Deep CFR regret fallback audit metrics 추가

docs/deep-cfr-regret-fallback-audit-2026-05-07.md

@@ -0,0 +1,103 @@
+# Deep CFR Regret Fallback Audit, 2026-05-07
+
+Goal: test whether all-negative regret matching fallback is a plausible source of
+early over-opening in Lost Cities Deep CFR.
+
+## Code Changes
+
+- Added traversal audit metrics for regret matching fallback decisions.
+- Default behavior remains unchanged: `regret_matching.all_negative_fallback: uniform`.
+- Added optional fallback mode: `argmax_tiebreak`.
+- Added CLI override: `--regret-fallback uniform|argmax_tiebreak`.
+
+Key metrics:
+
+- `traversal_regret_matching_decisions`
+- `traversal_regret_fallback_count`
+- `traversal_regret_fallback_rate`
+- `traversal_regret_fallback_avg_depth`
+- `traversal_regret_fallback_depth_bucket_<range>`
+- `traversal_regret_fallback_opened_colors_count_<n>`
+- `traversal_regret_fallback_action_open_new`
+- `traversal_regret_fallback_open_new_selected`
+- `traversal_regret_fallback_open_new_selected_rate`
+- `traversal_regret_fallback_legal_actions_mean`
+- `traversal_regret_fallback_legal_open_new_mean`
+- `traversal_regret_fallback_legal_discard_mean`
+- `traversal_regret_fallback_legal_draw_deck_mean`
+- `traversal_regret_fallback_legal_draw_pile_mean`
+- `traversal_regret_fallback_open_new_available_rate`
+- `traversal_regret_fallback_open_new_selection_over_availability`
+- `traversal_regret_fallback_avg_opened_colors_before_action`
+- `traversal_regret_fallback_argmax_tie_rate`
+- `traversal_regret_fallback_argmax_tie_size_mean`
+- `traversal_regret_fallback_argmax_full_tie_rate`
+- `traversal_regret_fallback_open_new_available_color_<color>`
+- `traversal_regret_fallback_open_new_selected_color_<color>`
+
+Implementation note: fallback policy state is captured immediately after the
+network policy is computed. This avoids child recursion overwriting the
+traversal-level fallback flag before the decision is recorded.
+
+## Runs
+
+Baseline long run, analyzed after it had reached iteration 210:
+
+- `runs/deep_cfr/2026-05-07_legacy_align_full_depth_slot_playability`
+
+Short comparison runs:
+
+- `runs/deep_cfr/2026-05-07_regret_fallback_uniform_20iter`
+- `runs/deep_cfr/2026-05-07_regret_fallback_argmax_tiebreak_20iter`
+
+Both short runs used the same base config and seed:
+
+- `configs/deep_cfr/deep_cfr_selfplay_full_depth_slot_playability.yaml`
+- `seed: 79`
+- `iterations: 20`
+- `save_latest_only`
+
+The 20-iteration runs below were collected before the expanded fallback timing,
+legal-action composition, and tie diagnostics were added. They should be treated
+as the first historical audit snapshot. New paired runs are needed to compare
+the expanded metrics.
+
+Instrumentation smoke run:
+
+- `runs/deep_cfr/2026-05-07_regret_fallback_metrics_smoke_1iter_v2`
+
+This run confirms the expanded metrics are emitted to `metrics.jsonl`.
+
+## Iteration 20 Snapshot
+
+| metric | uniform | argmax_tiebreak |
+|---|---:|---:|
+| traversal_regret_matching_decisions | 39,358 | 49,296 |
+| traversal_regret_fallback_count | 18,362 | 7,588 |
+| traversal_regret_fallback_rate | 0.4665 | 0.1539 |
+| traversal_regret_fallback_open_new_selected | 641 | 164 |
+| traversal_regret_fallback_open_new_selected_rate | 0.0349 | 0.0216 |
+| traversal_regret_fallback_avg_opened_colors_before_action | 4.4325 | 4.6118 |
+| eval_random_avg_opened_colors | 2.48 | 2.16 |
+| eval_random_5_color_open_count | 49 | 35 |
+| eval_safe_heuristic_avg_opened_colors | 2.50 | 2.44 |
+| eval_safe_heuristic_5_color_open_count | 50 | 44 |
+| eval_passive_discard_avg_opened_colors | 2.33 | 2.32 |
+| eval_passive_discard_5_color_open_count | 39 | 41 |
+| eval_random_avg_score_diff0 | 42.46 | 33.58 |
+| eval_safe_heuristic_avg_score_diff0 | -52.65 | -58.25 |
+
+## Read
+
+The audit confirms that uniform fallback fires frequently in the early run.
+At iteration 20, almost half of traversal regret-matching decisions use fallback
+under `uniform`.
+
+`argmax_tiebreak` sharply reduces fallback frequency and absolute fallback
+open-new selections in this 20-iteration comparison. It also lowers 5-color
+counts against random and safe heuristic opponents at iteration 20. The effect is
+not uniform across every opponent in this very short run.
+
+This is diagnostic evidence, not enough to promote `argmax_tiebreak` as the
+default. A longer 50-100 iteration paired run is still needed before deciding
+whether this fixes the plateau without hurting policy quality.

