add game: squadro

docs/games.md

@@ -75,6 +75,7 @@ Status                                       | Game
 <font color="orange"><b>~</b></font>         | [Slovenian Tarok](#slovenian-tarok)
 <font color="orange"><b>~</b></font>         | [Skat (simplified bidding)](#skat-simplified-bidding)
 <font color="orange"><b>~</b></font>         | [Solitaire (K+)](#solitaire-k)
+<font color="orange"><b>~</b></font>         | [Squadro](#squadro)
 ![](_static/green_circ10.png "green circle") | [Tic-Tac-Toe](#tic-tac-toe)
 ![](_static/green_circ10.png "green circle") | [Tiny Bridge](#tiny-bridge)
 ![](_static/green_circ10.png "green circle") | [Tiny Hanabi](#tiny-hanabi)
@@ -777,6 +778,16 @@ Status                                       | Game
 *   [Wikipedia](https://en.wikipedia.org/wiki/Klondike_\(solitaire\)) and
     [Bjarnason et al. '07, Searching solitaire in real time](http://web.engr.oregonstate.edu/~afern/papers/solitaire.pdf)
 
+### Squadro
+
+*   Each turn, players can move their one of their pieces on the board.
+*   Uses tokens on a grid.
+*   Modern game.
+*   Deterministic.
+*   Perfect information.
+*   2 players.
+*   [bgg](https://boardgamegeek.com/boardgame/245222/squadro)
+
 ### Tic-Tac-Toe
 
 *   Players place tokens to try and form a pattern.

open_spiel/games/CMakeLists.txt

@@ -157,6 +157,8 @@ set(GAME_SOURCES
   skat.h
   solitaire.cc
   solitaire.h
+  squadro.cc
+  squadro.h
   stones_and_gems.cc
   stones_and_gems.h
   tarok.cc
@@ -560,6 +562,10 @@ add_executable(solitaire_test solitaire_test.cc ${OPEN_SPIEL_OBJECTS}
                $<TARGET_OBJECTS:tests>)
 add_test(solitaire_test solitaire_test)
 
+add_executable(squadro_test squadro_test.cc ${OPEN_SPIEL_OBJECTS}
+               $<TARGET_OBJECTS:tests>)
+add_test(squadro_test squadro_test)
+
 add_executable(stones_and_gems_test stones_and_gems_test.cc
                ${OPEN_SPIEL_OBJECTS}
                $<TARGET_OBJECTS:tests>)

