Implement GameRep::GetInfosets range class (#674)

This replaces the previous implementation of `GameRep::GetInfosets`, which created an explicit container of `GameInfoset` objects, with a new range class that iterates over all personal player information sets on demand.

This is now used in the agent version of liap.

Closes #520.

Author: tturocy

src/core/array.h

@@ -42,6 +42,7 @@ template <class T> class Array {
 public:
   using iterator = typename std::vector<T>::iterator;
   using const_iterator = typename std::vector<T>::const_iterator;
+  using value_type = typename std::vector<T>::value_type;
   using reference = typename std::vector<T>::reference;
   using const_reference = typename std::vector<T>::const_reference;
 

src/core/util.h

@@ -157,6 +157,15 @@ auto minimize_function(const Container &p_container, const Func &p_function)
       [](const T &a, const T &b) -> T { return std::min(a, b); }, p_function);
 }
 
+/// @brief Returns the sum of the function over the container
+template <class Container, class Func>
+auto sum_function(const Container &p_container, const Func &p_function)
+{
+  using T = decltype(p_function(*(p_container.begin())));
+  return std::transform_reduce(p_container.begin(), p_container.end(), static_cast<T>(0),
+                               std::plus<>{}, p_function);
+}
+
 //========================================================================
 //                        Exception classes
 //========================================================================

src/games/game.h

@@ -901,10 +901,12 @@ class GameRep : public std::enable_shared_from_this<GameRep> {
 
   /// @name Information sets
   //@{
+  class Infosets;
+
   /// Returns the iset'th information set in the game (numbered globally)
   virtual GameInfoset GetInfoset(int iset) const { throw UndefinedException(); }
   /// Returns the set of information sets in the game
-  virtual std::vector<GameInfoset> GetInfosets() const { throw UndefinedException(); }
+  virtual Infosets GetInfosets() const;
   /// Sort the information sets for each player in a canonical order
   virtual void SortInfosets() {}
   /// Returns the set of actions taken by the infoset's owner before reaching this infoset
@@ -956,6 +958,83 @@ class GameRep : public std::enable_shared_from_this<GameRep> {
   virtual void BuildComputedValues() const {}
 };
 
+class GameRep::Infosets {
+  Players m_players;
+
+public:
+  explicit Infosets(const Players &outer) : m_players(outer) {}
+
+  class iterator {
+    using OuterIter = Players::iterator;
+    using InnerIter = GamePlayerRep::Infosets::iterator;
+
+    OuterIter m_playerIterator, m_playerEnd;
+    InnerIter m_infosetIterator, m_infosetEnd;
+
+    void next()
+    {
+      while (m_playerIterator != m_playerEnd && m_infosetIterator == m_infosetEnd) {
+        ++m_playerIterator;
+        if (m_playerIterator != m_playerEnd) {
+          auto infosets = (*m_playerIterator)->GetInfosets();
+          m_infosetIterator = infosets.begin();
+          m_infosetEnd = infosets.end();
+        }
+      }
+    }
+
+  public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = GameInfoset;
+    using reference = GameInfoset;
+    using pointer = GameInfoset;
+    using difference_type = std::ptrdiff_t;
+
+    iterator() = default;
+
+    iterator(const OuterIter &p_playerIterator, const OuterIter &p_playerEnd)
+      : m_playerIterator(p_playerIterator), m_playerEnd(p_playerEnd)
+    {
+      if (m_playerIterator != m_playerEnd) {
+        const auto infosets = (*m_playerIterator)->GetInfosets();
+        m_infosetIterator = infosets.begin();
+        m_infosetEnd = infosets.end();
+      }
+      next();
+    }
+
+    reference operator*() const { return *m_infosetIterator; }
+    pointer operator->() const { return *m_infosetIterator; }
+
+    iterator &operator++()
+    {
+      ++m_infosetIterator;
+      next();
+      return *this;
+    }
+
+    iterator operator++(int)
+    {
+      iterator tmp = *this;
+      ++(*this);
+      return tmp;
+    }
+
+    friend bool operator==(const iterator &a, const iterator &b)
+    {
+      return a.m_playerIterator == b.m_playerIterator &&
+             (a.m_playerIterator == a.m_playerEnd || a.m_infosetIterator == b.m_infosetIterator);
+    }
+
+    friend bool operator!=(const iterator &a, const iterator &b) { return !(a == b); }
+  };
+
+  iterator begin() const { return {m_players.begin(), m_players.end()}; }
+  iterator end() const { return {m_players.end(), m_players.end()}; }
+};
+
+inline GameRep::Infosets GameRep::GetInfosets() const { return Infosets(GetPlayers()); }
+
 //=======================================================================
 //          Inline members of game representation classes
 //=======================================================================

src/games/gametree.cc

@@ -1193,15 +1193,6 @@ GameInfoset GameTreeRep::GetInfoset(int p_index) const
   throw std::out_of_range("Infoset index out of range");
 }
 