src/coolrl_lost_cities/games/classic/deep_cfr/cli.py

@@ -86,6 +86,8 @@ def _train_overrides_from_args(args: argparse.Namespace) -> dict[str, Any]:
         overrides.setdefault("evaluation", {})["eval_every"] = args.eval_every
     if args.eval_games is not None:
         overrides.setdefault("evaluation", {})["games"] = args.eval_games
+    if args.regret_fallback is not None:
+        overrides.setdefault("regret_matching", {})["all_negative_fallback"] = args.regret_fallback
     if args.no_save:
         checkpoint_overrides = overrides.setdefault("checkpoint", {})
         checkpoint_overrides["save_latest"] = False
@@ -218,6 +220,11 @@ def main(argv: list[str] | None = None) -> None:
     train.add_argument("--device")
     train.add_argument("--eval-every", type=int)
     train.add_argument("--eval-games", type=int)
+    train.add_argument(
+        "--regret-fallback",
+        choices=("uniform", "argmax_tiebreak"),
+        help="Override regret_matching.all_negative_fallback.",
+    )
     train.add_argument("--seed", type=int)
     train.add_argument("--no-save", action="store_true")
     train.add_argument("--save-latest-only", action="store_true")

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

@@ -163,6 +163,18 @@ class TraversalConfig(StrictModel):
         return max(1, int(self.worker_chunk_size))
 
 
+class RegretMatchingConfig(StrictModel):
+    all_negative_fallback: str = "uniform"
+
+    @field_validator("all_negative_fallback")
+    @classmethod
+    def _validate_all_negative_fallback(cls, value: str) -> str:
+        token = value.strip().lower()
+        if token not in {"uniform", "argmax_tiebreak"}:
+            raise ValueError("must be 'uniform' or 'argmax_tiebreak'")
+        return token
+
+
 class SelfPlayLeagueConfig(StrictModel):
     snapshot_every: int = 1
     max_snapshots: int = 20
@@ -268,6 +280,7 @@ class DeepCFRConfig(StrictModel):
     encoding: EncodingConfig = Field(default_factory=EncodingConfig)
     network: NetworkConfig = Field(default_factory=NetworkConfig)
     traversal: TraversalConfig = Field(default_factory=TraversalConfig)
+    regret_matching: RegretMatchingConfig = Field(default_factory=RegretMatchingConfig)
     self_play: SelfPlayLeagueConfig = Field(default_factory=SelfPlayLeagueConfig)
     optimization: OptimizationConfig = Field(default_factory=OptimizationConfig)
     memory: MemoryConfig = Field(default_factory=MemoryConfig)

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

@@ -294,6 +294,9 @@ class DeepCFRTrainer:
         for player, memory in enumerate(self.advantage_memories):
             self._runtime_metrics[f"advantage_player_{player}_memory_size"] = len(memory)
         self._runtime_metrics["strategy_memory_size"] = len(self.strategy_memory)
+        for key, value in total_stats.to_dict().items():
+            if key.startswith("traversal_regret_") or key == "traversal_sampled_actions":
+                self._runtime_metrics[key] = value
         return IterationMetrics(
             iteration=iteration,
             advantage_samples=self._advantage_memory_size(),
@@ -354,6 +357,7 @@ class DeepCFRTrainer:
                 cutoff_rollout_policy=self.config.traversal.cutoff_rollout_policy,
                 cutoff_rollout_max_steps=self.config.traversal.cutoff_rollout_max_steps,
                 opponent_policy=self.config.traversal.opponent_policy,
+                all_negative_fallback=self.config.regret_matching.all_negative_fallback,
                 league_advantage_networks=league_networks,
                 self_play_anchor_probability=self.config.self_play.anchor_probability,
                 self_play_current_weight=self.config.self_play.current_weight,

