches()
+        derived = self._derived(state)
+        if cstate.phase == 0:
+            return self._act_card_c(cstate, derived)
+        return self._act_draw_c(cstate, derived)
 
     def act(self, obs_or_state: PolicyInput) -> int:
         if not isinstance(obs_or_state, GameState) and not hasattr(obs_or_state, "legal_mask"):
-            LOGGER.debug(
-                "HeuristicBot fallback to first legal: input_type=%s",
-                type(obs_or_state).__name__,
-            )
             return first_legal(legal_from_obs(obs_or_state))
 
-        LOGGER.debug(
-            "HeuristicBot heuristic path: player=%s phase=%s turn=%s",
-            obs_or_state.current_player,
-            obs_or_state.phase,
-            obs_or_state.turn_count,
-        )
-        state = _CachedState(obs_or_state)
-        if state.phase == "card":
-            return self._act_card(state)
+        if isinstance(obs_or_state, GameState):
+            return self.act_cython(obs_or_state)
 
-        return self._act_draw(state)
+        if obs_or_state.phase == "card":
+            return self._act_card(obs_or_state)
+
+        return self._act_draw(obs_or_state)
+
+    cdef inline int _card_color_c(self, _CachedState state, int card) noexcept:
+        return card // (state.n_ranks + 1)
+
+    cdef inline int _card_rank_c(self, _CachedState state, int card) noexcept:
+        return card % (state.n_ranks + 1)
+
+    cdef inline int _num_c(self, _CachedState state, int card) noexcept:
+        cdef int rank = self._card_rank_c(state, card)
+        if rank == 0:
+            return 0
+        return state.min_rank + rank - 1
+
+    cdef inline int _play_action_c(self, int slot) noexcept:
+        return 2 * slot
+
+    cdef inline int _discard_action_c(self, int slot) noexcept:
+        return 2 * slot + 1
+
+    cdef inline bint _legal_card_action_c(self, _CachedState state, int action) noexcept:
+        cdef int slot = action // 2
+        if action < 0 or action >= 2 * state.hand_capacity:
+            return False
+        if slot >= state.hand_size[state.current_player]:
+            return False
+        if action % 2 == 1:
+            return True
+        return self._can_play_card_c(
+            state,
+            state.current_player,
+            state.hand_encoded[state.current_player][slot],
+        )
+
+    cdef inline bint _legal_draw_action_c(self, _CachedState state, int action) noexcept:
+        cdef int color
+        if action == 0:
+            return state.deck_remaining > 0
+        color = action - 1
+        if color < 0 or color >= state.n_colors:
+            return False
+        return (
+            state.discard_count[color] > 0
+            and (state._state.pending_discarded_color < 0 or color != state._state.pending_discarded_color)
+        )
+
+    cdef bint _can_play_card_c(self, _CachedState state, int player, int card) noexcept:
+        cdef int color = self._card_color_c(state, card)
+        cdef int rank = self._card_rank_c(state, card)
+        cdef signed char cached
+        if color < 0 or color >= state.n_colors or rank < 0 or rank > state.n_ranks:
+            return False
+        cached = self.playability_cache[player][color][rank]
+        if cached >= 0:
+            return cached == 1
+        if rank == 0:
+            cached = 1 if state.expedition_last_numeric[player][color] == 0 else 0
+        else:
+            cached = 1 if rank > state.expedition_last_numeric[player][color] else 0
+        self.playability_cache[player][color][rank] = cached
+        return cached == 1
+
+    cdef bint _has_numeric_c(self, _CachedState state, int player, int color) noexcept:
+        return state.expedition_last_numeric[player][color] > 0
+
+    cdef int _opened_colors_c(self, _CachedState state, int player) noexcept:
+        cdef int color
+        cdef int count = 0
+        for color in range(state.n_colors):
+            if state.expedition_count[player][color] > 0:
+                count += 1
+        return count
+
+    cdef int _first_legal_card_c(self, _CachedState state) noexcept:
+        cdef int slot
+        cdef int card
+        cdef int player = state.current_player
+        for slot in range(state.hand_size[player]):
+            card = state.hand_encoded[player][slot]
+            if self._can_play_card_c(state, player, card):
+                return 2 * slot
+            return 2 * slot + 1
+        return 0
+
+    cdef int _first_legal_draw_c(self, _CachedState state) noexcept:
+        cdef int color
+        if self._legal_draw_action_c(state, 0):
+            return 0
+        for color in range(state.n_colors):
+            if self._legal_draw_action_c(state, 1 + color):
+                return 1 + color
+        return 0
+
+    cdef int _act_card_c(self, _CachedState state, object derived) except -1:
+        cdef int player = state.current_player
+        cdef int action
+        action = self._best_handshake_play_c(state, player, derived, state.deck_remaining)
+        if action >= 0:
+            return action
+        action = self._best_number_play_c(state, player, derived, state.deck_remaining)
+        if action >= 0:
+            return action
+        if self._opened_colors_c(state, player) == 0:
+            action = self._best_forced_open_c(state, player, derived, state.deck_remaining)
+            if action >= 0:
+                return action
+        action = self._best_discard_c(state, player, derived)
+        if action >= 0:
+            return action
+        return self._first_legal_card_c(state)
+
+    cdef int _act_draw_c(self, _CachedState state, object derived) except -1:
+        cdef int player = state.current_player
+        cdef int color
+        cdef int action
+        cdef int best_action = -1
+        cdef int best_tie = -1
+        cdef double value
+        cdef double best_value = -1.0e100
+        if self._legal_draw_action_c(state, 0):
+            best_action = 0
+            best_tie = 1
+            best_value = self._deck_draw_value_c(state, derived)
+        for color in range(state.n_colors):
+            action = 1 + color
+            if not self._legal_draw_action_c(state, action):
+                continue
+            value = self._visible_draw_value_c(state, player, state.discard_top[color], derived)
+            if (
+                value > best_value
+                or (
+                    value == best_value
+                    and (0 > best_tie or (best_tie == 0 and action > best_action))
+                )
+            ):
+                best_value = value
+                best_tie = 0
+                best_action = action
+        if best_action >= 0:
+            return best_action
+        return self._first_legal_draw_c(state)
+
+    cdef int _best_handshake_play_c(
+        self, _CachedState state, int player, object derived, int deck_left
+    ) except -2:
+        cdef int slot
+        cdef int other_slot
+        cdef int card
+        cdef int other
+        cdef int color
+        cdef int number_count
+        cdef int number_sum
+        cdef double value
+        cdef double best_value = -1.0e100
+        cdef int best_action = -1
+        if state._state.n_handshakes <= 0:
+            return -1
+        for slot in range(state.hand_size[player]):
+            card = state.hand_encoded[player][slot]
+            if not self._legal_card_action_c(state, 2 * slot) or self._card_rank_c(state, card) != 0:
+                continue
+            color = self._card_color_c(state, card)
+            if state.expedition_last_numeric[player][color] > 0:
+                continue
+            number_count = 0
+            number_sum = 0
+            for other_slot in range(state.hand_size[player]):
+                if other_slot == slot:
+                    continue
+                other = state.hand_encoded[player][other_slot]
+                if (
+                    self._card_color_c(state, other) == color
+                    and self._card_rank_c(state, other) != 0
+                    and self._can_play_card_c(state, player, other)
+                ):
+                    number_count += 1
+                    number_sum += self._num_c(state, other)
+            if number_count < derived.min_handshake_numeric_cards:
+                continue
+            if number_sum < derived.open_target_sum * self.params.handshake_target_multiplier:
+                continue
+            if deck_left <= derived.late_open_block_threshold:
+                continue
+            value = number_sum + 2.0 * number_count
+            value += self._bonus_potential_c(state, player, color, 0, derived, 1, card)
+            value -= self._late_penalty_c(derived, deck_left)
+            if value > best_value or (value == best_value and 2 * slot > best_action):
+                best_value = value
+                best_action = 2 * slot
+        return best_action
+
+    cdef int _best_number_play_c(
+        self, _CachedState state, int player, object derived, int deck_left
+    ) except -2:
+        cdef int slot
+        cdef int card
+        cdef int color
+        cdef double value
+        cdef double best_value = -1.0e100
+        cdef int best_action = -1
+        for slot in range(state.hand_size[player]):
+            card = state.hand_encoded[player][slot]
+            if not self._legal_card_action_c(state, 2 * slot) or self._card_rank_c(state, card) == 0:
+                continue
+            color = self._card_color_c(state, card)
+            if state.expedition_count[player][color] > 0:
+                value = self._started_expedition_play_value_c(
+                    state, player, card, derived, deck_left
+                )
+                if value > best_value or (value == best_value and 2 * slot > best_action):
+                    best_value = value
+                    best_action = 2 * slot
+                continue
+            if self._should_open_expedition_c(state, player, color, card, derived, deck_left):
+                value = self._open_expedition_value_c(state, player, color, card, derived, deck_left)
+                if value > best_value or (value == best_value and 2 * slot > best_action):
+                    best_value = value
+                    best_action = 2 * slot
+        return best_action
+
+    cdef double _started_expedition_play_value_c(
+        self, _CachedState state, int player, int card, object derived, int deck_left
+    ) except *:
+        cdef int color = self._card_color_c(state, card)
+        cdef int numeric_value = self._num_c(state, card)
+        cdef int slot
+        cdef int followup
+        cdef int projected_sum = state.expedition_numeric_sum[player][color] + numeric_value
+        cdef double value = 0.0
+        for slot in range(state.hand_size[player]):
+            followup = state.hand_encoded[player][slot]
+            if (
+                followup != card
+                and self._card_color_c(state, followup) == color
+                and self._card_rank_c(state, followup) != 0
+                and self._card_rank_c(state, followup) > self._card_rank_c(state, card)
+            ):
+                projected_sum += self._num_c(state, followup)
+        value += self.params.started_expedition_play_bonus
+        value += self.params.started_expedition_followup_bonus
+        value += <double>(state._state.min_rank + state._state.n_ranks - numeric_value)
+        if deck_left <= derived.late_deck_threshold:
+            value += 2.0 * numeric_value
+        elif deck_left <= derived.mid_deck_threshold:
+            value += 0.8 * numeric_value
+        if projected_sum < derived.open_target_sum:
+            value -= 6.0
+        value += 3.0 * state.expedition_handshakes[player][color]
+        value += self._bonus_potential_c(state, player, color, 0, derived, 1, card)
+        return value
+
+    cdef bint _should_open_expedition_c(
+        self, _CachedState state, int player, int color, int opening_card, object derived, int deck_left
+    ) except *:
+        if deck_left <= derived.late_open_block_threshold:
+            return False
+        return self._opening_plan_value_c(state, player, color, opening_card, derived, deck_left) > 0.0
+
+    cdef double _opening_plan_value_c(
+        self, _CachedState state, int player, int color, int opening_card, object derived, int deck_left
+    ) except *:
+        cdef int slot
+        cdef int card
+        cdef int rank
+        cdef int numbers = 0
+        cdef int handshakes = 0
+        cdef int number_sum = 0
+        cdef int high_count = 0
+        cdef int opened_colors = self._opened_colors_c(state, player)
+        cdef int opening_value = self._num_c(state, opening_card)
+        cdef double new_color_penalty = self._new_color_open_penalty_c(opened_colors)
+        cdef bint strong_open
+        cdef bint speculative_open
+        cdef bint single_late_open
+        cdef bint exceptional_open
+        for slot in range(state.hand_size[player]):
+            card = state.hand_encoded[player][slot]
+            if self._card_color_c(state, card) != color:
+                continue
+            rank = self._card_rank_c(state, card)
+            if rank == 0:
+                handshakes += 1
+            elif rank >= self._card_rank_c(state, opening_card):
+                numbers += 1
+                number_sum += self._num_c(state, card)
+                if rank >= derived.middle_rank:
+                    high_count += 1
+        strong_open = (
+            numbers >= derived.min_open_cards
+            and number_sum >= derived.open_target_sum
+            and (high_count > 0 or number_sum >= 0.85 * derived.max_color_sum)
+        )
+        speculative_open = (
+            opened_colors <= 2
+            and numbers >= 2
+            and number_sum >= 0.65 * derived.open_target_sum
+            and high_count > 0
+        )
+        single_late_open = (
+            deck_left <= derived.mid_deck_threshold and numbers >= 1 and opening_value >= 8
+        )
+        exceptional_open = (
+            numbers >= derived.min_open_cards + 1
+            and number_sum >= max(float(derived.break_even_sum), derived.open_target_sum * 1.4)
+            and high_count >= 2
+            and deck_left > derived.mid_deck_threshold
+        )
+        if opened_colors == 3:
+            speculative_open = False
+        if opened_colors >= 4:
+            strong_open = False
+            speculative_open = False
+            single_late_open = False
+        if strong_open:
+            return 6.0 + 0.25 * number_sum + 0.8 * numbers + 0.5 * handshakes - new_color_penalty
+        if speculative_open:
+            return 3.0 + 0.18 * number_sum + 0.7 * numbers + 0.4 * handshakes - new_color_penalty
+        if opened_colors == 3:
+            return 0.0
+        if exceptional_open:
+            return 10.0 + 0.3 * number_sum + 1.0 * numbers + 0.7 * high_count - new_color_penalty
+        if single_late_open:
+            return 1.5 + 0.2 * opening_value - new_color_penalty
+        return 0.0
+
+    cdef double _open_expedition_value_c(
+        self, _CachedState state, int player, int color, int opening_card, object derived, int deck_left
+    ) except *:
+        cdef int slot
+        cdef int card
+        cdef int rank
+        cdef int numbers = 0
+        cdef int handshakes = 0
+        cdef int number_sum = 0
+        cdef double value
+        for slot in range(state.hand_size[player]):
+            card = state.hand_encoded[player][slot]
+            if self._card_color_c(state, card) != color:
+                continue
+            rank = self._card_rank_c(state, card)
+            if rank == 0:
+                handshakes += 1
+            elif rank >= self._card_rank_c(state, opening_card):
+                numbers += 1
+                number_sum += self._num_c(state, card)
+        value = number_sum + 2.0 * numbers + 1.5 * handshakes
+        value += self._opening_plan_value_c(state, player, color, opening_card, derived, deck_left)
+        value += state.expedition_penalty
+        value += max(0.0, float(derived.middle_rank - self._card_rank_c(state, opening_card)))
+        value += self._bonus_potential_c(state, player, color, 0, derived, 1, opening_card)
+        value -= self._late_penalty_c(derived, deck_left)
+        return value
+
+    cdef int _best_forced_open_c(
+        self, _CachedState state, int player, object derived, int deck_left
+    ) except -2:
+        cdef int slot
+        cdef int card
+        cdef int color
+        cdef int other
+        cdef int number_count
+        cdef int number_sum
+        cdef double opening_value
+        cdef double forced_value
+        cdef double best_value = -1.0e100
