Refactors state_distribution.cc to remove special-casing for Universa…

…l Poker.

PiperOrigin-RevId: 287336222
Change-Id: I13d43fdf30520052050894cb0247f1156fc20a0d

open_spiel/algorithms/state_distribution.cc

@@ -24,7 +24,6 @@
 
 #include "open_spiel/abseil-cpp/absl/algorithm/container.h"
 #include "open_spiel/abseil-cpp/absl/strings/str_cat.h"
-#include "open_spiel/games/universal_poker.h"
 #include "open_spiel/simultaneous_move_game.h"
 #include "open_spiel/spiel.h"
 
@@ -153,13 +152,12 @@ HistoryDistribution UpdateIncrementalStateDistribution(
     const State& state, const Policy* opponent_policy, int player_id,
     const HistoryDistribution& previous) {
   if (previous.first.empty()) {
-    // We have a special case here as universal_poker can be very big.
-    if (state.GetGame()->GetType().short_name == "universal_poker" &&
-        state.GetGame()->NumPlayers() == 2) {
-      auto up_state =
-          dynamic_cast<const universal_poker::UniversalPokerState*>(&state);
-      return up_state->GetHistoriesConsistentWithInfostate();
-    }
+    HistoryDistribution dist = state.GetHistoriesConsistentWithInfostate();
+
+    // If the game didn't implement GetHistoriesConsistentWithInfostate, then
+    // this is empty, otherwise, we're good.
+    if (!dist.first.empty()) return dist;
+
     // If the previous pair is empty, then we have to do a BFS to find all
     // relevant nodes:
     return GetStateDistribution(state, opponent_policy);

open_spiel/algorithms/state_distribution.h

@@ -23,9 +23,6 @@
 namespace open_spiel {
 namespace algorithms {
 
-using HistoryDistribution =
-    std::pair<std::vector<std::unique_ptr<State>>, std::vector<double>>;
-
 // Returns a distribution over states at the information state containing the
 // specified state given the opponents' policies. That is, it returns
 // Pr(h | s, \pi_{-i}) by normalizing the opponents' reach probabilities over

open_spiel/games/universal_poker.cc

@@ -494,7 +494,8 @@ double UniversalPokerState::GetTotalReward(Player player) const {
 HistoryDistribution UniversalPokerState::GetHistoriesConsistentWithInfostate()
     const {
   // This is only implemented for 2 players.
-  SPIEL_CHECK_EQ(acpc_game_->GetNbPlayers(), 2);
+  if (acpc_game_->GetNbPlayers() != 2) return {};
+
   logic::CardSet is_cards;
   const logic::CardSet &our_cards = hole_cards_[cur_player_];
   for (uint8_t card : our_cards.ToCardArray()) is_cards.AddCard(card);

open_spiel/games/universal_poker.h

@@ -34,11 +34,6 @@
 namespace open_spiel {
 namespace universal_poker {
 
-// We alias this here as we can't import state_distribution.h or we'd have a
-// circular dependency.
-using HistoryDistribution =
-    std::pair<std::vector<std::unique_ptr<State>>, std::vector<double>>;
-
 class UniversalPokerGame;
 
 constexpr uint8_t kMaxUniversalPokerPlayers = 10;
@@ -72,7 +67,7 @@ class UniversalPokerState : public State {
   std::vector<Action> LegalActions() const override;
 
   // Used to make UpdateIncrementalStateDistribution much faster.
-  HistoryDistribution GetHistoriesConsistentWithInfostate() const;
+  HistoryDistribution GetHistoriesConsistentWithInfostate() const override;
 
  protected:
   void DoApplyAction(Action action_id) override;

open_spiel/spiel.h

@@ -521,6 +521,14 @@ class State {
     SpielFatalError("ResampleFromInfostate() not implemented.");
   }
 
+  // Returns a vector of states & probabilities that are consistent with the
+  // infostate from the view of the current player. By default, this is not
+  // implemented and returns an empty list.
+  virtual std::pair<std::vector<std::unique_ptr<State>>, std::vector<double>>
+  GetHistoriesConsistentWithInfostate() const {
+    return {};
+  }
+
  protected:
   // See ApplyAction.
   virtual void DoApplyAction(Action action_id) {
@@ -782,6 +790,11 @@ std::string SerializeGameAndState(const Game& game, const State& state);
 std::pair<std::shared_ptr<const Game>, std::unique_ptr<State>>
 DeserializeGameAndState(const std::string& serialized_state);
 
+// We alias this here as we can't import state_distribution.h or we'd have a
+// circular dependency.
+using HistoryDistribution =
+    std::pair<std::vector<std::unique_ptr<State>>, std::vector<double>>;
+
 }  // namespace open_spiel
 
 #endif  // THIRD_PARTY_OPEN_SPIEL_SPIEL_H_