src/coolrl_lost_cities/games/classic/deep_cfr/traversal.pyx

@@ -88,6 +88,10 @@ cdef class CythonDeepCFRTraverser:
     cdef int cutoff_rollouts
     cdef int cutoff_rollout_max_steps
     cdef int opponent_policy_id
+    cdef int all_negative_fallback_id
+    cdef bint last_policy_regret_fallback
+    cdef int last_policy_argmax_tie_size
+    cdef bint last_policy_argmax_full_tie
     cdef float self_play_anchor_probability
     cdef float self_play_current_weight
     cdef float self_play_recent_weight
@@ -123,6 +127,7 @@ cdef class CythonDeepCFRTraverser:
         str cutoff_rollout_policy="random",
         int cutoff_rollout_max_steps=10000,
         str opponent_policy="network",
+        str all_negative_fallback="uniform",
         object league_advantage_networks=None,
         float self_play_anchor_probability=0.0,
         float self_play_current_weight=0.5,
@@ -182,6 +187,15 @@ cdef class CythonDeepCFRTraverser:
             self.opponent_policy_id = 2
         else:
             raise ValueError("opponent_policy must be 'network', 'safe_heuristic', or 'self_play_league'")
+        if all_negative_fallback == "uniform":
+            self.all_negative_fallback_id = 0
+        elif all_negative_fallback == "argmax_tiebreak":
+            self.all_negative_fallback_id = 1
+        else:
+            raise ValueError("all_negative_fallback must be 'uniform' or 'argmax_tiebreak'")
+        self.last_policy_regret_fallback = False
+        self.last_policy_argmax_tie_size = 0
+        self.last_policy_argmax_full_tie = False
         self.league_advantage_networks = [] if league_advantage_networks is None else league_advantage_networks
         self.self_play_anchor_probability = min(1.0, max(0.0, self_play_anchor_probability))
         self.self_play_current_weight = max(0.0, self_play_current_weight)
@@ -247,6 +261,9 @@ cdef class CythonDeepCFRTraverser:
         cdef float sampling_policy[MAX_ACTIONS]
         cdef unsigned char legal[MAX_ACTIONS]
         cdef object info_state
+        cdef bint policy_regret_fallback
+        cdef int policy_argmax_tie_size
+        cdef bint policy_argmax_full_tie
 
         stats.nodes += 1
         if depth > stats.max_depth_reached:
@@ -266,7 +283,7 @@ cdef class CythonDeepCFRTraverser:
             return self._cutoff_value(state, traverser, stats)
 
         player = state.current_player
-        fixed_action = self._fixed_opponent_action(state, player, traverser)
+        fixed_action = self._fixed_opponent_action(state, player, traverser, depth, stats)
         if fixed_action >= 0:
             fixed_unified_action = self._to_unified_action_c(state, fixed_action)
             swapped_deck_index = self._sample_deck_draw_chance(state, fixed_unified_action)
@@ -279,6 +296,9 @@ cdef class CythonDeepCFRTraverser:
                     state._swap_deck_cards_c(swapped_deck_index, state.deck_len - 1)
 
         info_state = self._policy(state, player, legal, policy)
+        policy_regret_fallback = self.last_policy_regret_fallback
+        policy_argmax_tie_size = self.last_policy_argmax_tie_size
+        policy_argmax_full_tie = self.last_policy_argmax_full_tie
         self._record_strategy(info_state, legal, policy, player, traverser, iteration, depth, stats)
 
         legal_count = 0
@@ -304,6 +324,16 @@ cdef class CythonDeepCFRTraverser:
                 state._swap_deck_cards_c(swapped_deck_index, state.deck_len - 1)
 
         stats.sampled_actions += 1
+        self._record_regret_matching_decision(
+            stats,
+            state,
+            player,
+            action,
+            depth,
+            policy_regret_fallback,
+            policy_argmax_tie_size,
+            policy_argmax_full_tie,
+        )
         action_prob = sampling_policy[action]
         if action_prob < self.epsilon:
             action_prob = self.epsilon
@@ -350,6 +380,12 @@ cdef class CythonDeepCFRTraverser:
         cdef int actions[MAX_ACTIONS]
         cdef int action_count
         cdef int i
+        cdef int selected
+        cdef int tie_count
+        cdef int max_tie_count
+        cdef float positive
+        cdef float positive_sum = 0.0
+        cdef float best = 0.0
 
         info_state = np.empty(self.input_dim, dtype=np.float32)
         info_view = info_state
@@ -369,7 +405,46 @@ cdef class CythonDeepCFRTraverser:
             x = torch.as_tensor(info_state, dtype=torch.float32, device=self.device).unsqueeze(0)
             advantages = networks[player](x).squeeze(0).detach().cpu().numpy().astype(np.float32)
         adv_view = advantages
+        for i in range(self.action_size):
+            if legal[i] != 0:
+                positive = adv_view[i] if adv_view[i] > 0.0 else 0.0
+                positive_sum += positive
+        self.last_policy_regret_fallback = positive_sum <= self.epsilon
+        self.last_policy_argmax_tie_size = 0
+        self.last_policy_argmax_full_tie = False
+        if not self.last_policy_regret_fallback or self.all_negative_fallback_id == 0:
+            if self.last_policy_regret_fallback:
+                max_tie_count = 0
+                for i in range(self.action_size):
+                    if legal[i] == 0:
+                        continue
+                    if max_tie_count == 0 or adv_view[i] > best:
+                        best = adv_view[i]
+                        max_tie_count = 1
+                    elif adv_view[i] == best:
+                        max_tie_count += 1
+                self.last_policy_argmax_tie_size = max_tie_count
+                self.last_policy_argmax_full_tie = max_tie_count > 1 and max_tie_count == action_count
             regret_matching_c(&adv_view[0], legal, self.action_size, self.epsilon, policy)
+        else:
+            selected = -1
+            tie_count = 0
+            for i in range(self.action_size):
+                policy[i] = 0.0
+                if legal[i] == 0:
+                    continue
+                if selected < 0 or adv_view[i] > best:
+                    selected = i
+                    best = adv_view[i]
+                    tie_count = 1
+                elif adv_view[i] == best:
+                    tie_count += 1
+                    if _next_u32(&self.rng) % <unsigned int>tie_count == 0:
+                        selected = i
+            self.last_policy_argmax_tie_size = tie_count
+            self.last_policy_argmax_full_tie = tie_count > 1 and tie_count == action_count
+            if selected >= 0:
+                policy[selected] = 1.0
         return info_state
 