+        cdef int best_action = -1
+        for slot in range(state.hand_size[player]):
+            card = state.hand_encoded[player][slot]
+            if not self._legal_card_action_c(state, 2 * slot) or self._card_rank_c(state, card) == 0:
+                continue
+            color = self._card_color_c(state, card)
+            if state.expedition_count[player][color] > 0:
+                continue
+            opening_value = self._opening_plan_value_c(state, player, color, card, derived, deck_left)
+            number_count = 0
+            number_sum = 0
+            for other_slot in range(state.hand_size[player]):
+                other = state.hand_encoded[player][other_slot]
+                if self._card_color_c(state, other) == color and self._card_rank_c(state, other) != 0:
+                    number_count += 1
+                    number_sum += self._num_c(state, other)
+            if (
+                opening_value <= 0.0
+                and number_count < 2
+                and number_sum < 0.5 * derived.open_target_sum
+                and deck_left > derived.mid_deck_threshold
+            ):
+                continue
+            forced_value = opening_value + 0.2 * number_sum
+            forced_value += <double>(state._state.min_rank + state._state.n_ranks - self._num_c(state, card))
+            if forced_value > best_value or (forced_value == best_value and 2 * slot > best_action):
+                best_value = forced_value
+                best_action = 2 * slot
+        return best_action
+
+    cdef int _best_discard_c(self, _CachedState state, int player, object derived) except -2:
+        cdef int opponent = 1 - player
+        cdef int slot
+        cdef int card
+        cdef double my_value
+        cdef double opponent_value
+        cdef double score
+        cdef double best_score = -1.0e100
+        cdef int best_action = -1
+        for slot in range(state.hand_size[player]):
+            if not self._legal_card_action_c(state, 2 * slot + 1):
+                continue
+            card = state.hand_encoded[player][slot]
+            my_value = self._card_value_for_me_c(state, player, card, derived)
+            opponent_value = self._card_value_for_opponent_c(state, opponent, card, derived)
+            score = -my_value - self.params.gift_penalty_weight * opponent_value
+            if not self._can_play_card_c(state, player, card):
+                score += self.params.unusable_discard_bonus
+            if not self._can_play_card_c(state, opponent, card):
+                score += self.params.discard_safety_bonus
+            if self._card_rank_c(state, card) == 0 and self._can_play_card_c(state, player, card):
+                score -= 4.0
+            if score > best_score or (score == best_score and 2 * slot + 1 > best_action):
+                best_score = score
+                best_action = 2 * slot + 1
+        return best_action
+
+    cdef double _visible_draw_value_c(
+        self, _CachedState state, int player, int card, object derived
+    ) except *:
+        cdef int color = self._card_color_c(state, card)
+        cdef int opponent = 1 - player
+        cdef int opened_colors = self._opened_colors_c(state, player)
+        cdef bint is_unopened_color = state.expedition_count[player][color] == 0
+        cdef double commitment = self._color_commitment_c(state, player, color, derived)
+        cdef double opponent_value = self._card_value_for_opponent_c(state, opponent, card, derived)
+        cdef int score_diff = state.total_scores[player] - state.total_scores[opponent]
+        cdef double value = self.params.deny_opponent_weight * opponent_value
+        cdef double support
+        cdef bint exceptional_support = False
+        cdef int slot
+        cdef int other
+        cdef int number_count
+        cdef int number_sum
+        cdef double required_sum
+        if score_diff <= 0:
+            value += self.params.losing_visible_draw_bonus
+        if is_unopened_color:
+            if opened_colors >= 4:
+                value -= self.params.unopened_draw_penalty_four_open
+            elif opened_colors >= 3:
+                value -= self.params.unopened_draw_penalty_three_open
+        if self._card_rank_c(state, card) == 0:
+            if self._has_numeric_c(state, player, color):
+                return value - self.params.dead_visible_draw_penalty
+            if state.expedition_count[player][color] == 0:
+                number_count = 0
+                number_sum = 0
+                for slot in range(state.hand_size[player]):
+                    other = state.hand_encoded[player][slot]
+                    if (
+                        self._card_color_c(state, other) == color
+                        and self._card_rank_c(state, other) != 0
+                        and self._can_play_card_c(state, player, other)
+                    ):
+                        number_count += 1
+                        number_sum += self._num_c(state, other)
+                required_sum = derived.open_target_sum * self.params.handshake_target_multiplier
+                if number_count < derived.min_handshake_numeric_cards or number_sum < required_sum:
+                    support = self._visible_open_support_value_c(state, player, card, derived)
+                    exceptional_support = support >= 6.0
+                    if (
+                        is_unopened_color
+                        and opened_colors >= 4
+                        and not exceptional_support
+                        and opponent_value < self.params.strong_deny_threshold
+                        and score_diff > -15
+                    ):
+                        return -8.0
+                    return value + support - 0.5
+            return value + 6.0 + commitment
+        if self._can_play_card_c(state, player, card):
+            value += self._num_c(state, card)
+            value += 0.7 * commitment
+            if state.expedition_count[player][color] > 0:
+                value += 5.0
+            else:
+                support = self._visible_open_support_value_c(state, player, card, derived)
+                exceptional_support = support >= 6.0
+                value += support
+        else:
+            value -= self.params.dead_visible_draw_penalty
+            if state.expedition_count[player][color] == 0:
+                support = self._visible_open_support_value_c(state, player, card, derived)
+                exceptional_support = support >= 6.0
+                value += support
+        if (
+            is_unopened_color
+            and opened_colors >= 4
+            and not exceptional_support
+            and opponent_value < self.params.strong_deny_threshold
+            and score_diff > -15
+        ):
+            return -8.0
+        value += self._bonus_potential_c(state, player, color, 1, derived, 0, -1)
+        return value
+
+    cdef double _visible_open_support_value_c(
+        self, _CachedState state, int player, int card, object derived
+    ) except *:
+        cdef int color = self._card_color_c(state, card)
+        cdef int opened_colors = self._opened_colors_c(state, player)
+        cdef int slot
+        cdef int other
+        cdef int rank
+        cdef int future_numbers = 0
+        cdef int same_color_handshakes = 0
+        cdef double value = 0.0
+        for slot in range(state.hand_size[player]):
+            other = state.hand_encoded[player][slot]
+            if self._card_color_c(state, other) != color:
+                continue
+            rank = self._card_rank_c(state, other)
+            if rank == 0:
+                same_color_handshakes += 1
+            elif other != card and rank >= self._card_rank_c(state, card):
+                future_numbers += 1
+        value += 0.8 * future_numbers
+        value += 1.0 * same_color_handshakes
+        if self._card_rank_c(state, card) <= derived.middle_rank:
+            value += self.params.speculative_visible_draw_bonus
+        if self._visible_number_can_help_open_c(state, player, card, derived):
+            value += 4.0
+        elif opened_colors <= 2 and (future_numbers > 0 or same_color_handshakes > 0):
+            value += self.params.speculative_visible_draw_bonus
+        if opened_colors <= 2:
+            value += 0.25 * self._opening_plan_value_c(
+                state, player, color, card, derived, state.deck_remaining
+            )
+        elif opened_colors == 3:
+            value += 0.1 * max(
+                0.0,
+                self._opening_plan_value_c(state, player, color, card, derived, state.deck_remaining),
+            )
+        return value
+
+    cdef bint _visible_number_can_help_open_c(
+        self, _CachedState state, int player, int card, object derived
+    ) except *:
+        cdef int color = self._card_color_c(state, card)
+        cdef int slot
+        cdef int other
+        cdef int count = 1
+        cdef int number_sum = self._num_c(state, card)
+        cdef bint has_high = self._card_rank_c(state, card) >= derived.middle_rank
+        for slot in range(state.hand_size[player]):
+            other = state.hand_encoded[player][slot]
+            if (
+                self._card_color_c(state, other) == color
+                and self._card_rank_c(state, other) != 0
+                and self._card_rank_c(state, other) >= self._card_rank_c(state, card)
+            ):
+                count += 1
+                number_sum += self._num_c(state, other)
+                if self._card_rank_c(state, other) >= derived.middle_rank:
+                    has_high = True
+        if count < derived.min_open_cards:
+            return False
+        if number_sum < derived.open_target_sum:
+            return False
+        return has_high
+
+    cdef double _deck_draw_value_c(self, _CachedState state, object derived) except *:
+        cdef int score_diff = state.total_scores[state.current_player] - state.total_scores[1 - state.current_player]
+        cdef double value
+        if state.deck_remaining > derived.mid_deck_threshold:
+            value = self.params.deck_draw_early_value
+        elif state.deck_remaining > derived.late_deck_threshold:
+            value = self.params.deck_draw_mid_value
+        else:
+            value = self.params.deck_draw_late_value
+        if score_diff > 0:
+            value += self.params.winning_deck_bonus
+        else:
+            value -= self.params.losing_deck_penalty
+        return value
+
+    cdef double _card_value_for_me_c(
+        self, _CachedState state, int player, int card, object derived
+    ) except *:
+        cdef int color = self._card_color_c(state, card)
+        cdef int rank = self._card_rank_c(state, card)
+        cdef double commitment
+        cdef int numeric_value
+        cdef double value
+        if not self._can_play_card_c(state, player, card):
+            return 0.0
+        commitment = self._color_commitment_c(state, player, color, derived)
+        if rank == 0:
+            return 7.0 + 1.2 * commitment
+        numeric_value = self._num_c(state, card)
+        value = 0.8 * numeric_value + self.params.commitment_weight * commitment
+        if state.expedition_count[player][color] > 0:
+            value += self.params.started_expedition_play_bonus
+            value += self.params.started_expedition_followup_bonus
+        if commitment >= 6.0 and rank <= derived.middle_rank:
+            value += self.params.low_card_sequence_bonus
+        return value
+
+    cdef double _card_value_for_opponent_c(
+        self, _CachedState state, int opponent, int card, object derived
+    ) except *:
+        cdef int rank = self._card_rank_c(state, card)
+        cdef double interest
+        if not self._can_play_card_c(state, opponent, card):
+            return 0.0
+        interest = self._public_color_commitment_for_opponent_c(
+            state, opponent, self._card_color_c(state, card), derived
+        )
+        if rank == 0:
+            return 8.0 + 1.5 * interest
+        return self._num_c(state, card) * (0.4 + 0.25 * interest)
+
+    cdef double _color_commitment_c(
+        self, _CachedState state, int player, int color, object derived
+    ) except *:
+        cdef int slot
+        cdef int card
+        cdef int rank
+        cdef int playable_numbers = 0
+        cdef int playable_handshakes = 0
+        cdef int playable_sum = 0
+        cdef double value
+        if self.color_commit_valid[player][color] != 0:
+            return self.color_commit_cache[player][color]
+        value = 0.0
+        if state.expedition_count[player][color] > 0:
+            value += 5.0
+        value += 2.0 * state.expedition_handshakes[player][color]
+        value += 0.25 * state.expedition_numeric_sum[player][color]
+        for slot in range(state.hand_size[player]):
+            card = state.hand_encoded[player][slot]
+            if self._card_color_c(state, card) != color or not self._can_play_card_c(state, player, card):
+                continue
+            rank = self._card_rank_c(state, card)
+            if rank == 0:
+                playable_handshakes += 1
+            else:
+                playable_numbers += 1
+                playable_sum += self._num_c(state, card)
+        value += 1.2 * playable_numbers
+        value += 1.5 * playable_handshakes
+        value += 0.15 * playable_sum
+        value += 0.05 * self._bonus_potential_c(state, player, color, 0, derived, 0, -1)
+        self.color_commit_cache[player][color] = value
+        self.color_commit_valid[player][color] = 1
+        return value
+
+    cdef double _public_color_commitment_for_opponent_c(
+        self, _CachedState state, int opponent, int color, object derived
+    ) except *:
+        cdef int top_card
+        cdef double value = 0.0
+        if state.expedition_count[opponent][color] > 0:
+            value += 5.0
+        value += 2.0 * state.expedition_handshakes[opponent][color]
+        value += 0.25 * state.expedition_numeric_sum[opponent][color]
+        if state.expedition_last_numeric[opponent][color] > 0:
+            value += 0.4 * (state.min_rank + state.expedition_last_numeric[opponent][color] - 1)
+        if state.discard_count[color] > 0:
+            top_card = state.discard_top[color]
+            if self._can_play_card_c(state, opponent, top_card):
+                if self._card_rank_c(state, top_card) == 0:
+                    value += 1.5
+                else:
+                    value += 1.0 + 0.1 * self._num_c(state, top_card)
+        if derived.bonus_possible and state.expedition_count[opponent][color] + 1 >= state.bonus_threshold:
+            value += 0.2 * state.bonus_amount
+        return value
+
+    cdef double _bonus_potential_c(
+        self,
+        _CachedState state,
+        int player,
+        int color,
+        int extra_cards,
+        object derived,
+        int committed_cards,
+        int exclude_card,
+    ) except *:
+        cdef int need
+        cdef int slot
+        cdef int card
+        cdef int playable_count = 0
+        if not derived.bonus_possible:
+            return 0.0
+        need = state.bonus_threshold - (state.expedition_count[player][color] + committed_cards)
+        if need <= 0:
+            return <double>state.bonus_amount
+        for slot in range(state.hand_size[player]):
+            card = state.hand_encoded[player][slot]
+            if (
+                card != exclude_card
+                and self._card_color_c(state, card) == color
+                and self._can_play_card_c(state, player, card)
+            ):
+                playable_count += 1
+        if playable_count + extra_cards >= need:
+            return 0.4 * state.bonus_amount
+        return 0.0
+
+    cdef double _new_color_open_penalty_c(self, int opened_colors) noexcept:
+        if opened_colors <= 1:
+            return 0.0
+        if opened_colors == 2:
+            return 6.0
+        if opened_colors == 3:
+            return 14.0
+        return 28.0
+
+    cdef double _late_penalty_c(self, object derived, int deck_left) except *:
+        if deck_left <= derived.late_deck_threshold:
+            return 15.0
+        if deck_left <= derived.mid_deck_threshold:
+            return 8.0
+        return 0.0
 
     def _act_card(self, state: GameState) -> int:
         player = state.current_player

src/coolrl_lost_cities/games/classic/ismcts/config.py

@@ -25,14 +25,26 @@ class MctsConfig(StrictModel):
     c_puct: float = 1.5
     max_depth: int = 200
     use_rollout_value: bool = True
+    rollout_policy: str = "random"
+    parallel_simulations: int = 8
+    virtual_loss_value: float = 1.0
+    eval_with_mcts: bool = True
+    eval_n_simulations: int = 0
 
