Simplify registering a single_tensor observer for a game

PiperOrigin-RevId: 512028396 Change-Id: I581542eba9d254d70d55c42ea92ad2057a70d77f
willmcgowan · Feb 28, 2023 · edca9e1 · edca9e1
1 parent 4d674e4
commit edca9e1
Show file tree

Hide file tree

Showing 3 changed files with 29 additions and 10 deletions.
diff --git a/open_spiel/games/leduc_poker.cc b/open_spiel/games/leduc_poker.cc
@@ -74,16 +74,7 @@ std::string StatelessActionToString(Action action) {
   }
 }
 
-// Provides the observations / infostates as defined on the state
-// as a single tensor.
-std::shared_ptr<Observer> MakeSingleTensorObserver(
-    const Game& game, absl::optional<IIGObservationType> iig_obs_type,
-    const GameParameters& params) {
-  return std::shared_ptr<Observer>(game.MakeBuiltInObserver(iig_obs_type));
-}
-
-ObserverRegisterer single_tensor(
-    kGameType.short_name, "single_tensor", MakeSingleTensorObserver);
+RegisterSingleTensorObserver single_tensor(kGameType.short_name);
 }  // namespace
 
 // The Observer class is responsible for creating representations of the game

diff --git a/open_spiel/observer.cc b/open_spiel/observer.cc
@@ -339,6 +339,18 @@ void ObserverRegisterer::RegisterObserver(const std::string& game_name,
   observers()[key] = creator;
 }
 
+std::shared_ptr<Observer> MakeSingleTensorObserver(
+    const Game& game, absl::optional<IIGObservationType> iig_obs_type,
+    const GameParameters& params) {
+  return std::shared_ptr<Observer>(game.MakeBuiltInObserver(iig_obs_type));
+}
+
+RegisterSingleTensorObserver::RegisterSingleTensorObserver(
+    const std::string& game_name) {
+  ObserverRegisterer single_tensor(game_name, "single_tensor",
+                                   MakeSingleTensorObserver);
+}
+
 std::shared_ptr<Observer> ObserverRegisterer::CreateByName(
     const std::string& observer_name,
     const Game& game,

diff --git a/open_spiel/observer.h b/open_spiel/observer.h
@@ -443,6 +443,22 @@ class ObserverRegisterer {
   }
 };
 
+// Registers an observer named "single_tensor" which falls back to
+// state.observation_tensor or state.information_state_tensor (which generate a
+// single tensor).
+//
+// Note that one cannot pass empty ObservationParams to
+// game->MakeObserver(...) to achieve the same behavior in general:
+// leduc, goofspiel and many other games will generate multiple tensors in that
+// case.
+//
+// Use:
+// RegisterSingleTensorObserver single_tensor(kGameType.short_name);
+class RegisterSingleTensorObserver {
+ public:
+  RegisterSingleTensorObserver(const std::string& game_name);
+};
+
 // Pure function that creates a tensor from an observer. Slower than using an
 // Observation, but threadsafe. This is useful when you cannot keep an
 // Observation around to use multiple times.