open_spiel/games/squadro.cc

@@ -0,0 +1,310 @@
+// Copyright 2019 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "open_spiel/games/squadro.h"
+
+#include <algorithm>
+#include <memory>
+#include <utility>
+
+#include "open_spiel/utils/tensor_view.h"
+
+namespace open_spiel {
+namespace squadro {
+namespace {
+
+// Facts about the game
+const GameType kGameType{
+    /*short_name=*/"squadro",
+    /*long_name=*/"Squadro",
+    GameType::Dynamics::kSequential,
+    GameType::ChanceMode::kDeterministic,
+    GameType::Information::kPerfectInformation,
+    GameType::Utility::kZeroSum,
+    GameType::RewardModel::kTerminal,
+    /*max_num_players=*/2,
+    /*min_num_players=*/2,
+    /*provides_information_state_string=*/true,
+    /*provides_information_state_tensor=*/false,
+    /*provides_observation_string=*/true,
+    /*provides_observation_tensor=*/true,
+    /*parameter_specification=*/{}  // no parameters
+};
+
+std::shared_ptr<const Game> Factory(const GameParameters& params) {
+  return std::shared_ptr<const Game>(new SquadroGame(params));
+}
+
+REGISTER_SPIEL_GAME(kGameType, Factory);
+
+std::string PlayerToString(Player player) {
+  switch (player) {
+    case 0:
+      return "P0";
+    case 1:
+      return "P1";
+    default:
+      SpielFatalError(absl::StrCat("Invalid player id ", player));
+  }
+}
+
+std::string CellToString(int row, int col, 
+                         const std::array<std::array<Position, kRows>, kNumPlayers>& board) {
+  if (board[0][col].position == row) {
+    if (board[0][col].direction == TokenState::forward) {
+      return "^";
+    } else if (board[0][col].direction == TokenState::backward) {
+      return "v";
+    }
+  }
+  if (board[1][row].position == col) {
+    if (board[1][row].direction == TokenState::forward) {
+      return ">";
+    } else if (board[1][row].direction == TokenState::backward) {
+      return "<";
+    }
+  }
+  return ".";
+}
+
+}  // namespace
+
+int SquadroState::CurrentPlayer() const {
+  if (IsTerminal()) {
+    return kTerminalPlayerId;
+  } else {
+    return current_player_;
+  }
+}
+
+bool SquadroState::OverpassOpponent(int opponent, int player_position, Action move) {
+  bool overpassOpponent = false;
+
+  while (board_[opponent][player_position].position == move + 1) {
+      overpassOpponent = true;
+      // Send opponent player back to default position
+      if (board_[opponent][player_position].direction == TokenState::forward) {
+        board_[opponent][player_position].position = 0;
+      } else {
+        board_[opponent][player_position].position = 6;
+      }
+      player_position += board_[current_player_][move + 1].direction == TokenState::forward ? 1 : -1;
+    }
+  board_[current_player_][move + 1].position = player_position;
+  return overpassOpponent;
+}
+
+void SquadroState::DoApplyAction(Action move) {
+  int playerPosition = board_[current_player_][move + 1].position;
+  TokenState playerDirection = board_[current_player_][move + 1].direction;
+  int steps = playerDirection == TokenState::forward ? movements_[current_player_][move].forward : movements_[current_player_][move].backward;
+  int other_player = 1 - current_player_;
+  bool overpassOpponent = false;
+  int unit_move = playerDirection == TokenState::forward ? 1 : -1;
+  int finalPosition = playerPosition + steps;
+
+  do {
+    playerPosition += unit_move;
+    board_[current_player_][move + 1].position = playerPosition;
+    overpassOpponent = OverpassOpponent(other_player, playerPosition, move);
+  } while (playerPosition > 0 && playerPosition < kRows - 1 && unit_move * playerPosition < unit_move * finalPosition && !overpassOpponent);
+
+  if (board_[current_player_][move + 1].position == 0) {
+    board_[current_player_][move + 1].direction = TokenState::missing; // Token removed from the board
+    ++missing_tokens_[current_player_];
+  } else if (board_[current_player_][move + 1].position == 6) {
+    board_[current_player_][move + 1].direction = TokenState::backward; // Invert token direction when it reaches the end of the board
+  }
+
+  if (missing_tokens_[current_player_] == 4) {
+    outcome_ = current_player_ == 0 ? Outcome::kPlayer1 : Outcome::kPlayer2;
+  }
+
+  ++moves_made_;
+  if (moves_made_ >= 200) {
+    outcome_ = Outcome::kDraw;
+  }
+
+  current_player_ = other_player;
+}
+
+std::vector<Action> SquadroState::LegalActions() const {
+  std::vector<Action> moves;
+  if (IsTerminal()) return moves;
+  for (int pos = 0; pos < kNumActions; ++pos) {
+    if (board_[current_player_][pos + 1].direction != TokenState::missing) moves.push_back(pos);
+  }
+  return moves;
+}
+
+std::string SquadroState::ActionToString(Player player,