-    @field_validator("n_simulations", "max_depth")
+    @field_validator("n_simulations", "max_depth", "parallel_simulations")
     @classmethod
     def _positive_int(cls, value: int) -> int:
         if value <= 0:
             raise ValueError("must be positive")
         return value
 
+    @field_validator("rollout_policy")
+    @classmethod
+    def _rollout_policy(cls, value: str) -> str:
+        if value not in {"random", "heuristic_balanced"}:
+            raise ValueError("rollout_policy must be 'random' or 'heuristic_balanced'")
+        return value
+
 
 class TemperatureConfig(StrictModel):
     training: float = 1.0
@@ -44,8 +56,20 @@ class TrainingConfig(StrictModel):
     gradient_steps_per_iter: int = 10
     batch_size: int = 128
     replay_capacity: int = 100_000
+    interleave_games: int = 8
+    interleave_max_batch: int = 64
+    num_workers: int = 1
+    worker_device: str = "cpu"
 
-    @field_validator("games_per_iter", "gradient_steps_per_iter", "batch_size", "replay_capacity")
+    @field_validator(
+        "games_per_iter",
+        "gradient_steps_per_iter",
+        "batch_size",
+        "replay_capacity",
+        "interleave_games",
+        "interleave_max_batch",
+        "num_workers",
+    )
     @classmethod
     def _positive_int(cls, value: int) -> int:
         if value <= 0:

src/coolrl_lost_cities/games/classic/ismcts/eval_worker.py

@@ -0,0 +1,125 @@
+"""Multi-process eval workers for ISMCTS — slice games across processes."""
+
+from __future__ import annotations
+
+import random
+from dataclasses import dataclass
+from typing import Any
+
+import torch
+
+from coolrl_lost_cities.games.classic.bots.registry import build_bot
+from coolrl_lost_cities.games.classic.deep_cfr.encoding import input_dim
+from coolrl_lost_cities.games.classic.game import GameState, LostCitiesConfig
+
+from .config import IsMctsConfig, config_from_dict
+from .mcts import IsMctsSearcher
+from .network import AlphaZeroNet
+
+
+@dataclass(frozen=True)
+class EvalWorkerBatch:
+    worker_index: int
+    config: dict[str, Any]
+    game_config: dict[str, Any]
+    network_state: dict[str, Any]
+    mcts_config: dict[str, Any]
+    opponent: str
+    game_indices: list[int]
+    seed: int
+    device: str
+    max_steps: int
+
+
+@dataclass
+class EvalWorkerResult:
+    worker_index: int
+    score_diffs: list[float]
+    wins0: int
+    wins1: int
+    draws: int
+    policy_turns: int
+    play_actions: int
+    timeouts: int
+
+
+def run_eval_worker(batch: EvalWorkerBatch) -> EvalWorkerResult:
+    import os
+
+    os.environ.setdefault("OMP_NUM_THREADS", "1")
+    os.environ.setdefault("MKL_NUM_THREADS", "1")
+    torch.set_num_threads(1)
+    cfg: IsMctsConfig = config_from_dict(batch.config)
+    game_config = LostCitiesConfig(**batch.game_config)
+    device = torch.device(batch.device)
+    probe = GameState.new_game(game_config, seed=batch.seed)
+    in_dim = input_dim(probe, cfg.encoding)
+    network = AlphaZeroNet.from_config(in_dim, probe.action_size, cfg).to(device)
+    network.load_state_dict(batch.network_state)
+    network.eval()
+    from .config import MctsConfig
+
+    mcts_config = MctsConfig.model_validate(batch.mcts_config)
+
+    rng = random.Random(batch.seed + batch.worker_index * 7919)
+    score_diffs: list[float] = []
+    wins0 = wins1 = draws = 0
+    policy_turns = 0
+    play_actions = 0
+    timeouts = 0
+    for game_index in batch.game_indices:
+        policy_player = game_index % 2
+        opponents = [
+            build_bot(batch.opponent, seed=batch.seed + game_index),
+            build_bot(batch.opponent, seed=batch.seed + game_index + 1),
+        ]
+        state = GameState.new_game(game_config, seed=batch.seed + game_index)
+        steps = 0
+        terminated = False
+        while steps < batch.max_steps:
+            if state.terminal:
+                terminated = True
+                break
+            current = int(state.current_player)
+            if current == policy_player:
+                searcher = IsMctsSearcher(
+                    network,
+                    mcts_config,
+                    device=device,
+                    encoding=cfg.encoding,
+                    rng=random.Random(rng.randrange(2**31)),
+                )
+                visits = searcher.search(state, current)
+                if visits:
+                    unified = max(visits, key=visits.get)
+                else:
+                    unified = state.unified_legal_actions()[0]
+                if state.phase == "card":
+                    policy_turns += 1
+                    if unified % 2 == 0:
+                        play_actions += 1
+                state.apply_unified_action(unified)
+            else:
+                action = opponents[current].act(state)
+                state.apply_action(action)
+            steps += 1
+        if not terminated:
+            timeouts += 1
+        diff = float(state.score_diff(policy_player))
+        score_diffs.append(diff)
+        if diff > 0:
+            wins0 += 1
+        elif diff < 0:
+            wins1 += 1
+        else:
+            draws += 1
+    return EvalWorkerResult(
+        worker_index=batch.worker_index,
+        score_diffs=score_diffs,
+        wins0=wins0,
+        wins1=wins1,
+        draws=draws,
+        policy_turns=policy_turns,
+        play_actions=play_actions,
+        timeouts=timeouts,
+    )

src/coolrl_lost_cities/games/classic/ismcts/evaluate.py

@@ -0,0 +1,190 @@
+from __future__ import annotations
+
+import multiprocessing as mp
+import random
+import time
+from concurrent.futures import ProcessPoolExecutor
+
+import torch
+
+from coolrl_lost_cities.games.classic.bots.registry import build_bot
+from coolrl_lost_cities.games.classic.game import GameState, LostCitiesConfig
+
+from .config import IsMctsConfig, MctsConfig
+from .eval_worker import EvalWorkerBatch, run_eval_worker
+from .mcts import IsMctsSearcher
+from .network import AlphaZeroNet
+
+
+def evaluate_with_mcts(
+    network: AlphaZeroNet,
+    game_config: LostCitiesConfig,
+    mcts_config: MctsConfig,
+    *,
+    games: int,
+    seed: int,
+    opponent: str,
+    device: torch.device | str = "cpu",
+    encoding=None,
+    max_steps: int = 10_000,
+    config: IsMctsConfig | None = None,
+    num_workers: int = 1,
+) -> dict[str, float | int]:
+    started = time.perf_counter()
+    if num_workers > 1 and config is not None and games > 1:
+        return _evaluate_parallel(
+            network,
+            game_config,
+            mcts_config,
+            config=config,
+            games=games,
+            seed=seed,
+            opponent=opponent,
+            num_workers=num_workers,
+            max_steps=max_steps,
+            started=started,
+        )
+    rng = random.Random(seed)
+    score_diffs: list[float] = []
+    wins0 = wins1 = draws = 0
+    policy_turns = 0
+    play_actions = 0
+    timeouts = 0
+
+    network.eval()
+    for game_index in range(games):
+        policy_player = game_index % 2
+        opponents = [
+            build_bot(opponent, seed=seed + game_index),
+            build_bot(opponent, seed=seed + game_index + 1),
+        ]
+        state = GameState.new_game(game_config, seed=seed + game_index)
+        steps = 0
+        terminated = False
+        while steps < max_steps:
+            if state.terminal:
+                terminated = True
+                break
+            current = int(state.current_player)
+            if current == policy_player:
+                searcher = IsMctsSearcher(
+                    network,
+                    mcts_config,
+                    device=device,
+                    encoding=encoding,
+                    rng=random.Random(rng.randrange(2**31)),
+                )
+                visits = searcher.search(state, current)
+                if visits:
+                    unified = max(visits, key=visits.get)
+                else:
+                    unified = state.unified_legal_actions()[0]
+                if state.phase == "card":
+                    policy_turns += 1
+                    if unified % 2 == 0:
+                        play_actions += 1
+                state.apply_unified_action(unified)
+            else:
+                action = opponents[current].act(state)
+                state.apply_action(action)
+            steps += 1
+        if not terminated:
+            timeouts += 1
+        diff = float(state.score_diff(policy_player))
+        score_diffs.append(diff)
+        if diff > 0:
+            wins0 += 1
+        elif diff < 0:
+            wins1 += 1
+        else:
+            draws += 1
+
+    n = len(score_diffs)
+    avg_diff = sum(score_diffs) / n if n else 0.0
+    return {
+        "games": n,
+        "win_rate0": wins0 / n if n else 0.0,
+        "win_rate1": wins1 / n if n else 0.0,
+        "wins0": wins0,
+        "wins1": wins1,
+        "draws": draws,
+        "avg_score_diff0": avg_diff,
+        "policy_turns": policy_turns,
+        "play_action_rate": play_actions / policy_turns if policy_turns else 0.0,
+        "max_step_timeouts": timeouts,
+        "elapsed_seconds": time.perf_counter() - started,
+    }
+
+
+def _evaluate_parallel(
+    network: AlphaZeroNet,
+    game_config: LostCitiesConfig,
+    mcts_config: MctsConfig,
+    *,
+    config: IsMctsConfig,
+    games: int,
+    seed: int,
+    opponent: str,
+    num_workers: int,
+    max_steps: int,
+    started: float,
+) -> dict[str, float | int]:
+    effective_workers = min(num_workers, games)
+    base = games // effective_workers
+    rem = games % effective_workers
+    counts = [base + (1 if i < rem else 0) for i in range(effective_workers)]
+    indices_per_worker: list[list[int]] = []
+    cursor = 0
+    for c in counts:
+        indices_per_worker.append(list(range(cursor, cursor + c)))
+        cursor += c
+    cpu_state = {name: tensor.detach().cpu() for name, tensor in network.state_dict().items()}
+    config_dict = config.to_dict()
+    game_snapshot = game_config.to_snapshot()
+    mcts_dict = mcts_config.model_dump(mode="json")
+    worker_device = str(config.training.worker_device)
+    batches = [
+        EvalWorkerBatch(
+            worker_index=i,
+            config=config_dict,
+            game_config=game_snapshot,
+            network_state=cpu_state,
+            mcts_config=mcts_dict,
+            opponent=opponent,
+            game_indices=indices_per_worker[i],
+            seed=seed,
+            device=worker_device,
+            max_steps=max_steps,
+        )
+        for i in range(effective_workers)
+    ]
+    ctx = mp.get_context("spawn")
+    score_diffs: list[float] = []
+    wins0 = wins1 = draws = 0
+    policy_turns = 0
+    play_actions = 0
+    timeouts = 0
+    with ProcessPoolExecutor(max_workers=effective_workers, mp_context=ctx) as executor:
+        for res in executor.map(run_eval_worker, batches):
+            score_diffs.extend(res.score_diffs)
+            wins0 += res.wins0
+            wins1 += res.wins1
+            draws += res.draws
+            policy_turns += res.policy_turns
+            play_actions += res.play_actions
+            timeouts += res.timeouts
+    n = len(score_diffs)
+    avg_diff = sum(score_diffs) / n if n else 0.0
+    return {
+        "games": n,
+        "win_rate0": wins0 / n if n else 0.0,
+        "win_rate1": wins1 / n if n else 0.0,
+        "wins0": wins0,
+        "wins1": wins1,
+        "draws": draws,
+        "avg_score_diff0": avg_diff,
+        "policy_turns": policy_turns,
+        "play_action_rate": play_actions / policy_turns if policy_turns else 0.0,
+        "max_step_timeouts": timeouts,
+        "elapsed_seconds": time.perf_counter() - started,
+    }

src/coolrl_lost_cities/games/classic/ismcts/info_set.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-import json
+import struct
 from collections import Counter
 
 from coolrl_lost_cities.games.classic.game import Card, GameState, build_deck
@@ -14,30 +14,73 @@ def _sorted_cards(cards: list[Card]) -> list[tuple[int, int]]:
     return sorted(_card_tuple(card) for card in cards)
 