     cdef void _sampling_policy(
@@ -402,7 +477,14 @@ cdef class CythonDeepCFRTraverser:
             else:
                 out_policy[i] = 0.0
 
-    cdef int _fixed_opponent_action(self, GameState state, int player, int traverser) except *:
+    cdef int _fixed_opponent_action(
+        self,
+        GameState state,
+        int player,
+        int traverser,
+        int depth,
+        object stats,
+    ) except *:
         cdef int bucket
         cdef object networks
         cdef unsigned char legal[MAX_ACTIONS]
@@ -435,8 +517,116 @@ cdef class CythonDeepCFRTraverser:
         if count <= 0:
             return -1
         unified_action = _sample_policy_from_actions_c(policy, actions, count, _next_double(&self.rng))
+        self._record_regret_matching_decision(
+            stats,
+            state,
+            player,
+            unified_action,
+            depth,
+            self.last_policy_regret_fallback,
+            self.last_policy_argmax_tie_size,
+            self.last_policy_argmax_full_tie,
+        )
         return self._from_unified_action_c(state, unified_action)
 
+    cdef void _record_regret_matching_decision(
+        self,
+        object stats,
+        GameState state,
+        int player,
+        int unified_action,
+        int depth,
+        bint fallback,
+        int argmax_tie_size,
+        bint argmax_full_tie,
+    ):
+        cdef int card_action_size = 2 * state.hand_size
+        cdef int actions[MAX_ACTIONS]
+        cdef int legal_count
+        cdef int legal_action
+        cdef int opened_colors
+        cdef int slot
+        cdef int card
+        cdef int color
+        stats.regret_matching_decisions += 1
+        if not fallback:
+            return
+        stats.regret_fallback_count += 1
+        stats.regret_fallback_depth_sum += depth
+        self._record_fallback_depth_bucket(stats, depth)
+        opened_colors = self._opened_color_count(state, player)
+        stats.regret_fallback_opened_colors_sum += opened_colors
+        stats.regret_fallback_opened_colors_buckets[opened_colors] = (
+            stats.regret_fallback_opened_colors_buckets.get(opened_colors, 0) + 1
+        )
+        if argmax_tie_size > 1:
+            stats.regret_fallback_argmax_tie_count += 1
+            stats.regret_fallback_argmax_tie_size_sum += argmax_tie_size
+        if argmax_full_tie:
+            stats.regret_fallback_argmax_full_tie_count += 1
+        legal_count = state._unified_legal_actions_c(actions)
+        stats.regret_fallback_legal_actions_sum += legal_count
+        for slot in range(legal_count):
+            legal_action = actions[slot]
+            if legal_action < card_action_size:
+                if legal_action % 2 == 1:
+                    stats.regret_fallback_legal_discard_sum += 1
+                    continue
+                card = state.hand_cards[state._hand_index(player, legal_action // 2)]
+                color = state._card_color(card)
+                if state.expedition_lens[state._expedition_len_index(player, color)] == 0:
+                    stats.regret_fallback_legal_open_new_sum += 1
+                    stats.regret_fallback_open_new_available_by_color[color] = (
+                        stats.regret_fallback_open_new_available_by_color.get(color, 0) + 1
+                    )
+                else:
+                    stats.regret_fallback_legal_play_existing_sum += 1
+                continue
+            if legal_action == card_action_size:
+                stats.regret_fallback_legal_draw_deck_sum += 1
+            else:
+                stats.regret_fallback_legal_draw_pile_sum += 1
+        if unified_action < card_action_size:
+            if unified_action % 2 == 1:
+                stats.regret_fallback_action_discard += 1
+                return
+            slot = unified_action // 2
+            card = state.hand_cards[state._hand_index(player, slot)]
+            color = state._card_color(card)
+            if state.expedition_lens[state._expedition_len_index(player, color)] == 0:
+                stats.regret_fallback_action_open_new += 1
+                stats.regret_fallback_open_new_selected_by_color[color] = (
+                    stats.regret_fallback_open_new_selected_by_color.get(color, 0) + 1
+                )
+            else:
+                stats.regret_fallback_action_play_existing += 1
+            return
+        if unified_action == card_action_size:
+            stats.regret_fallback_action_draw_deck += 1
+        else:
+            stats.regret_fallback_action_draw_pile += 1
+
+    cdef void _record_fallback_depth_bucket(self, object stats, int depth):
+        cdef int width = 50
+        cdef int max_depth = 400
+        cdef int start = (depth // width) * width
+        cdef str key
+        if start >= max_depth:
+            key = f"{max_depth}_plus"
+        else:
+            key = f"{start}_{start + width - 1}"
+        stats.regret_fallback_depth_buckets[key] = (
+            stats.regret_fallback_depth_buckets.get(key, 0) + 1
+        )
+
+    cdef int _opened_color_count(self, GameState state, int player) noexcept:
+        cdef int color
+        cdef int count = 0
+        for color in range(state.n_colors):
+            if state.expedition_lens[state._expedition_len_index(player, color)] > 0:
+                count += 1
+        return count
+
     cdef int _self_play_bucket(self) noexcept:
         cdef int recent_count
         cdef int older_count
@@ -665,6 +855,7 @@ def run_cython_traversal_batch(
     str cutoff_rollout_policy="random",
     int cutoff_rollout_max_steps=10000,
     str opponent_policy="network",
+    str all_negative_fallback="uniform",
     object league_advantage_networks=None,
     float self_play_anchor_probability=0.0,
     float self_play_current_weight=0.5,
@@ -700,6 +891,7 @@ def run_cython_traversal_batch(
         cutoff_rollout_policy=cutoff_rollout_policy,
         cutoff_rollout_max_steps=cutoff_rollout_max_steps,
         opponent_policy=opponent_policy,
+        all_negative_fallback=all_negative_fallback,
         league_advantage_networks=league_advantage_networks,
         self_play_anchor_probability=self_play_anchor_probability,
         self_play_current_weight=self_play_current_weight,

