From 9a27b78845c0d7c5a46c1a270da9af6dde3b3784 Mon Sep 17 00:00:00 2001
From: Marc Lanctot <lanctot@google.com>
Date: Mon, 20 Sep 2021 07:19:39 -0600
Subject: [PATCH] Remove State::UndoAction from catch and cliff_walking.
 Properly implementing this function requires significant changes to the
 implementation (extra nontrivial book-keeping).

PiperOrigin-RevId: 397732772
Change-Id: I7f5b5d4d1bcb94cf39e7f2b699f2b21259f6b0a9
---
 open_spiel/games/catch.cc              | 16 ----------------
 open_spiel/games/catch.h               |  1 -
 open_spiel/games/catch_test.cc         |  1 -
 open_spiel/games/cliff_walking.cc      | 24 ------------------------
 open_spiel/games/cliff_walking.h       |  1 -
 open_spiel/games/cliff_walking_test.cc |  1 -
 6 files changed, 44 deletions(-)

diff --git a/open_spiel/games/catch.cc b/open_spiel/games/catch.cc
index 8333496e47..0b1d41a1d2 100644
--- a/open_spiel/games/catch.cc
+++ b/open_spiel/games/catch.cc
@@ -165,22 +165,6 @@ void CatchState::ObservationTensor(Player player,
   }
 }
 
-void CatchState::UndoAction(Player player, Action move) {
-  history_.pop_back();
-  --move_number_;
-  if (player == kChancePlayerId) {
-    initialized_ = false;
-    ball_row_ = -1;
-    ball_col_ = -1;
-    paddle_col_ = -1;
-  } else {
-    int direction = move - 1;
-    paddle_col_ =
-        std::min(std::max(paddle_col_ - direction, 0), num_columns_ - 1);
-    --ball_row_;
-  }
-}
-
 std::unique_ptr<State> CatchState::Clone() const {
   return std::unique_ptr<State>(new CatchState(*this));
 }
diff --git a/open_spiel/games/catch.h b/open_spiel/games/catch.h
index aff53c75b5..e68ee55cd6 100644
--- a/open_spiel/games/catch.h
+++ b/open_spiel/games/catch.h
@@ -73,7 +73,6 @@ class CatchState : public State {
   void ObservationTensor(Player player,
                          absl::Span<float> values) const override;
   std::unique_ptr<State> Clone() const override;
-  void UndoAction(Player player, Action move) override;
   std::vector<Action> LegalActions() const override;
   ActionsAndProbs ChanceOutcomes() const override;
   CellState BoardAt(int row, int column) const;
diff --git a/open_spiel/games/catch_test.cc b/open_spiel/games/catch_test.cc
index 6f4daea13b..5fe7c87db0 100644
--- a/open_spiel/games/catch_test.cc
+++ b/open_spiel/games/catch_test.cc
@@ -29,7 +29,6 @@ void BasicCatchTests() {
   testing::LoadGameTest("catch");
   testing::ChanceOutcomesTest(*LoadGame("catch"));
   testing::RandomSimTest(*LoadGame("catch"), 100);
-  testing::RandomSimTestWithUndo(*LoadGame("catch"), 1);
 }
 
 void GetAllStatesTest() {
diff --git a/open_spiel/games/cliff_walking.cc b/open_spiel/games/cliff_walking.cc
index 9d43f3f222..416af367b3 100644
--- a/open_spiel/games/cliff_walking.cc
+++ b/open_spiel/games/cliff_walking.cc
@@ -157,30 +157,6 @@ void CliffWalkingState::InformationStateTensor(Player player,
   }
 }
 
-void CliffWalkingState::UndoAction(Player player, Action move) {
-  switch (move) {
-    case RIGHT:
-      --player_col_;
-      break;
-    case UP:
-      ++player_row_;
-      break;
-    case LEFT:
-      ++player_col_;
-      break;
-    case DOWN:
-      --player_row_;
-      break;
-    default:
-      SpielFatalError("Unexpected action");
-  }
-  player_row_ = std::min(std::max(player_row_, 0), height_ - 1);
-  player_col_ = std::min(std::max(player_col_, 0), width_ - 1);
-  --time_counter_;
-  history_.pop_back();
-  --move_number_;
-}
-
 std::unique_ptr<State> CliffWalkingState::Clone() const {
   return std::unique_ptr<State>(new CliffWalkingState(*this));
 }
diff --git a/open_spiel/games/cliff_walking.h b/open_spiel/games/cliff_walking.h
index b661a1d4ff..2a2123b3d4 100644
--- a/open_spiel/games/cliff_walking.h
+++ b/open_spiel/games/cliff_walking.h
@@ -92,7 +92,6 @@ class CliffWalkingState : public State {
   void InformationStateTensor(Player player,
                               absl::Span<float> values) const override;
   std::unique_ptr<State> Clone() const override;
-  void UndoAction(Player player, Action move) override;
   std::vector<Action> LegalActions() const override;
 
  protected:
diff --git a/open_spiel/games/cliff_walking_test.cc b/open_spiel/games/cliff_walking_test.cc
index 8d5fc6b144..caa96f7c5f 100644
--- a/open_spiel/games/cliff_walking_test.cc
+++ b/open_spiel/games/cliff_walking_test.cc
@@ -28,7 +28,6 @@ void BasicCliffWalkingTests() {
   testing::LoadGameTest("cliff_walking");
   testing::NoChanceOutcomesTest(*LoadGame("cliff_walking"));
   testing::RandomSimTest(*LoadGame("cliff_walking"), 100);
-  testing::RandomSimTestWithUndo(*LoadGame("cliff_walking"), 1);
 }
 
 }  // namespace