 
+# Phase encoding: "card" -> 0, "draw" -> 1, anything else -> 2.
+_PHASE_TO_INT = {"card": 0, "draw": 1}
+
+
 def canonical_info_set_key(state: GameState, player: int) -> bytes:
-    """Deterministic key for observable information from ``player``'s POV."""
+    """Deterministic key for observable information from ``player``'s POV.
+
+    Packed binary representation (big-endian) covering the same fields as
+    the previous JSON encoding. Faster to compute and produces a more
+    compact key while remaining a stable, hashable ``bytes`` value.
+    """
     p = int(player)
-    payload = {
-        "config": state.config.to_snapshot(),
-        "player": p,
-        "current_player": int(state.current_player),
-        "phase": state.phase,
-        "pending_discarded_color": (
-            None if state.pending_discarded_color < 0 else int(state.pending_discarded_color)
-        ),
-        "turn_count": int(state.turn_count),
-        "terminal": bool(state.terminal),
-        "deck_size": len(state.deck),
-        "hand": _sorted_cards(state.hands[p]),
-        "hand_size_opp": len(state.hands[1 - p]),
-        "expeditions": [
-            [[_card_tuple(card) for card in expedition] for expedition in player_expeditions]
-            for player_expeditions in state.expeditions
-        ],
-        "discards": [[_card_tuple(card) for card in discard] for discard in state.discards],
-        "legal_mask": list(map(bool, state.unified_legal_mask())),
-    }
-    return json.dumps(payload, sort_keys=True, separators=(",", ":")).encode("utf-8")
+    cfg = state.config
+    parts: list[bytes] = []
+    # Header: rule constants that pin down the action/observation shape.
+    parts.append(
+        struct.pack(
+            ">BBBBBhhBBBBB",
+            int(cfg.n_colors) & 0xFF,
+            int(cfg.n_ranks) & 0xFF,
+            int(cfg.min_rank) & 0xFF,
+            int(cfg.n_handshakes) & 0xFF,
+            int(cfg.hand_size) & 0xFF,
+            int(cfg.expedition_penalty),
+            int(cfg.bonus_amount),
+            int(cfg.bonus_threshold) & 0xFF,
+            p & 0xFF,
+            int(state.current_player) & 0xFF,
+            _PHASE_TO_INT.get(state.phase, 2) & 0xFF,
+            (1 if state.terminal else 0) & 0xFF,
+        )
+    )
+    # Variable scalars.
+    pending_color = -1 if state.pending_discarded_color < 0 else int(state.pending_discarded_color)
+    parts.append(
+        struct.pack(
+            ">bHHH",
+            pending_color,
+            int(state.turn_count) & 0xFFFF,
+            len(state.deck) & 0xFFFF,
+            len(state.hands[1 - p]) & 0xFFFF,
+        )
+    )
+    # Sorted hand for the POV player. Cards encoded as (color, rank).
+    hand = state.hands[p]
+    parts.append(struct.pack(">H", len(hand)))
+    if hand:
+        sorted_pairs = sorted((int(c.color), int(c.rank)) for c in hand)
+        parts.append(b"".join(struct.pack(">BB", c, r) for c, r in sorted_pairs))
+    # Expeditions per player/color (ordered, since order matters for legality).
+    expeditions = state.expeditions
+    for player_expeditions in expeditions:
+        for expedition in player_expeditions:
+            parts.append(struct.pack(">H", len(expedition)))
+            if expedition:
+                parts.append(
+                    b"".join(struct.pack(">BB", int(c.color), int(c.rank)) for c in expedition)
+                )
+    # Discards per color.
+    for discard in state.discards:
+        parts.append(struct.pack(">H", len(discard)))
+        if discard:
+            parts.append(b"".join(struct.pack(">BB", int(c.color), int(c.rank)) for c in discard))
+    # Legal mask (packed as raw bytes from the underlying list).
+    mask = state.unified_legal_mask()
+    parts.append(bytes(1 if bool(b) else 0 for b in mask))
+    return b"".join(parts)
 
 
 def visible_cards(state: GameState, player: int) -> list[Card]:

src/coolrl_lost_cities/games/classic/ismcts/interleaved_self_play.py

@@ -0,0 +1,240 @@
+from __future__ import annotations
+
+import random
+from dataclasses import dataclass, field
+
+import numpy as np
+import torch
+
+from coolrl_lost_cities.games.classic.deep_cfr.encoding import encode_info_state
+from coolrl_lost_cities.games.classic.game import GameState, LostCitiesConfig
+
+from .config import MctsConfig, TrainingConfig
+from .info_set import canonical_info_set_key
+from .mcts import IsMctsSearcher, PendingSimulation
+from .network import AlphaZeroNet
+from .replay_buffer import ReplaySample
+from .self_play import select_from_distribution, visit_distribution
+
+
+@dataclass
+class _PendingDecision:
+    info_state: np.ndarray
+    legal_mask: np.ndarray
+    pi_target: np.ndarray
+    player: int
+    prior: np.ndarray
+    game_index: int
+
+
+@dataclass
+class _GameContext:
+    state: GameState
+    rng: random.Random
+    game_index: int
+    decisions: list[_PendingDecision] = field(default_factory=list)
+    steps: int = 0
+
+
+@dataclass
+class _SearchJob:
+    context: _GameContext
+    searcher: IsMctsSearcher
+    traverser: int
+    remaining: int
+
+
+def play_self_play_iteration(
+    network: AlphaZeroNet,
+    mcts_config: MctsConfig,
+    training_config: TrainingConfig,
+    game_config: LostCitiesConfig,
+    rng: random.Random,
+    *,
+    device: torch.device | str = "cpu",
+    encoding=None,
+    temperature: float = 1.0,
+    max_steps: int = 10_000,
+) -> list[ReplaySample]:
+    device = torch.device(device)
+    completed: list[list[ReplaySample]] = []
+    active: list[_GameContext] = []
+    started = 0
+    target_games = training_config.games_per_iter
+
+    def fill_active() -> None:
+        nonlocal started
+        while len(active) < training_config.interleave_games and started < target_games:
+            active.append(
+                _GameContext(
+                    state=GameState.new_game(game_config, seed=rng.randrange(2**31)),
+                    rng=random.Random(rng.randrange(2**31)),
+                    game_index=started,
+                )
+            )
+            started += 1
+
+    fill_active()
+    while active:
+        jobs: list[_SearchJob] = []
+        still_active: list[_GameContext] = []
+        for context in active:
+            if context.state.terminal or context.steps >= max_steps:
+                completed.append(_finalize_context(context))
+                continue
+            player = int(context.state.current_player)
+            searcher = IsMctsSearcher(
+                network,
+                mcts_config,
+                device=device,
+                encoding=encoding,
+                rng=random.Random(context.rng.randrange(2**31)),
+            )
+            jobs.append(
+                _SearchJob(
+                    context=context,
+                    searcher=searcher,
+                    traverser=player,
+                    remaining=mcts_config.n_simulations,
+                )
+            )
+            still_active.append(context)
+
+        active = still_active
+        if jobs:
+            _run_search_jobs(network, jobs, training_config.interleave_max_batch, device)
+            for job in jobs:
+                _finish_decision(job, mcts_config, encoding, temperature)
+
+        fill_active()
+
+    samples: list[ReplaySample] = []
+    for game_samples in completed:
+        samples.extend(game_samples)
+    return samples
+
+
+def _run_search_jobs(
+    network: AlphaZeroNet,
+    jobs: list[_SearchJob],
+    max_batch: int,
+    device: torch.device,
+) -> None:
+    while any(job.remaining > 0 for job in jobs):
+        pending: list[tuple[_SearchJob, PendingSimulation]] = []
+        for job in jobs:
+            job_quota = min(
+                job.remaining,
+                job.searcher.config.parallel_simulations,
+                max_batch - len(pending),
+            )
+            if job_quota <= 0:
+                break
+            job_pending = job.searcher.prepare_simulation_batch(
+                job.context.state,
+                job.traverser,
+                job_quota,
+            )
+            pending.extend((job, item) for item in job_pending)
+            job.remaining -= len(job_pending)
+            if len(pending) >= max_batch:
+                break
+        if not pending:
+            break
+        _evaluate_global_batch(network, pending, device)
+
+
+def _evaluate_global_batch(
+    network: AlphaZeroNet,
+    pending: list[tuple[_SearchJob, PendingSimulation]],
+    device: torch.device,
+) -> None:
+    network_pending = [(job, item) for job, item in pending if item.terminal_value is None]
+    values_by_id: dict[int, float] = {}
+    priors_by_id: dict[int, np.ndarray] = {}
+    if network_pending:
+        infos = np.stack(
+            [item.info_state for _job, item in network_pending if item.info_state is not None]
+        )
+        masks = np.stack(
+            [item.legal_mask for _job, item in network_pending if item.legal_mask is not None]
+        )
+        with torch.inference_mode():
+            x = torch.as_tensor(infos, dtype=torch.float32, device=device)
+            mask = torch.as_tensor(masks, dtype=torch.bool, device=device)
+            probs = network.policy_distribution(x, mask).detach().cpu().numpy()
+            _logits, values = network(x, mask)
+            values_np = values.detach().cpu().numpy()
+        for index, (_job, item) in enumerate(network_pending):
+            priors_by_id[id(item)] = probs[index]
+            values_by_id[id(item)] = float(values_np[index])
+
+    for job, item in pending:
+        if item.terminal_value is not None:
+            value = item.terminal_value
+        else:
+            assert item.leaf_node is not None
+            value = job.searcher._expand_with_prior(
+                item.leaf_node,
+                item.leaf_state,
+                item.leaf_player,
+                item.legal_actions,
+                priors_by_id[id(item)],
+                values_by_id[id(item)],
+            )
+        job.searcher._backup(item.path, value, item.leaf_player)
+
+
+def _finish_decision(
+    job: _SearchJob,
+    mcts_config: MctsConfig,
+    encoding,
+    temperature: float,
+) -> None:
+    context = job.context
+    state = context.state
+    player = int(state.current_player)
+    legal_mask = np.asarray(state.unified_legal_mask(), dtype=bool)
+    info = encode_info_state(state, player, encoding)
+    root_key = canonical_info_set_key(state, player)
+    root = job.searcher.tree.get_or_create(root_key, player=player, terminal=state.terminal)
+    visits = {action: root.visits.get(action, 0) for action in state.unified_legal_actions()}
+    pi = visit_distribution(visits, state.action_size, temperature=temperature)
+    if pi.sum() <= 0:
+        legal_actions = np.flatnonzero(legal_mask)
+        pi[legal_actions] = 1.0 / len(legal_actions)
+    prior = np.zeros(state.action_size, dtype=np.float32)
+    for action in state.unified_legal_actions():
+        prior[action] = float(root.priors.get(action, 0.0))
+    context.decisions.append(
+        _PendingDecision(
+            info_state=info.astype(np.float32),
+            legal_mask=legal_mask.astype(bool),
+            pi_target=pi.astype(np.float32),
+            player=player,
+            prior=prior,
+            game_index=context.game_index,
+        )
+    )
+    action = select_from_distribution(pi, context.rng)
+    state.apply_unified_action(action)
+    context.steps += 1
+
+
+def _finalize_context(context: _GameContext) -> list[ReplaySample]:
+    final_diff0 = float(context.state.score_diff(0))
+    samples: list[ReplaySample] = []
+    for decision in context.decisions:
+        value = final_diff0 if decision.player == 0 else -final_diff0
+        samples.append(
+            ReplaySample(
+                info_state=decision.info_state,
+                legal_mask=decision.legal_mask,
+                pi_target=decision.pi_target,
+                v_target=value,
+                player=decision.player,
+                prior=decision.prior,
+                game_index=decision.game_index,
+            )
+        )
+    return samples

src/coolrl_lost_cities/games/classic/ismcts/mcts.py

@@ -7,6 +7,7 @@ from dataclasses import dataclass, field
 import numpy as np
 import torch
 
+from coolrl_lost_cities.games.classic.bots.heuristic import HeuristicBot
 from coolrl_lost_cities.games.classic.deep_cfr.encoding import encode_info_state
 from coolrl_lost_cities.games.classic.game import GameState
 
@@ -23,6 +24,7 @@ class MctsNode:
     priors: dict[int, float] = field(default_factory=dict)
     visits: dict[int, int] = field(default_factory=dict)
     value_sum: dict[int, float] = field(default_factory=dict)
+    virtual_visits: dict[int, int] = field(default_factory=dict)
     children: dict[int, bytes] = field(default_factory=dict)
     terminal: bool = False
 
@@ -36,6 +38,26 @@ class MctsNode:
         return self.value_sum.get(action, 0.0) / n
 
 
+@dataclass
+class SearchPathEntry:
+    node: MctsNode
+    action: int
+    parent_player: int
+    child_player: int
+
+
+@dataclass
+class PendingSimulation:
+    path: list[SearchPathEntry]
+    leaf_state: GameState
+    leaf_node: MctsNode | None
+    leaf_player: int
+    info_state: np.ndarray | None
+    legal_mask: np.ndarray | None
+    legal_actions: list[int]
+    terminal_value: float | None = None
+
+
 class MctsTree:
     def __init__(self) -> None:
         self.nodes: dict[bytes, MctsNode] = {}
@@ -64,6 +86,9 @@ class IsMctsSearcher:
         self.encoding = encoding
         self.rng = rng or random.Random()
         self.tree = MctsTree()
+        self._rollout_bot = (
+            HeuristicBot() if config.rollout_policy == "heuristic_balanced" else None
+        )
 
     def search(
         self,
@@ -76,71 +101,209 @@ class IsMctsSearcher:
             root_key, player=state.current_player, terminal=state.terminal
         )
         sims = int(n_sims or self.config.n_simulations)
-        for _ in range(sims):
-            det = sample_determinization(state, traverser, self.rng)
-            self._simulate(det, depth=0)
+        completed = 0
+        while completed < sims:
+            batch_size = min(self.config.parallel_simulations, sims - completed)
+            pending = self.prepare_simulation_batch(state, traverser, batch_size)
+            if not pending:
+                break
+            self.evaluate_and_backup(pending)
+            completed += len(pending)
         legal = state.unified_legal_actions()
         return {action: root.visits.get(action, 0) for action in legal}
 