src/coolrl_lost_cities/games/classic/deep_cfr/traversal_stats.py

@@ -13,6 +13,28 @@ class TraversalStats:
     advantage_samples: int = 0
     strategy_samples: int = 0
     sampled_actions: int = 0
+    regret_matching_decisions: int = 0
+    regret_fallback_count: int = 0
+    regret_fallback_depth_sum: int = 0
+    regret_fallback_opened_colors_sum: int = 0
+    regret_fallback_legal_actions_sum: int = 0
+    regret_fallback_legal_play_existing_sum: int = 0
+    regret_fallback_legal_open_new_sum: int = 0
+    regret_fallback_legal_discard_sum: int = 0
+    regret_fallback_legal_draw_deck_sum: int = 0
+    regret_fallback_legal_draw_pile_sum: int = 0
+    regret_fallback_action_play_existing: int = 0
+    regret_fallback_action_open_new: int = 0
+    regret_fallback_action_discard: int = 0
+    regret_fallback_action_draw_deck: int = 0
+    regret_fallback_action_draw_pile: int = 0
+    regret_fallback_argmax_tie_count: int = 0
+    regret_fallback_argmax_tie_size_sum: int = 0
+    regret_fallback_argmax_full_tie_count: int = 0
+    regret_fallback_depth_buckets: dict[str, int] = field(default_factory=dict)
+    regret_fallback_opened_colors_buckets: dict[int, int] = field(default_factory=dict)
+    regret_fallback_open_new_available_by_color: dict[int, int] = field(default_factory=dict)
+    regret_fallback_open_new_selected_by_color: dict[int, int] = field(default_factory=dict)
     cutoff_rollouts: int = 0
     cutoff_rollout_steps: int = 0
     cutoff_rollout_timeouts: int = 0
@@ -28,6 +50,42 @@ class TraversalStats:
         self.advantage_samples += other.advantage_samples
         self.strategy_samples += other.strategy_samples
         self.sampled_actions += other.sampled_actions
+        self.regret_matching_decisions += other.regret_matching_decisions
+        self.regret_fallback_count += other.regret_fallback_count
+        self.regret_fallback_depth_sum += other.regret_fallback_depth_sum
+        self.regret_fallback_opened_colors_sum += other.regret_fallback_opened_colors_sum
+        self.regret_fallback_legal_actions_sum += other.regret_fallback_legal_actions_sum
+        self.regret_fallback_legal_play_existing_sum += (
+            other.regret_fallback_legal_play_existing_sum
+        )
+        self.regret_fallback_legal_open_new_sum += other.regret_fallback_legal_open_new_sum
+        self.regret_fallback_legal_discard_sum += other.regret_fallback_legal_discard_sum
+        self.regret_fallback_legal_draw_deck_sum += other.regret_fallback_legal_draw_deck_sum
+        self.regret_fallback_legal_draw_pile_sum += other.regret_fallback_legal_draw_pile_sum
+        self.regret_fallback_action_play_existing += other.regret_fallback_action_play_existing
+        self.regret_fallback_action_open_new += other.regret_fallback_action_open_new
+        self.regret_fallback_action_discard += other.regret_fallback_action_discard
+        self.regret_fallback_action_draw_deck += other.regret_fallback_action_draw_deck
+        self.regret_fallback_action_draw_pile += other.regret_fallback_action_draw_pile
+        self.regret_fallback_argmax_tie_count += other.regret_fallback_argmax_tie_count
+        self.regret_fallback_argmax_tie_size_sum += other.regret_fallback_argmax_tie_size_sum
+        self.regret_fallback_argmax_full_tie_count += other.regret_fallback_argmax_full_tie_count
+        for key, value in other.regret_fallback_depth_buckets.items():
+            self.regret_fallback_depth_buckets[key] = (
+                self.regret_fallback_depth_buckets.get(key, 0) + value
+            )
+        for key, value in other.regret_fallback_opened_colors_buckets.items():
+            self.regret_fallback_opened_colors_buckets[key] = (
+                self.regret_fallback_opened_colors_buckets.get(key, 0) + value
+            )
+        for key, value in other.regret_fallback_open_new_available_by_color.items():
+            self.regret_fallback_open_new_available_by_color[key] = (
+                self.regret_fallback_open_new_available_by_color.get(key, 0) + value
+            )
+        for key, value in other.regret_fallback_open_new_selected_by_color.items():
+            self.regret_fallback_open_new_selected_by_color[key] = (
+                self.regret_fallback_open_new_selected_by_color.get(key, 0) + value
+            )
         self.cutoff_rollouts += other.cutoff_rollouts
         self.cutoff_rollout_steps += other.cutoff_rollout_steps
         self.cutoff_rollout_timeouts += other.cutoff_rollout_timeouts
@@ -43,6 +101,73 @@ class TraversalStats:
     def avg_endpoint_depth(self) -> float:
         return self.endpoint_depth_sum / max(1, self.endpoints)
 
