In pure strategy profile compute strategy by mixed-radix arithmetic rather than map lookup.

Author: tturocy

src/games/game.cc

@@ -184,15 +184,16 @@ GameRep::~GameRep()
 
 void GameRep::IndexStrategies() const
 {
-  long offset = 1L;
-  for (auto player : m_players) {
-    int st = 1;
-    for (auto strategy : player->m_strategies) {
-      strategy->m_number = st;
-      strategy->m_offset = (st - 1) * offset;
-      st++;
+  long stride = 1L;
+  for (const auto player : m_players) {
+    player->m_stride = stride;
+    int digit = 0;
+    for (const auto strategy : player->m_strategies) {
+      strategy->m_number = digit + 1;
+      strategy->m_offset = digit * stride;
+      ++digit;
     }
-    offset *= player->m_strategies.size();
+    stride *= player->m_strategies.size();
   }
 }
 

src/games/game.h

@@ -363,6 +363,7 @@ class GamePlayerRep : public std::enable_shared_from_this<GamePlayerRep> {
   friend class GameInfosetRep;
   friend class GameNodeRep;
   friend class StrategySupportProfile;
+  friend class PureStrategyProfileRep;
   template <class T> friend class MixedBehaviorProfile;
   template <class T> friend class MixedStrategyProfile;
 
@@ -378,6 +379,8 @@ class GamePlayerRep : public std::enable_shared_from_this<GamePlayerRep> {
   bool m_valid{true};
   GameRep *m_game;
   int m_number;
+  // The stride of the player into the set of pure strategy profiles
+  long m_stride{0};
   std::string m_label;
   std::vector<std::shared_ptr<GameInfosetRep>> m_infosets;
   std::vector<std::shared_ptr<GameStrategyRep>> m_strategies;

src/games/stratpure.h

@@ -61,9 +61,12 @@ class PureStrategyProfileRep {
   const Game &GetGame() const { return m_nfg; }
 
   /// Get the strategy played by the player
-  const GameStrategy &GetStrategy(const GamePlayer &p_player) const
+  GameStrategy GetStrategy(const GamePlayer &p_player) const
   {
-    return m_profile.at(p_player);
+    const long stride = p_player->m_stride;
+    const long radix = p_player->m_strategies.size();
+    const long digit = (m_index / stride) % radix;
+    return p_player->m_strategies[digit];
   }
 
   /// Set the strategy for a player