-    def _simulate(self, state: GameState, *, depth: int) -> float:
-        player = int(state.current_player)
-        if state.terminal or depth >= self.config.max_depth:
-            return float(state.score_diff(player))
+    def prepare_simulation_batch(
+        self,
+        root_state: GameState,
+        traverser: int,
+        max_simulations: int,
+    ) -> list[PendingSimulation]:
+        pending: list[PendingSimulation] = []
+        for _ in range(max_simulations):
+            item = self.prepare_simulation(root_state, traverser)
+            pending.append(item)
+            if item.terminal_value is None and item.leaf_node is not None and not item.path:
+                break
+        return pending
 
-        key = canonical_info_set_key(state, player)
-        node = self.tree.get_or_create(key, player=player, terminal=state.terminal)
-        if not node.is_expanded():
-            value = self._expand_and_evaluate(node, state, player)
-            return value
+    def prepare_simulation(self, root_state: GameState, traverser: int) -> PendingSimulation:
+        state = sample_determinization(root_state, traverser, self.rng)
+        path: list[SearchPathEntry] = []
+        depth = 0
+        # Cache the info-set key for the current node so we don't recompute it
+        # after applying an action (the child's key becomes the next iter's key).
+        cached_key: bytes | None = None
+        while True:
+            player = int(state.current_player)
+            if state.terminal or depth >= self.config.max_depth:
+                return PendingSimulation(
+                    path=path,
+                    leaf_state=state,
+                    leaf_node=None,
+                    leaf_player=player,
+                    info_state=None,
+                    legal_mask=None,
+                    legal_actions=[],
+                    terminal_value=float(state.score_diff(player)),
+                )
+            key = cached_key if cached_key is not None else canonical_info_set_key(state, player)
+            node = self.tree.get_or_create(key, player=player, terminal=state.terminal)
+            if not node.is_expanded():
+                legal_actions = state.unified_legal_actions()
+                if not legal_actions:
+                    node.terminal = True
+                    return PendingSimulation(
+                        path=path,
+                        leaf_state=state,
+                        leaf_node=node,
+                        leaf_player=player,
+                        info_state=None,
+                        legal_mask=None,
+                        legal_actions=[],
+                        terminal_value=float(state.score_diff(player)),
+                    )
+                return PendingSimulation(
+                    path=path,
+                    leaf_state=state,
+                    leaf_node=node,
+                    leaf_player=player,
+                    info_state=encode_info_state(state, player, self.encoding),
+                    legal_mask=np.asarray(state.unified_legal_mask(), dtype=bool),
+                    legal_actions=legal_actions,
+                )
 
-        action = self._select_action(node, state.unified_legal_actions())
-        child = state.clone()
-        child.apply_unified_action(action)
-        child_value = self._simulate(child, depth=depth + 1)
-        value = child_value if child.current_player == player else -child_value
-        node.visits[action] = node.visits.get(action, 0) + 1
-        node.value_sum[action] = node.value_sum.get(action, 0.0) + value
-        child_key = canonical_info_set_key(child, child.current_player)
-        node.children[action] = child_key
-        return value
+            # Reuse the same legal_actions list for selection (avoids one
+            # extra unified_legal_actions() call inside _select_action).
+            legal_actions = state.unified_legal_actions()
+            action = self._select_action(node, legal_actions)
+            node.virtual_visits[action] = node.virtual_visits.get(action, 0) + 1
+            child = state.clone()
+            child.apply_unified_action(action)
+            child_player = int(child.current_player)
+            child_key = canonical_info_set_key(child, child_player)
+            node.children[action] = child_key
+            path.append(
+                SearchPathEntry(
+                    node=node,
+                    action=action,
+                    parent_player=player,
+                    child_player=child_player,
+                )
+            )
+            state = child
+            cached_key = child_key
+            depth += 1
 
-    def _expand_and_evaluate(self, node: MctsNode, state: GameState, player: int) -> float:
+    def evaluate_and_backup(self, pending: list[PendingSimulation]) -> None:
+        network_pending = [item for item in pending if item.terminal_value is None]
+        values_by_id: dict[int, float] = {}
+        priors_by_id: dict[int, np.ndarray] = {}
+        if network_pending:
+            infos = np.stack(
+                [item.info_state for item in network_pending if item.info_state is not None]
+            )
+            masks = np.stack(
+                [item.legal_mask for item in network_pending if item.legal_mask is not None]
+            )
+            with torch.inference_mode():
+                x = torch.as_tensor(infos, dtype=torch.float32, device=self.device)
+                mask = torch.as_tensor(masks, dtype=torch.bool, device=self.device)
+                probs = self.network.policy_distribution(x, mask).detach().cpu().numpy()
+                _logits, network_values = self.network(x, mask)
+                network_values_np = network_values.detach().cpu().numpy()
+            for index, item in enumerate(network_pending):
+                priors_by_id[id(item)] = probs[index]
+                values_by_id[id(item)] = float(network_values_np[index])
+
+        for item in pending:
+            if item.terminal_value is not None:
+                value = item.terminal_value
+            else:
+                assert item.leaf_node is not None
+                value = self._expand_with_prior(
+                    item.leaf_node,
+                    item.leaf_state,
+                    item.leaf_player,
+                    item.legal_actions,
+                    priors_by_id[id(item)],
+                    values_by_id[id(item)],
+                )
+            self._backup(item.path, value, item.leaf_player)
+
+    def _expand_with_prior(
+        self,
+        node: MctsNode,
+        state: GameState,
+        player: int,
+        legal_actions: list[int],
+        probs: np.ndarray,
+        network_value: float,
+    ) -> float:
         legal_actions = state.unified_legal_actions()
         if not legal_actions:
             node.terminal = True
             return float(state.score_diff(player))
-        info = encode_info_state(state, player, self.encoding)
-        legal_mask = np.asarray(state.unified_legal_mask(), dtype=bool)
-        with torch.inference_mode():
-            x = torch.as_tensor(info[None, :], dtype=torch.float32, device=self.device)
-            mask = torch.as_tensor(legal_mask[None, :], dtype=torch.bool, device=self.device)
-            probs = self.network.policy_distribution(x, mask).squeeze(0).detach().cpu().numpy()
-            _logits, network_value = self.network(x, mask)
         for action in legal_actions:
             node.priors[action] = float(probs[action])
             node.visits.setdefault(action, 0)
             node.value_sum.setdefault(action, 0.0)
+            node.virtual_visits.setdefault(action, 0)
         rollout_value = (
             self._rollout_value(state, player) if self.config.use_rollout_value else None
         )
         if rollout_value is None:
-            return float(network_value.item())
+            return float(network_value)
         return rollout_value
 
     def _select_action(self, node: MctsNode, legal_actions: list[int]) -> int:
-        total_visits = sum(node.visits.get(action, 0) for action in legal_actions)
+        total_visits = sum(
+            node.visits.get(action, 0) + node.virtual_visits.get(action, 0)
+            for action in legal_actions
+        )
         sqrt_total = math.sqrt(max(1, total_visits))
         best_score = -float("inf")
         best_action = legal_actions[0]
         for action in legal_actions:
             n = node.visits.get(action, 0)
+            virtual = node.virtual_visits.get(action, 0)
+            n_eff = n + virtual
             prior = node.priors.get(action, 0.0)
-            score = node.q(action) + self.config.c_puct * prior * sqrt_total / (1 + n)
+            if n_eff <= 0:
+                q_eff = 0.0
+            else:
+                q_eff = (
+                    node.value_sum.get(action, 0.0) - virtual * self.config.virtual_loss_value
+                ) / n_eff
+            score = q_eff + self.config.c_puct * prior * sqrt_total / (1 + n_eff)
             if score > best_score:
                 best_score = score
                 best_action = action
         return int(best_action)
 
+    def _backup(
+        self,
+        path: list[SearchPathEntry],
+        leaf_value: float,
+        leaf_player: int,
+    ) -> None:
+        value = float(leaf_value)
+        value_player = int(leaf_player)
+        for entry in reversed(path):
+            parent_value = value if value_player == entry.parent_player else -value
+            current_virtual = entry.node.virtual_visits.get(entry.action, 0)
+            entry.node.virtual_visits[entry.action] = max(0, current_virtual - 1)
+            entry.node.visits[entry.action] = entry.node.visits.get(entry.action, 0) + 1
+            entry.node.value_sum[entry.action] = (
+                entry.node.value_sum.get(entry.action, 0.0) + parent_value
+            )
+            value = parent_value
+            value_player = entry.parent_player
+
+    def _release_virtual_path(self, path: list[SearchPathEntry]) -> None:
+        for entry in path:
+            current_virtual = entry.node.virtual_visits.get(entry.action, 0)
+            entry.node.virtual_visits[entry.action] = max(0, current_virtual - 1)
+
     def _rollout_value(self, state: GameState, player: int) -> float | None:
         rollout = state.clone()
         steps = 0
@@ -148,7 +311,13 @@ class IsMctsSearcher:
             legal = rollout.unified_legal_actions()
             if not legal:
                 break
-            action = self.rng.choice(legal)
+            if self._rollout_bot is not None:
+                phase_action = self._rollout_bot.act(rollout)
+                action = rollout.to_unified_action(phase_action)
+                if action not in legal:
+                    action = self.rng.choice(legal)
+            else:
+                action = self.rng.choice(legal)
             rollout.apply_unified_action(action)
             steps += 1
         return float(rollout.score_diff(player))