+                                             Action action_id) const {
+  return absl::StrCat(PlayerToString(player), action_id);
+}
+
+SquadroState::SquadroState(std::shared_ptr<const Game> game)
+    : State(game) {
+      for (int player = 0; player <= 1; ++player) {
+        for (int pos = 0; pos < kRows; ++pos) {
+          if (pos == 0 || pos == 6) {
+            // There are only 5 pieces per player. No pieces are present in the corners.
+            board_[player][pos] = {0, TokenState::missing};
+          } else {
+            board_[player][pos] = {0, TokenState::forward};
+          }
+        }
+      }
+}
+
+std::string SquadroState::ToString() const {
+  std::string str;
+  for (int row = kRows - 1; row >= 0; --row) {
+    for (int col = 0; col < kCols; ++col) {
+      str.append(CellToString(row, col, board_));
+    }
+    str.append("\n");
+  }
+  str.append("C");
+  int current_player = CurrentPlayer();
+  if (current_player == kTerminalPlayerId) {
+    str.append("2");
+  } else {
+    str.append(std::to_string(CurrentPlayer()));
+  }
+  return str;
+}
+
+bool SquadroState::IsTerminal() const {
+  return outcome_ != Outcome::kUnknown;
+}
+
+std::vector<double> SquadroState::Returns() const {
+  if (outcome_ == Outcome::kPlayer1) return {1.0, -1.0};
+  if (outcome_ == Outcome::kPlayer2) return {-1.0, 1.0};
+  return {0.0, 0.0};
+}
+
+std::string SquadroState::InformationStateString(Player player) const {
+  SPIEL_CHECK_GE(player, 0);
+  SPIEL_CHECK_LT(player, num_players_);
+  return HistoryString();
+}
+
+std::string SquadroState::ObservationString(Player player) const {
+  SPIEL_CHECK_GE(player, 0);
+  SPIEL_CHECK_LT(player, num_players_);
+  return ToString();
+}
+
+int SquadroState::CellToInt(int row, int col) const{
+  std::string str = CellToString(row, col, board_);
+  return cell_state_map_.at(str);
+}
+
+void SquadroState::ObservationTensor(Player player,
+                                         absl::Span<float> values) const {
+  SPIEL_CHECK_GE(player, 0);
+  SPIEL_CHECK_LT(player, num_players_);
+
+  TensorView<2> view(values, {kCellStates, kRows*kCols}, true);
+  for (int row = kRows - 1; row >= 0; --row) {
+    for (int col = 0; col < kCols; ++col) {
+      int cell = row * kCols + col;
+      view[{CellToInt(row, col), cell}] = 1.0;
+    }
+  }
+
+}
+
+std::unique_ptr<State> SquadroState::Clone() const {
+  return std::unique_ptr<State>(new SquadroState(*this));
+}
+
+SquadroGame::SquadroGame(const GameParameters& params)
+    : Game(kGameType, params) {}
+
+SquadroState::SquadroState(std::shared_ptr<const Game> game,
+                                   const std::string& str)
+    : State(game) {
+
+  for (int player = 0; player <= 1; ++player) {
+    for (int pos = 0; pos < kRows; ++pos) {
+      board_[player][pos] = {0, TokenState::missing};
+    }
+  }
+
+  int xs = 0;
+  int os = 0;
+  int r = 6;
+  int c = 0;
+  for (const char ch : str) {
+    switch (ch) {
+      case '.':
+        break;
+      case '^':
+        board_[0][c].position = r;
+        board_[0][c].direction = TokenState::forward;
+        break;
+      case '>':
+        board_[1][r].position = c;
+        board_[1][r].direction = TokenState::forward;
+        break;
+      case 'v':
+        board_[0][c].position = r;
+        board_[0][c].direction = TokenState::backward;
+        break;
+      case '<':
+        board_[1][r].position = c;
+        board_[1][r].direction = TokenState::backward;
+        break;
+      case '0':
+        current_player_ = 0;
+        break;
+      case '1':
+        current_player_ = 1;
+        break;
+      case '2':
+        current_player_ = kTerminalPlayerId;
+        break;
+    }
+    if (ch == '.' || ch == '^' || ch == '>' || ch == 'v' || ch == '<' || ch == 'C') {
+      ++c;
+      if (c >= kCols) {
+        r--;
+        c = 0;
+      }
+    }
+  }
+  SPIEL_CHECK_TRUE(r == -1 && ("Problem parsing state (incorrect rows)."));
+  SPIEL_CHECK_TRUE(c == 1 &&
+                   ("Problem parsing state (column value should be 0)"));
+
+  int count_p0_tokens = 0;
+  int count_p1_tokens = 0;
+  for (int i = 0; i < kNumActions; ++i) {
+    count_p0_tokens += board_[0][i + 1].direction == TokenState::missing ? 0 : 1;
+    count_p1_tokens += board_[1][i + 1].direction == TokenState::missing ? 0 : 1;
+  }
+
+  if (count_p0_tokens == 1) {
+    outcome_ = Outcome::kPlayer1;
+  } else if (count_p1_tokens == 1) {
+    outcome_ = Outcome::kPlayer2;
+  }
+  SPIEL_CHECK_FALSE(count_p0_tokens == 1 && count_p1_tokens == 1 && 
+  ("P1 and P2 cannot both have a single piece."));
+}
+
+}  // namespace squadro
+}  // namespace open_spiel