+    @property
+    def regret_fallback_rate(self) -> float:
+        return self.regret_fallback_count / max(1, self.regret_matching_decisions)
+
+    @property
+    def regret_fallback_open_new_selected_rate(self) -> float:
+        return self.regret_fallback_action_open_new / max(1, self.regret_fallback_count)
+
+    @property
+    def regret_fallback_avg_depth(self) -> float:
+        return self.regret_fallback_depth_sum / max(1, self.regret_fallback_count)
+
+    @property
+    def regret_fallback_avg_opened_colors_before_action(self) -> float:
+        return self.regret_fallback_opened_colors_sum / max(1, self.regret_fallback_count)
+
+    @property
+    def regret_fallback_avg_legal_actions(self) -> float:
+        return self.regret_fallback_legal_actions_sum / max(1, self.regret_fallback_count)
+
+    @property
+    def regret_fallback_avg_legal_play_existing(self) -> float:
+        return self.regret_fallback_legal_play_existing_sum / max(1, self.regret_fallback_count)
+
+    @property
+    def regret_fallback_avg_legal_open_new(self) -> float:
+        return self.regret_fallback_legal_open_new_sum / max(1, self.regret_fallback_count)
+
+    @property
+    def regret_fallback_avg_legal_discard(self) -> float:
+        return self.regret_fallback_legal_discard_sum / max(1, self.regret_fallback_count)
+
+    @property
+    def regret_fallback_avg_legal_draw_deck(self) -> float:
+        return self.regret_fallback_legal_draw_deck_sum / max(1, self.regret_fallback_count)
+
+    @property
+    def regret_fallback_avg_legal_draw_pile(self) -> float:
+        return self.regret_fallback_legal_draw_pile_sum / max(1, self.regret_fallback_count)
+
+    @property
+    def regret_fallback_open_new_available_rate(self) -> float:
+        return self.regret_fallback_legal_open_new_sum / max(
+            1, self.regret_fallback_legal_actions_sum
+        )
+
+    @property
+    def regret_fallback_open_new_selection_over_availability(self) -> float:
+        available_rate = self.regret_fallback_open_new_available_rate
+        if available_rate <= 0.0:
+            return 0.0
+        return self.regret_fallback_open_new_selected_rate / available_rate
+
+    @property
+    def regret_fallback_argmax_tie_rate(self) -> float:
+        return self.regret_fallback_argmax_tie_count / max(1, self.regret_fallback_count)
+
+    @property
+    def regret_fallback_argmax_avg_tie_size(self) -> float:
+        return self.regret_fallback_argmax_tie_size_sum / max(
+            1, self.regret_fallback_argmax_tie_count
+        )
+
+    @property
+    def regret_fallback_argmax_full_tie_rate(self) -> float:
+        return self.regret_fallback_argmax_full_tie_count / max(1, self.regret_fallback_count)
+
     def to_dict(self) -> dict[str, float | int]:
         return {
             "traversal_nodes": self.nodes,
@@ -53,6 +178,57 @@ class TraversalStats:
             "traversal_advantage_samples": self.advantage_samples,
             "traversal_strategy_samples": self.strategy_samples,
             "traversal_sampled_actions": self.sampled_actions,
+            "traversal_regret_matching_decisions": self.regret_matching_decisions,
+            "traversal_regret_fallback_count": self.regret_fallback_count,
+            "traversal_regret_fallback_rate": self.regret_fallback_rate,
+            "traversal_regret_fallback_avg_depth": self.regret_fallback_avg_depth,
+            "traversal_regret_fallback_action_play_existing": self.regret_fallback_action_play_existing,
+            "traversal_regret_fallback_action_open_new": self.regret_fallback_action_open_new,