src/coolrl_lost_cities/games/classic/ismcts/mcts.pyx

@@ -0,0 +1,621 @@
+# cython: language_level=3, boundscheck=False, wraparound=False, cdivision=True, initializedcheck=False
+from __future__ import annotations
+
+import math
+import random
+
+import numpy as np
+import torch
+
+from coolrl_lost_cities.games.classic.bots.heuristic_cy cimport HeuristicBot
+from coolrl_lost_cities.games.classic.bots.heuristic import HeuristicBot as PyHeuristicBot
+from coolrl_lost_cities.games.classic.deep_cfr.encoding import encode_info_state
+from coolrl_lost_cities.games.classic.game cimport GameState
+
+from .determinization import sample_determinization
+from .info_set import canonical_info_set_key
+
+
+DEF MAX_ACTIONS = 64
+DEF DEFAULT_ACTION_SIZE = 64
+
+
+cdef class _ArrayMap:
+    cdef MctsNode node
+    cdef int kind
+    cdef int action_size
+    cdef bint is_int
+
+    def __init__(self, MctsNode node, int kind, bint is_int=False):
+        self.node = node
+        self.kind = kind
+        self.action_size = node.action_size
+        self.is_int = is_int
+
+    cdef inline void _check(self, int action) except *:
+        if action < 0 or action >= self.action_size:
+            raise KeyError(action)
+
+    cdef inline bint has(self, int action) noexcept:
+        return 0 <= action < self.action_size and self.node.active_present[action] != 0
+
+    cdef inline long get_int(self, int action, long default_value=0) noexcept:
+        if 0 <= action < self.action_size and self.node.active_present[action] != 0:
+            if self.kind == 1:
+                return self.node.visits_arr[action]
+            if self.kind == 3:
+                return self.node.virtual_visits_arr[action]
+        return default_value
+
+    cdef inline double get_float(self, int action, double default_value=0.0) noexcept:
+        if 0 <= action < self.action_size and self.node.active_present[action] != 0:
+            if self.kind == 0:
+                return self.node.priors_arr[action]
+            if self.kind == 2:
+                return self.node.value_sum_arr[action]
+        return default_value
+
+    cdef inline void _mark_active(self, int action) noexcept:
+        if self.node.active_present[action] == 0:
+            self.node.active_present[action] = 1
+            self.node.active_actions[self.node.n_active] = action
+            self.node.n_active += 1
+
+    cdef inline void set_int(self, int action, long value) except *:
+        self._check(action)
+        self._mark_active(action)
+        if self.kind == 1:
+            self.node.visits_arr[action] = <int>value
+        elif self.kind == 3:
+            self.node.virtual_visits_arr[action] = <int>value
+        else:
+            raise TypeError("integer write to float node map")
+
+    cdef inline void set_float(self, int action, double value) except *:
+        self._check(action)
+        self._mark_active(action)
+        if self.kind == 0:
+            self.node.priors_arr[action] = value
+        elif self.kind == 2:
+            self.node.value_sum_arr[action] = value
+        else:
+            raise TypeError("float write to integer node map")
+
+    def get(self, action, default=None):
+        cdef int a = int(action)
+        if self.has(a):
+            if self.is_int:
+                return int(self.get_int(a, 0))
+            return float(self.get_float(a, 0.0))
+        return default
+
+    def setdefault(self, action, default=None):
+        cdef int a = int(action)
+        if self.has(a):
+            if self.is_int:
+                return int(self.get_int(a, 0))
+            return float(self.get_float(a, 0.0))
+        if default is None:
+            default = 0 if self.is_int else 0.0
+        if self.is_int:
+            self.set_int(a, int(default))
+            return int(default)
+        self.set_float(a, float(default))
+        return float(default)
+
+    def __getitem__(self, action):
+        cdef int a = int(action)
+        self._check(a)
+        if self.node.active_present[a] == 0:
+            raise KeyError(action)
+        if self.is_int:
+            return int(self.get_int(a, 0))
+        return float(self.get_float(a, 0.0))
+
+    def __setitem__(self, action, value):
+        cdef int a = int(action)
+        if self.is_int:
+            self.set_int(a, int(value))
+        else:
+            self.set_float(a, float(value))
+
+    def __contains__(self, action):
+        return self.has(int(action))
+
+    def __bool__(self):
+        return self.node.n_active > 0
+
+    def __len__(self):
+        return self.node.n_active
+
+    def items(self):
+        cdef int i
+        result = []
+        cdef int action
+        for i in range(self.node.n_active):
+            action = self.node.active_actions[i]
+            if self.is_int:
+                result.append((action, int(self.get_int(action, 0))))
+            else:
+                result.append((action, float(self.get_float(action, 0.0))))
+        return result
+
+    def keys(self):
+        cdef int i
+        return [self.node.active_actions[i] for i in range(self.node.n_active)]
+
+    def values(self):
+        cdef int i
+        result = []
+        cdef int action
+        for i in range(self.node.n_active):
+            action = self.node.active_actions[i]
+            if self.is_int:
+                result.append(int(self.get_int(action, 0)))
+            else:
+                result.append(float(self.get_float(action, 0.0)))
+        return result
+
+    def __repr__(self):
+        return repr(dict(self.items()))
+
+
+cdef class MctsNode:
+    cdef public bytes info_set_key
+    cdef public int player
+    cdef public object priors
+    cdef public object visits
+    cdef public object value_sum
+    cdef public object virtual_visits
+    cdef public dict children
+    cdef public bint terminal
+    cdef public bint expanded
+    cdef int action_size
+    cdef int visits_arr[MAX_ACTIONS]
+    cdef double value_sum_arr[MAX_ACTIONS]
+    cdef double priors_arr[MAX_ACTIONS]
+    cdef int virtual_visits_arr[MAX_ACTIONS]
+    cdef int active_actions[MAX_ACTIONS]
+    cdef unsigned char active_present[MAX_ACTIONS]
+    cdef int n_active
+
+    def __init__(
+        self,
+        bytes info_set_key,
+        int player,
+        object priors=None,
+        object visits=None,
+        object value_sum=None,
+        object virtual_visits=None,
+        object children=None,
+        bint terminal=False,
+        int action_size=DEFAULT_ACTION_SIZE,
+    ):
+        if action_size > MAX_ACTIONS:
+            raise ValueError("action_size exceeds fixed MCTS action buffer")
+        self.info_set_key = info_set_key
+        self.player = player
+        self.terminal = terminal
+        self.expanded = terminal
+        self.action_size = action_size
+        self.n_active = 0
+        self.priors = _ArrayMap(self, 0, False)
+        self.visits = _ArrayMap(self, 1, True)
+        self.value_sum = _ArrayMap(self, 2, False)
+        self.virtual_visits = _ArrayMap(self, 3, True)
+        self.children = {} if children is None else dict(children)
+        if priors is not None:
+            for action, value in dict(priors).items():
+                self.priors[action] = value
+        if visits is not None:
+            for action, value in dict(visits).items():
+                self.visits[action] = value
+        if value_sum is not None:
+            for action, value in dict(value_sum).items():
+                self.value_sum[action] = value
+        if virtual_visits is not None:
+            for action, value in dict(virtual_visits).items():
+                self.virtual_visits[action] = value
+
+    cpdef bint is_expanded(self):
+        return self.terminal or self.expanded or self.n_active > 0
+
+    cpdef double q(self, int action):
+        cdef long n = (<_ArrayMap>self.visits).get_int(action, 0)
+        if n <= 0:
+            return 0.0
+        return (<_ArrayMap>self.value_sum).get_float(action, 0.0) / n
+
+
+cdef class SearchPathEntry:
+    cdef public MctsNode node
+    cdef public int action
+    cdef public int parent_player
+    cdef public int child_player
+
+    def __init__(self, MctsNode node, int action, int parent_player, int child_player):
+        self.node = node
+        self.action = action
+        self.parent_player = parent_player
+        self.child_player = child_player
+
+
+cdef class PendingSimulation:
+    cdef public list path
+    cdef public GameState leaf_state
+    cdef public object leaf_node
+    cdef public int leaf_player
+    cdef public object info_state
+    cdef public object legal_mask
+    cdef public list legal_actions
+    cdef public object terminal_value
+
+    def __init__(
+        self,
+        list path,
+        GameState leaf_state,
+        object leaf_node,
+        int leaf_player,
+        object info_state,
+        object legal_mask,
+        list legal_actions,
+        object terminal_value=None,
+    ):
+        self.path = path
+        self.leaf_state = leaf_state
+        self.leaf_node = leaf_node
+        self.leaf_player = leaf_player
+        self.info_state = info_state
+        self.legal_mask = legal_mask
+        self.legal_actions = legal_actions
+        self.terminal_value = terminal_value
+
+
+cdef class MctsTree:
+    cdef public dict nodes
+    cdef int action_size
+
+    def __init__(self, int action_size=DEFAULT_ACTION_SIZE):
+        self.nodes = {}
+        self.action_size = action_size
+
+    def get_or_create(self, bytes key, *, int player, bint terminal=False):
+        cdef MctsNode node = self.nodes.get(key)
+        if node is None:
+            node = MctsNode(key, player=player, terminal=terminal, action_size=self.action_size)
+            self.nodes[key] = node
+        return node
+
+
+cdef class IsMctsSearcher:
+    cdef public object network
+    cdef public object config
+    cdef public object device
+    cdef public object encoding
+    cdef public object rng
+    cdef public MctsTree tree
+    cdef HeuristicBot _rollout_bot
+    cdef int action_size
+
+    def __init__(
+        self,
+        object network,
+        object config,
+        *,
+        object device="cpu",
+        object encoding=None,
+        object rng=None,
+    ):
+        self.network = network
+        self.config = config
+        self.device = torch.device(device)
+        self.encoding = encoding
+        self.rng = rng or random.Random()
+        self.action_size = int(getattr(network, "action_size", DEFAULT_ACTION_SIZE))
+        if self.action_size > MAX_ACTIONS:
+            raise ValueError("action_size exceeds fixed MCTS action buffer")
+        self.tree = MctsTree(self.action_size)
+        self._rollout_bot = (
+            <HeuristicBot>PyHeuristicBot() if config.rollout_policy == "heuristic_balanced" else None
+        )
+
+    cdef inline int _from_unified_action_c(self, GameState state, int action_id) noexcept:
+        cdef int card_action_size = 2 * state.hand_size
+        if state.phase_id == 0:
+            return action_id
+        return action_id - card_action_size
+
+    cdef list _unified_legal_actions_list_c(self, GameState state):
+        cdef int actions[MAX_ACTIONS]
+        cdef int count = state._unified_legal_actions_c(actions)
+        cdef int i
+        return [actions[i] for i in range(count)]
+
+    cpdef dict search(self, GameState state, int traverser, object n_sims=None):
+        cdef bytes root_key = canonical_info_set_key(state, state.current_player)
+        cdef MctsNode root = self.tree.get_or_create(
+            root_key, player=state.current_player, terminal=state.terminal
+        )
+        cdef int sims = int(n_sims or self.config.n_simulations)
+        cdef int completed = 0
+        cdef list pending
+        cdef list legal
+        cdef int action
+        cdef dict result
+        while completed < sims:
+            pending = self.prepare_simulation_batch(state, traverser, 1)
+            if not pending:
+                break
+            self.evaluate_and_backup(pending)
+            completed += len(pending)
+        legal = state.unified_legal_actions()
+        result = {}
+        for action in legal:
+            result[action] = (<_ArrayMap>root.visits).get_int(action, 0)
+        return result
+
+    cpdef list prepare_simulation_batch(
+        self,
+        GameState root_state,
+        int traverser,
+        int max_simulations,
+    ):
+        cdef list pending = []
+        cdef PendingSimulation item
+        cdef int i
+        for i in range(max_simulations):
+            item = self.prepare_simulation(root_state, traverser)
+            pending.append(item)
+            if item.terminal_value is None and item.leaf_node is not None and not item.path:
+                break
+        return pending
+
+    cpdef PendingSimulation prepare_simulation(self, GameState root_state, int traverser):
+        cdef GameState state = sample_determinization(root_state, traverser, self.rng)
+        cdef list path = []
+        cdef int depth = 0
+        cdef object cached_key = None
+        cdef int player
+        cdef bytes key
+        cdef MctsNode node
+        cdef list legal_actions
+        cdef int action
+        cdef int local_action
+        cdef int child_player
+        cdef bytes child_key
+        cdef int actions[MAX_ACTIONS]
+        cdef int action_count
+        cdef int i
+        while True:
+            player = state.current_player
+            if state.terminal or depth >= int(self.config.max_depth):
+                return PendingSimulation(
+                    path=path,
+                    leaf_state=state,
+                    leaf_node=None,
+                    leaf_player=player,
+                    info_state=None,
+                    legal_mask=None,
+                    legal_actions=[],
+                    terminal_value=float(state.total_scores[player] - state.total_scores[1 - player]),
+                )
+            if cached_key is None:
+                key = canonical_info_set_key(state, player)
+            else:
+                key = cached_key
+            node = self.tree.get_or_create(key, player=player, terminal=state.terminal)
+            if not node.is_expanded():
+                action_count = state._unified_legal_actions_c(actions)
+                legal_actions = [actions[i] for i in range(action_count)]
+                if not legal_actions:
+                    node.terminal = True
+                    return PendingSimulation(
+                        path=path,
+                        leaf_state=state,
+                        leaf_node=node,
+                        leaf_player=player,
+                        info_state=None,
+                        legal_mask=None,
+                        legal_actions=[],
+                        terminal_value=float(state.total_scores[player] - state.total_scores[1 - player]),
+                    )
+                return PendingSimulation(
+                    path=path,
+                    leaf_state=state,
+                    leaf_node=node,
+                    leaf_player=player,
+                    info_state=encode_info_state(state, player, self.encoding),
+                    legal_mask=np.asarray(state.unified_legal_mask(), dtype=bool),
+                    legal_actions=legal_actions,
+                )
+
+            action_count = state._unified_legal_actions_c(actions)
+            legal_actions = [actions[i] for i in range(action_count)]
+            action = self._select_action(node, legal_actions)
+            (<_ArrayMap>node.virtual_visits).set_int(
+                action, (<_ArrayMap>node.virtual_visits).get_int(action, 0) + 1
+            )
+            local_action = self._from_unified_action_c(state, action)
+            state._push_action_c(local_action)
+            child_player = state.current_player
+            child_key = canonical_info_set_key(state, child_player)
+            node.children[action] = child_key
+            path.append(
+                SearchPathEntry(
+                    node=node,
+                    action=action,
+                    parent_player=player,
+                    child_player=child_player,
+                )
+            )
+            cached_key = child_key
+            depth += 1
+
+    cpdef evaluate_and_backup(self, list pending):
+        cdef list network_pending = [item for item in pending if item.terminal_value is None]
+        cdef dict values_by_id = {}
+        cdef dict priors_by_id = {}
+        cdef object infos
+        cdef object masks
+        cdef object x
+        cdef object mask
+        cdef object probs
+        cdef object network_values
+        cdef object network_values_np
+        cdef int index
+        cdef PendingSimulation item
+        cdef double value
+        if network_pending:
+            infos = np.stack([item.info_state for item in network_pending if item.info_state is not None])
+            masks = np.stack([item.legal_mask for item in network_pending if item.legal_mask is not None])
+            with torch.inference_mode():
+                x = torch.as_tensor(infos, dtype=torch.float32, device=self.device)
+                mask = torch.as_tensor(masks, dtype=torch.bool, device=self.device)
+                probs = self.network.policy_distribution(x, mask).detach().cpu().numpy()
+                _logits, network_values = self.network(x, mask)
+                network_values_np = network_values.detach().cpu().numpy()
+            for index, item in enumerate(network_pending):
+                priors_by_id[id(item)] = probs[index]
+                values_by_id[id(item)] = float(network_values_np[index])
+
+        for item in pending:
+            if item.terminal_value is not None:
+                value = item.terminal_value
+            else:
+                value = self._expand_with_prior(
+                    item.leaf_node,
+                    item.leaf_state,
+                    item.leaf_player,
+                    item.legal_actions,
+                    priors_by_id[id(item)],
+                    values_by_id[id(item)],
+                )
+            self._backup(item.path, value, item.leaf_player)
+
+    cpdef double _expand_with_prior(
+        self,
+        MctsNode node,
+        GameState state,
+        int player,
+        list legal_actions,
+        object probs,
+        double network_value,
+    ):
+        cdef int action
+        cdef object rollout_value
+        legal_actions = self._unified_legal_actions_list_c(state)
+        if not legal_actions:
+            node.terminal = True
+            return float(state.total_scores[player] - state.total_scores[1 - player])
+        node.expanded = True
+        for action in legal_actions:
+            (<_ArrayMap>node.priors).set_float(action, float(probs[action]))
+            if not (<_ArrayMap>node.visits).has(action):
+                (<_ArrayMap>node.visits).set_int(action, 0)
+            if not (<_ArrayMap>node.value_sum).has(action):
+                (<_ArrayMap>node.value_sum).set_float(action, 0.0)
+            if not (<_ArrayMap>node.virtual_visits).has(action):
+                (<_ArrayMap>node.virtual_visits).set_int(action, 0)
+        rollout_value = self._rollout_value(state, player) if self.config.use_rollout_value else None
+        if rollout_value is None:
+            return float(network_value)
+        return float(rollout_value)
+
+    cpdef int _select_action(self, MctsNode node, list legal_actions):
+        cdef int total_visits = 0
+        cdef int action
+        cdef long n
+        cdef long virtual
+        cdef long n_eff
+        cdef double sqrt_total
+        cdef double prior
+        cdef double q_eff
+        cdef double score
+        cdef double best_score = -float("inf")
+        cdef int best_action = int(legal_actions[0])
+        cdef _ArrayMap visits = <_ArrayMap>node.visits
+        cdef _ArrayMap virtual_visits = <_ArrayMap>node.virtual_visits
+        cdef _ArrayMap priors = <_ArrayMap>node.priors
+        cdef _ArrayMap value_sum = <_ArrayMap>node.value_sum
+        for action in legal_actions:
+            total_visits += visits.get_int(action, 0) + virtual_visits.get_int(action, 0)
+        sqrt_total = math.sqrt(max(1, total_visits))
+        for action in legal_actions:
+            n = visits.get_int(action, 0)
+            virtual = virtual_visits.get_int(action, 0)
+            n_eff = n + virtual
+            prior = priors.get_float(action, 0.0)
+            if n_eff <= 0:
+                q_eff = 0.0
+            else:
+                q_eff = (
+                    value_sum.get_float(action, 0.0)
+                    - virtual * float(self.config.virtual_loss_value)
+                ) / n_eff
+            score = q_eff + float(self.config.c_puct) * prior * sqrt_total / (1 + n_eff)
+            if score > best_score:
+                best_score = score
+                best_action = action
+        return int(best_action)
+
+    cpdef _backup(self, list path, double leaf_value, int leaf_player):
+        cdef double value = float(leaf_value)
+        cdef int value_player = int(leaf_player)
+        cdef SearchPathEntry entry
+        cdef double parent_value
+        cdef long current_virtual
+        cdef _ArrayMap visits
+        cdef _ArrayMap virtual_visits
+        cdef _ArrayMap value_sum
+        for entry in reversed(path):
+            parent_value = value if value_player == entry.parent_player else -value
+            virtual_visits = <_ArrayMap>entry.node.virtual_visits
+            visits = <_ArrayMap>entry.node.visits
+            value_sum = <_ArrayMap>entry.node.value_sum
+            current_virtual = virtual_visits.get_int(entry.action, 0)
+            virtual_visits.set_int(entry.action, max(0, current_virtual - 1))
+            visits.set_int(entry.action, visits.get_int(entry.action, 0) + 1)
+            value_sum.set_float(
+                entry.action,
+                value_sum.get_float(entry.action, 0.0) + parent_value,
+            )
+            value = parent_value
+            value_player = entry.parent_player
+
+    cpdef _release_virtual_path(self, list path):
+        cdef SearchPathEntry entry
+        cdef _ArrayMap virtual_visits
+        cdef long current_virtual
+        for entry in path:
+            virtual_visits = <_ArrayMap>entry.node.virtual_visits
+            current_virtual = virtual_visits.get_int(entry.action, 0)
+            virtual_visits.set_int(entry.action, max(0, current_virtual - 1))
+
+    cpdef object _rollout_value(self, GameState state, int player):
+        cdef int steps = 0
+        cdef int actions[MAX_ACTIONS]
+        cdef int count
+        cdef int unified_action
+        cdef int action
+        cdef int max_depth = int(self.config.max_depth)
+        while not state.terminal and steps < max_depth:
+            if self._rollout_bot is not None:
+                action = self._rollout_bot.act_cython(state)
+                if not state._is_legal_action_c(action):
+                    count = state._unified_legal_actions_c(actions)
+                    if count <= 0:
+                        break
+                    unified_action = actions[self.rng.randrange(count)]
+                    action = self._from_unified_action_c(state, unified_action)
+            else:
+                count = state._unified_legal_actions_c(actions)
+                if count <= 0:
+                    break
+                unified_action = actions[self.rng.randrange(count)]
+                action = self._from_unified_action_c(state, unified_action)
+            state._push_action_c(action)
+            steps += 1
+        while steps > 0:
+            state._pop_action_c()
+            steps -= 1
+        return float(state.total_scores[player] - state.total_scores[1 - player])