+            "traversal_regret_fallback_action_discard": self.regret_fallback_action_discard,
+            "traversal_regret_fallback_action_draw_deck": self.regret_fallback_action_draw_deck,
+            "traversal_regret_fallback_action_draw_pile": self.regret_fallback_action_draw_pile,
+            "traversal_regret_fallback_legal_actions_mean": (
+                self.regret_fallback_avg_legal_actions
+            ),
+            "traversal_regret_fallback_legal_play_existing_mean": (
+                self.regret_fallback_avg_legal_play_existing
+            ),
+            "traversal_regret_fallback_legal_open_new_mean": (
+                self.regret_fallback_avg_legal_open_new
+            ),
+            "traversal_regret_fallback_legal_discard_mean": (
+                self.regret_fallback_avg_legal_discard
+            ),
+            "traversal_regret_fallback_legal_draw_deck_mean": (
+                self.regret_fallback_avg_legal_draw_deck
+            ),
+            "traversal_regret_fallback_legal_draw_pile_mean": (
+                self.regret_fallback_avg_legal_draw_pile
+            ),
+            "traversal_regret_fallback_open_new_available_rate": (
+                self.regret_fallback_open_new_available_rate
+            ),
+            "traversal_regret_fallback_open_new_selected": self.regret_fallback_action_open_new,
+            "traversal_regret_fallback_open_new_selected_rate": (
+                self.regret_fallback_open_new_selected_rate
+            ),
+            "traversal_regret_fallback_open_new_selection_over_availability": (
+                self.regret_fallback_open_new_selection_over_availability
+            ),
+            "traversal_regret_fallback_avg_opened_colors_before_action": (
+                self.regret_fallback_avg_opened_colors_before_action
+            ),
+            "traversal_regret_fallback_argmax_tie_count": (self.regret_fallback_argmax_tie_count),
+            "traversal_regret_fallback_argmax_tie_rate": (self.regret_fallback_argmax_tie_rate),
+            "traversal_regret_fallback_argmax_tie_size_mean": (
+                self.regret_fallback_argmax_avg_tie_size
+            ),
+            "traversal_regret_fallback_argmax_full_tie_count": (
+                self.regret_fallback_argmax_full_tie_count
+            ),
+            "traversal_regret_fallback_argmax_full_tie_rate": (
+                self.regret_fallback_argmax_full_tie_rate
+            ),
             "traversal_cutoff_rollouts": self.cutoff_rollouts,
             "traversal_cutoff_rollout_steps": self.cutoff_rollout_steps,
             "traversal_cutoff_rollout_timeouts": self.cutoff_rollout_timeouts,
@@ -63,4 +239,20 @@ class TraversalStats:
                 f"traversal_endpoint_depth_bucket_{key}": value
                 for key, value in self.endpoint_depth_buckets.items()
             },
+            **{
+                f"traversal_regret_fallback_depth_bucket_{key}": value
+                for key, value in self.regret_fallback_depth_buckets.items()
+            },
+            **{
+                f"traversal_regret_fallback_opened_colors_count_{key}": value
+                for key, value in self.regret_fallback_opened_colors_buckets.items()
+            },
+            **{
+                f"traversal_regret_fallback_open_new_available_color_{key}": value
+                for key, value in self.regret_fallback_open_new_available_by_color.items()
+            },
+            **{
+                f"traversal_regret_fallback_open_new_selected_color_{key}": value
+                for key, value in self.regret_fallback_open_new_selected_by_color.items()
+            },
         }