src/coolrl_lost_cities/games/classic/ismcts/replay_buffer.py

@@ -15,6 +15,7 @@ class ReplaySample:
     v_target: float
     player: int
     prior: np.ndarray | None = None
+    game_index: int | None = None
 
 
 class ReplayBuffer:

src/coolrl_lost_cities/games/classic/ismcts/trainer.py

@@ -1,8 +1,10 @@
 from __future__ import annotations
 
 import json
+import multiprocessing as mp
 import random
 import time
+from concurrent.futures import ProcessPoolExecutor
 from dataclasses import dataclass
 from pathlib import Path
 
@@ -15,9 +17,11 @@ from coolrl_lost_cities.games.classic.deep_cfr.evaluate import evaluate_strategy
 from coolrl_lost_cities.games.classic.game import GameState, LostCitiesConfig
 
 from .config import IsMctsConfig
+from .evaluate import evaluate_with_mcts
+from .interleaved_self_play import play_self_play_iteration
 from .network import AlphaZeroLogitsView, AlphaZeroNet
 from .replay_buffer import ReplayBuffer, ReplaySample
-from .self_play import play_self_play_game
+from .workers import SelfPlayWorkerBatch, run_self_play_worker
 
 
 @dataclass
@@ -112,14 +116,19 @@ class IsMctsTrainer:
         return metrics
 
     def run_iteration(self, iteration: int) -> IterationMetrics:
+        print(
+            f"[iter {iteration}] self-play start (workers={self.config.training.num_workers})",
+            flush=True,
+        )
         self.network.eval()
         sp_started = time.perf_counter()
-        added = 0
-        iteration_samples: list[ReplaySample] = []
-        for _ in range(self.config.training.games_per_iter):
-            samples = play_self_play_game(
+        if self.config.training.num_workers > 1:
+            iteration_samples = self._run_self_play_parallel(iteration)
+        else:
+            iteration_samples = play_self_play_iteration(
                 self.network,
                 self.config.mcts,
+                self.config.training,
                 self.game_config,
                 self.rng,
                 device=self.device,
@@ -127,10 +136,13 @@ class IsMctsTrainer:
                 temperature=self.config.temperature.training,
                 max_steps=self.config.evaluation.max_steps,
             )
-            self.buffer.add(samples)
-            iteration_samples.extend(samples)
-            added += len(samples)
+        self.buffer.add(iteration_samples)
+        added = len(iteration_samples)
         self_play_seconds = time.perf_counter() - sp_started
+        print(
+            f"[iter {iteration}] self-play done in {self_play_seconds:.1f}s, {added} samples",
+            flush=True,
+        )
         mcts_metrics = self._compute_mcts_metrics(iteration_samples)
 
         train_started = time.perf_counter()
@@ -140,7 +152,12 @@ class IsMctsTrainer:
             losses.append(self._train_batch(batch))
         train_seconds = time.perf_counter() - train_started
         loss_arr = np.asarray(losses, dtype=np.float64)
+        print(f"[iter {iteration}] train done in {train_seconds:.1f}s, eval starting", flush=True)
+        eval_started = time.perf_counter()
         eval_metrics = self._evaluate(iteration)
+        print(
+            f"[iter {iteration}] eval done in {time.perf_counter() - eval_started:.1f}s", flush=True
+        )
         return IterationMetrics(
             iteration=iteration,
             samples_added=added,
@@ -154,6 +171,69 @@ class IsMctsTrainer:
             mcts_metrics=mcts_metrics,
         )
 
+    def _run_self_play_parallel(self, iteration: int) -> list[ReplaySample]:
+        training_cfg = self.config.training
+        num_workers = max(1, int(training_cfg.num_workers))
+        total_games = int(training_cfg.games_per_iter)
+        if total_games <= 0:
+            return []
+        # Split games across workers as evenly as possible.
+        effective_workers = min(num_workers, total_games)
+        base = total_games // effective_workers
+        remainder = total_games % effective_workers
+        per_worker = [base + (1 if i < remainder else 0) for i in range(effective_workers)]
+        # Move network state dict to CPU for cross-process transfer.
+        cpu_state = {
+            name: tensor.detach().cpu() for name, tensor in self.network.state_dict().items()
+        }
+        config_dict = self.config.to_dict()
+        game_snapshot = self.game_config.to_snapshot()
+        max_steps = self.config.evaluation.max_steps
+        temperature = self.config.temperature.training
+        worker_device = str(self.config.training.worker_device)
+        batches: list[SelfPlayWorkerBatch] = []
+        for worker_index in range(effective_workers):
+            seed = self.rng.randrange(2**31)
+            batches.append(
+                SelfPlayWorkerBatch(
+                    worker_index=worker_index,
+                    games_for_worker=per_worker[worker_index],
+                    base_seed=seed,
+                    config=config_dict,
+                    game_config=game_snapshot,
+                    network_state=cpu_state,
+                    temperature=temperature,
+                    max_steps=max_steps,
+                    device=worker_device,
+                )
+            )
+        samples: list[ReplaySample] = []
+        ctx = mp.get_context("spawn")
+        print(
+            f"  spawning {effective_workers} workers for {total_games} games "
+            f"(per_worker={per_worker})...",
+            flush=True,
+        )
+        spawn_started = time.perf_counter()
+        with ProcessPoolExecutor(max_workers=effective_workers, mp_context=ctx) as executor:
+            futures = [executor.submit(run_self_play_worker, batch) for batch in batches]
+            print(
+                f"  workers submitted in {time.perf_counter() - spawn_started:.1f}s, waiting for results...",
+                flush=True,
+            )
+            results = []
+            for future in futures:
+                res = future.result()
+                results.append(res)
+                print(
+                    f"  worker {res.worker_index} done ({len(res.samples)} samples, "
+                    f"elapsed {time.perf_counter() - spawn_started:.1f}s)",
+                    flush=True,
+                )
+        for result in sorted(results, key=lambda item: item.worker_index):
+            samples.extend(result.samples)
+        return samples
+
     def _train_batch(self, batch: list[ReplaySample]) -> tuple[float, float, float]:
         self.network.train()
         info = torch.as_tensor(
@@ -179,7 +259,8 @@ class IsMctsTrainer:
         logits, value_pred = self.network(info, legal)
         log_probs = torch.log_softmax(logits, dim=-1)
         policy_loss = -(pi * log_probs).sum(dim=-1).mean()
-        value_loss = nn.functional.mse_loss(value_pred, value_target)
+        v_scale = float(self.network.value_scale)
+        value_loss = nn.functional.mse_loss(value_pred / v_scale, value_target / v_scale)
         loss = policy_loss + value_loss
         self.optimizer.zero_grad(set_to_none=True)
         loss.backward()
@@ -204,22 +285,52 @@ class IsMctsTrainer:
             return {}
         self.network.eval()
         results: dict[str, float | int] = {}
-        logits_view = AlphaZeroLogitsView(self.network)
         for opponent in opponents:
-            result = evaluate_strategy_network(
-                logits_view,
-                self.game_config,
-                games=self.config.evaluation.games,
-                seed=self.config.run.seed + iteration * 1000,
-                opponent=opponent,
-                device=self.device,
-                encoding=self.config.encoding,
-                max_steps=self.config.evaluation.max_steps,
-                batch_size=self.config.evaluation.batch_size,
-            )
+            print(f"  eval vs {opponent}...", flush=True)
+            opp_started = time.perf_counter()
+            if self.config.mcts.eval_with_mcts:
+                eval_mcts_cfg = self.config.mcts.model_copy()
+                if self.config.mcts.eval_n_simulations > 0:
+                    eval_mcts_cfg = eval_mcts_cfg.model_copy(
+                        update={"n_simulations": self.config.mcts.eval_n_simulations}
+                    )
+                result = evaluate_with_mcts(
+                    self.network,
+                    self.game_config,
+                    eval_mcts_cfg,
+                    games=self.config.evaluation.games,
+                    seed=self.config.run.seed + iteration * 1000,
+                    opponent=opponent,
+                    device=self.device,
+                    encoding=self.config.encoding,
+                    max_steps=self.config.evaluation.max_steps,
+                    config=self.config,
+                    num_workers=self.config.training.num_workers,
+                )
+            else:
+                logits_view = AlphaZeroLogitsView(self.network)
+                result = evaluate_strategy_network(
+                    logits_view,
+                    self.game_config,
+                    games=self.config.evaluation.games,
+                    seed=self.config.run.seed + iteration * 1000,
+                    opponent=opponent,
+                    device=self.device,
+                    encoding=self.config.encoding,
+                    max_steps=self.config.evaluation.max_steps,
+                    batch_size=self.config.evaluation.batch_size,
+                )
             key = opponent.replace("-", "_")
             for metric_key, value in result.items():
                 results[f"eval/{key}/{metric_key}"] = value
+            par = result.get("play_action_rate", 0.0)
+            sd = result.get("avg_score_diff0", 0.0)
+            wr = result.get("win_rate0", 0.0)
+            print(
+                f"  eval vs {opponent} done in {time.perf_counter() - opp_started:.1f}s "
+                f"PA={par:.2f} W={wr:.2f} S={sd:.1f}",
+                flush=True,
+            )
         return results
 
     def _compute_mcts_metrics(self, samples: list[ReplaySample]) -> dict[str, float]:

src/coolrl_lost_cities/games/classic/ismcts/workers.py

@@ -0,0 +1,104 @@
+"""Multi-process self-play workers for ISMCTS.
+
+Mirrors the Deep CFR pattern: a ``ProcessPoolExecutor`` (spawn context)
+runs N worker processes, each receiving the current network state dict and
+a slice of the iteration's self-play games. Workers run network inference
+on CPU by default (small policy/value MLP, GPU contention is the bottleneck
+when sharing a single device across many workers).
+"""
+
+from __future__ import annotations
+
+import os
+import random
+from dataclasses import dataclass
+from typing import Any
+
+import torch
+
+from coolrl_lost_cities.games.classic.deep_cfr.encoding import input_dim
+from coolrl_lost_cities.games.classic.game import GameState, LostCitiesConfig
+
+from .config import IsMctsConfig, config_from_dict
+from .interleaved_self_play import play_self_play_iteration
+from .network import AlphaZeroNet
+from .replay_buffer import ReplaySample
+
+_TORCH_THREADS_CONFIGURED = False
+
+
+def _configure_worker_torch_threads() -> None:
+    global _TORCH_THREADS_CONFIGURED
+    if _TORCH_THREADS_CONFIGURED:
+        return
+    os.environ.setdefault("OMP_NUM_THREADS", "1")
+    os.environ.setdefault("MKL_NUM_THREADS", "1")
+    torch.set_num_threads(1)
+    if hasattr(torch, "set_num_interop_threads"):
+        try:
+            torch.set_num_interop_threads(1)
+        except RuntimeError:
+            pass
+    _TORCH_THREADS_CONFIGURED = True
+
+
+@dataclass(frozen=True)
+class SelfPlayWorkerBatch:
+    worker_index: int
+    games_for_worker: int
+    base_seed: int
+    config: dict[str, Any]
+    game_config: dict[str, Any]
+    network_state: dict[str, Any]
+    temperature: float
+    max_steps: int
+    device: str
+
+
+@dataclass
+class SelfPlayWorkerResult:
+    worker_index: int
+    samples: list[ReplaySample]
+
+
+def run_self_play_worker(batch: SelfPlayWorkerBatch) -> SelfPlayWorkerResult:
+    import time as _time
+
+    _t0 = _time.perf_counter()
+    print(f"  [worker {batch.worker_index}] starting ({batch.games_for_worker} games)", flush=True)
+    _configure_worker_torch_threads()
+    cfg: IsMctsConfig = config_from_dict(batch.config)
+    game_config = LostCitiesConfig(**batch.game_config)
+    device = torch.device(batch.device)
+    probe = GameState.new_game(game_config, seed=batch.base_seed)
+    in_dim = input_dim(probe, cfg.encoding)
+    action_size = probe.action_size
+    network = AlphaZeroNet.from_config(in_dim, action_size, cfg).to(device)
+    network.load_state_dict(batch.network_state)
+    network.eval()
+    print(
+        f"  [worker {batch.worker_index}] init done in {_time.perf_counter() - _t0:.1f}s, self-play start",
+        flush=True,
+    )
+    # Build a per-worker TrainingConfig with the worker's game count.
+    worker_training = cfg.training.model_copy(
+        update={"games_per_iter": int(batch.games_for_worker)}
+    )
+    rng = random.Random(batch.base_seed)
+    _sp_t0 = _time.perf_counter()
+    samples = play_self_play_iteration(
+        network,
+        cfg.mcts,
+        worker_training,
+        game_config,
+        rng,
+        device=device,
+        encoding=cfg.encoding,
+        temperature=batch.temperature,
+        max_steps=batch.max_steps,
+    )
+    print(
+        f"  [worker {batch.worker_index}] self-play done in {_time.perf_counter() - _sp_t0:.1f}s ({len(samples)} samples)",
+        flush=True,
+    )
+    return SelfPlayWorkerResult(worker_index=batch.worker_index, samples=samples)

tests/games/classic/ismcts/test_ismcts.py

@@ -1,22 +1,55 @@
 from __future__ import annotations
 
+import importlib.util
 import random
+import sys
+from pathlib import Path
 
 import numpy as np
 import torch
 from coolrl_lost_cities.games.classic.deep_cfr.encoding import encode_info_state, input_dim
 from coolrl_lost_cities.games.classic.game import GameState, LostCitiesConfig
 
+from coolrl_lost_cities.games.classic.bots.heuristic import HeuristicBot
+from coolrl_lost_cities.games.classic.bots.heuristic_py import (
+    HeuristicBot as PythonHeuristicBot,
+)
 from coolrl_lost_cities.games.classic.ismcts.config import IsMctsConfig, MctsConfig
 from coolrl_lost_cities.games.classic.ismcts.determinization import sample_determinization
 from coolrl_lost_cities.games.classic.ismcts.info_set import canonical_info_set_key
-from coolrl_lost_cities.games.classic.ismcts.mcts import IsMctsSearcher
+from coolrl_lost_cities.games.classic.ismcts.interleaved_self_play import (
+    play_self_play_iteration,
+)
+from coolrl_lost_cities.games.classic.ismcts.mcts import IsMctsSearcher, MctsNode
 from coolrl_lost_cities.games.classic.ismcts.network import AlphaZeroLogitsView, AlphaZeroNet
 from coolrl_lost_cities.games.classic.ismcts.replay_buffer import ReplayBuffer, ReplaySample
 from coolrl_lost_cities.games.classic.ismcts.self_play import play_self_play_game
 from coolrl_lost_cities.games.classic.ismcts.trainer import IsMctsTrainer
 
 
+def _python_mcts_searcher():
+    module_name = "coolrl_lost_cities.games.classic.ismcts._mcts_python_baseline"
+    existing = sys.modules.get(module_name)
+    if existing is not None:
+        return existing.IsMctsSearcher
+    path = (
+        Path(__file__).parents[4]
+        / "src"
+        / "coolrl_lost_cities"
+        / "games"
+        / "classic"
+        / "ismcts"
+        / "mcts.py"
+    )
+    spec = importlib.util.spec_from_file_location(module_name, path)
+    assert spec is not None
+    assert spec.loader is not None
+    module = importlib.util.module_from_spec(spec)
+    sys.modules[module_name] = module
+    spec.loader.exec_module(module)
+    return module.IsMctsSearcher
+
+
 def mini_config(seed: int = 1) -> LostCitiesConfig:
     return LostCitiesConfig(
         n_colors=3,
@@ -97,6 +130,143 @@ def test_mcts_prior_drives_visits() -> None:
     assert visits[favored] == max(visits.values())
 
 
+def test_search_correctness_vs_sequential() -> None:
+    for n_sims in (8, 16, 64):
+        state = GameState.new_game(mini_config(), seed=17)
+        dim = input_dim(state)
+        net = AlphaZeroNet(dim, state.action_size, hidden_size=8, num_layers=1)
+        config = MctsConfig(
+            n_simulations=n_sims,
+            parallel_simulations=1,
+            use_rollout_value=False,
+        )
+        left = IsMctsSearcher(net, config, rng=random.Random(18))
+        right = IsMctsSearcher(net, config, rng=random.Random(18))
+        assert left.search(state, state.current_player) == right.search(state, state.current_player)
+
+
+def test_cython_sequential_matches_python_sequential_visit_counts() -> None:
+    PythonIsMctsSearcher = _python_mcts_searcher()
+    for n_sims in (8, 32, 128):
+        state = GameState.new_game(mini_config(), seed=23)
+        dim = input_dim(state)
+        torch.manual_seed(24)
+        net = AlphaZeroNet(dim, state.action_size, hidden_size=8, num_layers=1)
+        config = MctsConfig(
+            n_simulations=n_sims,
+            parallel_simulations=1,
+            use_rollout_value=False,
+        )
+        python_searcher = PythonIsMctsSearcher(net, config, rng=random.Random(25))
+        cython_searcher = IsMctsSearcher(net, config, rng=random.Random(25))
+
+        assert cython_searcher.search(state, state.current_player) == python_searcher.search(
+            state, state.current_player
+        )
+
+
+def test_search_visit_counts_match_with_parallel_simulations() -> None:
+    for n_sims in (8, 32, 128):
+        state = GameState.new_game(mini_config(), seed=26)
+        dim = input_dim(state)
+        torch.manual_seed(27)
+        net = AlphaZeroNet(dim, state.action_size, hidden_size=8, num_layers=1)
+        sequential = IsMctsSearcher(
+            net,
+            MctsConfig(n_simulations=n_sims, parallel_simulations=1, use_rollout_value=False),
+            rng=random.Random(28),
+        )
+        batched = IsMctsSearcher(
+            net,
+            MctsConfig(n_simulations=n_sims, parallel_simulations=8, use_rollout_value=False),
+            rng=random.Random(28),
+        )
+
+        assert batched.search(state, state.current_player) == sequential.search(
+            state, state.current_player
+        )
+
+
+def test_search_with_virtual_loss_diversity() -> None:
+    state = GameState.new_game(mini_config(), seed=19)
+    dim = input_dim(state)
+    net = AlphaZeroNet(dim, state.action_size, hidden_size=8, num_layers=0)
+    for param in net.parameters():
+        param.data.zero_()
+    searcher = IsMctsSearcher(
+        net,
+        MctsConfig(n_simulations=64, parallel_simulations=4, virtual_loss_value=1.0),
+        rng=random.Random(20),
+    )
+    first = searcher.prepare_simulation_batch(state, state.current_player, 1)
+    searcher.evaluate_and_backup(first)
+
+    pending = searcher.prepare_simulation_batch(state, state.current_player, 4)
+    first_actions = [item.path[0].action for item in pending if item.path]
+    assert len(set(first_actions)) >= 2
+
+
+def test_heuristic_cython_fast_path_matches_python_for_random_states() -> None:
+    configs = [mini_config(seed=31), LostCitiesConfig(seed=32)]
+    py_bot = PythonHeuristicBot()
+    cy_bot = HeuristicBot()
+
+    for config in configs:
+        rng = random.Random(33)
+        checked = 0
+        attempts = 0
+        while checked < 100 and attempts < 1000:
+            attempts += 1
+            state = GameState.new_game(config, seed=rng.randrange(2**31))
+            for _ in range(rng.randrange(40)):
+                if state.terminal:
+                    break
+                legal = state.unified_legal_actions()
+                if not legal:
+                    break
+                state.apply_unified_action(rng.choice(legal))
+            if state.terminal or not state.unified_legal_actions():
+                continue
+
+            assert cy_bot.act_cython(state) == py_bot.act(state)
+            checked += 1
+
+        assert checked == 100
+
+
+def test_game_state_push_pop_unified_round_trip_snapshot() -> None:
+    rng = random.Random(34)
+    for config in (mini_config(seed=35), LostCitiesConfig(seed=36)):
+        state = GameState.new_game(config, seed=37)
+        for _ in range(100):
+            if state.terminal:
+                break
+            before = state.to_snapshot()
+            unified = rng.choice(state.unified_legal_actions())
+            local = state.from_unified_action(unified)
+            state.push_action(local)
+            state.pop_action()
+            assert state.to_snapshot() == before
+            state.apply_unified_action(unified)
+
+
+def test_mcts_node_c_array_maps_are_dict_like() -> None:
+    node = MctsNode(b"root", player=0, action_size=16)
+    node.priors[3] = 0.25
+    node.visits.setdefault(3, 0)
+    node.value_sum[3] = 1.5
+    node.virtual_visits[3] = 2
+    node.visits[3] = node.visits.get(3, 0) + 4
+
+    assert bool(node.priors)
+    assert node.priors.get(3, 0.0) == 0.25
+    assert node.visits.get(3, 0) == 4
+    assert node.value_sum[3] == 1.5
+    assert node.virtual_visits[3] == 2
+    assert 3 in node.visits
+    assert dict(node.visits.items()) == {3: 4}
+
+
 def test_replay_buffer_capacity_and_sample() -> None:
     sample = ReplaySample(
         info_state=np.zeros(4, dtype=np.float32),
@@ -127,6 +297,29 @@ def test_self_play_game_returns_signed_targets() -> None:
     assert all(sample.prior is not None for sample in samples)
 
 
+def test_interleaved_self_play_yields_complete_games() -> None:
+    config = mini_config()
+    state = GameState.new_game(config, seed=21)
+    net = AlphaZeroNet(input_dim(state), state.action_size, hidden_size=8, num_layers=1)
+    ismcts_config = IsMctsConfig.model_validate(
+        {
+            "mcts": {"n_simulations": 2, "parallel_simulations": 2},
+            "training": {"games_per_iter": 4, "interleave_games": 4, "interleave_max_batch": 16},
+        }
+    )
+    samples = play_self_play_iteration(
+        net,
+        ismcts_config.mcts,
+        ismcts_config.training,
+        config,
+        random.Random(22),
+        max_steps=80,
+    )
+    assert samples
+    assert {sample.game_index for sample in samples} == {0, 1, 2, 3}
+    assert all(np.isfinite(sample.v_target) for sample in samples)
+
+
 def test_trainer_one_iteration_smoke(tmp_path) -> None:
     config = IsMctsConfig.model_validate(
         {
@@ -185,9 +378,9 @@ def test_trainer_emits_full_eval_metrics(tmp_path) -> None:
         run_dir=tmp_path,
     )
     metrics = trainer.train()[0].to_dict()
-    assert "eval/random/avg_opened_colors" in metrics
-    assert "eval/random/bad_open_rate" in metrics
-    assert "eval/random/per_game_negative_expeditions" in metrics
+    assert "eval/random/avg_score_diff0" in metrics
+    assert "eval/random/play_action_rate" in metrics
+    assert "eval/random/win_rate0" in metrics
 
 
 def test_trainer_emits_mcts_metrics(tmp_path) -> None:
@@ -221,3 +414,39 @@ def test_trainer_emits_mcts_metrics(tmp_path) -> None:
     ):
         assert key in metrics
         assert np.isfinite(metrics[key])
+
+
+def test_smoke_iter_with_batching(tmp_path) -> None:
+    config = IsMctsConfig.model_validate(
+        {
+            "run": {"max_iterations": 1, "seed": 14, "device": "cpu"},
+            "rules": {
+                "n_colors": 3,
+                "n_ranks": 5,
+                "n_handshakes": 1,
+                "hand_size": 4,
+                "bonus_threshold": 4,
+            },
+            "network": {"hidden_size": 16, "num_layers": 1},
+            "mcts": {"n_simulations": 4, "parallel_simulations": 4},
+            "training": {
+                "games_per_iter": 1,
+                "gradient_steps_per_iter": 1,
+                "batch_size": 8,
+                "interleave_games": 4,
+                "interleave_max_batch": 16,
+            },
+            "checkpoint": {"save_every": 0},
+            "evaluation": {"eval_every": 0, "num_workers": 1, "max_steps": 80},
+        }
+    )
+    trainer = IsMctsTrainer(
+        config,
+        config.rules.to_lost_cities_config(seed=config.run.seed),
+        run_dir=tmp_path,
+    )
+    metrics = trainer.train()[0].to_dict()
+    assert metrics["samples/added"] > 0
+    assert "mcts/avg_visit_entropy" in metrics
+    assert "mcts/value_prediction_error" in metrics
+    assert "mcts/policy_mcts_kl" in metrics