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

@@ -100,6 +100,7 @@ def run_traversal_worker_batch(batch: TraversalWorkerBatch) -> TraversalWorkerRe
         cutoff_rollout_policy=cfg.traversal.cutoff_rollout_policy,
         cutoff_rollout_max_steps=cfg.traversal.cutoff_rollout_max_steps,
         opponent_policy=cfg.traversal.opponent_policy,
+        all_negative_fallback=cfg.regret_matching.all_negative_fallback,
         league_advantage_networks=league_networks,
         self_play_anchor_probability=cfg.self_play.anchor_probability,
         self_play_current_weight=cfg.self_play.current_weight,

tests/games/classic/test_deep_cfr_trainer.py

@@ -64,6 +64,7 @@ def test_deep_cfr_loads_mapped_legacy_reproduction_config() -> None:
     assert config.evaluation.resolved_batch_size() == 64
     assert config.evaluation.device == "trainer"
     assert config.evaluation.resolved_num_workers() == 4
+    assert config.regret_matching.all_negative_fallback == "uniform"
     assert config.checkpoint.save_iteration_interval == 10
     assert (
         config.checkpoint.directory == "runs/deep_cfr/deep_cfr_selfplay_full_depth_slot_playability"
@@ -84,6 +85,7 @@ def test_deep_cfr_train_cli_count_overrides_disable_duration_limits() -> None:
             "checkpoint_dir": None,
             "eval_every": None,
             "eval_games": None,
+            "regret_fallback": "argmax_tiebreak",
             "no_save": True,
             "save_latest_only": False,
             "save_iteration_interval": None,
@@ -100,6 +102,7 @@ def test_deep_cfr_train_cli_count_overrides_disable_duration_limits() -> None:
     assert overridden.traversal.traversals_per_player is None
     assert overridden.traversal.resolved_traversals_per_player() == 1
     assert overridden.traversal.resolved_num_workers() == 0
+    assert overridden.regret_matching.all_negative_fallback == "argmax_tiebreak"
     assert overridden.checkpoint.save_every_iteration is False
     assert overridden.checkpoint.save_latest is False
 
@@ -118,6 +121,7 @@ def test_deep_cfr_train_cli_checkpoint_save_overrides() -> None:
             "checkpoint_dir": None,
             "eval_every": None,
             "eval_games": None,
+            "regret_fallback": None,
             "no_save": False,
             "save_latest_only": True,
             "save_iteration_interval": 1,
@@ -388,6 +392,57 @@ def test_deep_cfr_cython_traverser_supports_outcome_sampling_and_rollout_cutoffs
     assert np.all(sample.target[unsampled_legal] == 0.0)
 
 
+def test_deep_cfr_cython_traverser_records_regret_fallback_metrics() -> None:
+    trainer = DeepCFRTrainer(
+        _deep_cfr_config(
+            {
+                "run": {"iterations": 1, "seed": 37},
+                "network": {"hidden_size": 16},
+                "traversal": {"traversals_per_iteration": 1, "max_depth": 1},
+                "optimization": {"batch_size": 2},
+                "checkpoint": {"save_every_iteration": False},
+                "regret_matching": {"all_negative_fallback": "argmax_tiebreak"},
+            }
+        ),
+        LostCitiesConfig(seed=37),
+    )
+    for network in trainer.advantage_networks:
+        for parameter in network.parameters():
+            parameter.data.zero_()
+    state = GameState.new_game(LostCitiesConfig(seed=37), seed=37)
+    traverser = CythonDeepCFRTraverser(
+        trainer.advantage_networks,
+        device=trainer.device,
+        action_size=trainer.action_size,
+        max_depth=1,
+        all_negative_fallback="argmax_tiebreak",
+        seed=37,
+    )
+
+    _, stats = traverser.traverse(state, traverser=0, iteration=1)
+    metrics = stats.to_dict()
+    action_count_sum = (
+        stats.regret_fallback_action_play_existing
+        + stats.regret_fallback_action_open_new
+        + stats.regret_fallback_action_discard
+        + stats.regret_fallback_action_draw_deck
+        + stats.regret_fallback_action_draw_pile
+    )
+
+    assert stats.regret_matching_decisions > 0
+    assert stats.regret_fallback_count > 0
+    assert action_count_sum == stats.regret_fallback_count
+    assert metrics["traversal_regret_fallback_rate"] > 0.0
+    assert "traversal_regret_fallback_open_new_selected_rate" in metrics
+    assert metrics["traversal_regret_fallback_legal_actions_mean"] > 0.0
+    assert "traversal_regret_fallback_open_new_available_rate" in metrics
+    assert "traversal_regret_fallback_open_new_selection_over_availability" in metrics
+    assert "traversal_regret_fallback_depth_bucket_0_49" in metrics
+    assert "traversal_regret_fallback_opened_colors_count_0" in metrics
+    assert metrics["traversal_regret_fallback_argmax_tie_rate"] > 0.0
+    assert metrics["traversal_regret_fallback_argmax_tie_size_mean"] > 0.0
+
+
 def test_reservoir_memory_caps_samples_and_filters_player_batches() -> None:
     memory = ReservoirMemory(capacity=3)
     rng = np.random.default_rng(37)