-std::vector<GameInfoset> GameTreeRep::GetInfosets() const
-{
-  std::vector<GameInfoset> infosets;
-  for (const auto &player : m_players) {
-    std::copy(player->m_infosets.begin(), player->m_infosets.end(), std::back_inserter(infosets));
-  }
-  return infosets;
-}
-
 //------------------------------------------------------------------------
 //                        GameTreeRep: Outcomes
 //------------------------------------------------------------------------

src/games/gametree.h

@@ -126,8 +126,6 @@ class GameTreeRep : public GameExplicitRep {
   //@{
   /// Returns the iset'th information set in the game (numbered globally)
   GameInfoset GetInfoset(int iset) const override;
-  /// Returns the set of information sets in the game
-  std::vector<GameInfoset> GetInfosets() const override;
   /// Sort the information sets for each player in a canonical order
   void SortInfosets() override;
   /// Returns the set of actions taken by the infoset's owner before reaching this infoset

src/solvers/liap/efgliap.cc

@@ -38,18 +38,10 @@ class AgentLyapunovFunction : public FunctionOnSimplices {
     : m_game(p_start.GetGame()), m_profile(p_start)
   {
     m_scale = m_game->GetMaxPayoff() - m_game->GetMinPayoff();
-    if (m_scale == 0.0) {
-      m_scale = 1.0;
-    }
-    else {
-      m_scale = 1.0 / m_scale;
-    }
-
-    for (const auto &player : m_game->GetPlayers()) {
-      for (const auto &infoset : player->GetInfosets()) {
-        m_shape.push_back(infoset->GetActions().size());
-      }
-    }
+    m_scale = (m_scale == 0.0) ? 1.0 : 1.0 / m_scale;
+    std::transform(
+        m_game->GetInfosets().begin(), m_game->GetInfosets().end(), std::back_inserter(m_shape),
+        [](const auto &infoset) -> std::size_t { return infoset->GetActions().size(); });
   }
 
   ~AgentLyapunovFunction() override = default;
@@ -72,35 +64,29 @@ class AgentLyapunovFunction : public FunctionOnSimplices {
 inline double sum_infoset_probs(const MixedBehaviorProfile<double> &p_profile,
                                 const GameInfoset &p_infoset)
 {
-  auto actions = p_infoset->GetActions();
-  return std::accumulate(actions.begin(), actions.end(), 0.0,
-                         [p_profile](double t, const GameAction &a) { return t + p_profile[a]; });
+  return sum_function(p_infoset->GetActions(),
+                      [&p_profile](const auto &action) { return p_profile[action]; });
 }
 
 double
 AgentLyapunovFunction::PenalizedLiapValue(const MixedBehaviorProfile<double> &p_profile) const
 {
   double value = 0.0;
-  // Liapunov function proper - should be replaced with call to profile once
-  // the penalty is removed from that implementation.
-  for (auto player : p_profile.GetGame()->GetPlayers()) {
-    for (auto infoset : player->GetInfosets()) {
-      for (auto action : infoset->GetActions()) {
-        value += sqr(
-            std::max(m_scale * (p_profile.GetPayoff(action) - p_profile.GetPayoff(infoset)), 0.0));
-      }
-    }
+  // Liapunov function proper.
+  for (const auto &infoset : p_profile.GetGame()->GetInfosets()) {
+    double infosetValue = p_profile.GetPayoff(infoset);
+    value += sum_function(infoset->GetActions(), [&](const auto &action) -> double {
+      return sqr(std::max(m_scale * (p_profile.GetPayoff(action) - infosetValue), 0.0));
+    });
   }
   // Penalty function for non-negativity constraint for each action
   for (auto element : static_cast<const Vector<double> &>(p_profile)) {
     value += m_penalty * sqr(std::min(element, 0.0));
   }
   // Penalty function for sum-to-one constraint for each action
-  for (auto player : p_profile.GetGame()->GetPlayers()) {
-    for (auto infoset : player->GetInfosets()) {
-      value += m_penalty * sqr(sum_infoset_probs(m_profile, infoset) - 1.0);
-    }
-  }
+  value += sum_function(p_profile.GetGame()->GetInfosets(), [&](const auto &infoset) -> double {
+    return m_penalty * sqr(sum_infoset_probs(m_profile, infoset) - 1.0);
+  });
   return value;
 }
 
@@ -131,11 +117,9 @@ namespace {
 MixedBehaviorProfile<double> EnforceNonnegativity(const MixedBehaviorProfile<double> &p_profile)
 {
   auto profile = p_profile;
-  for (auto player : p_profile.GetGame()->GetPlayers()) {
-    for (auto infoset : player->GetInfosets()) {
-      for (auto action : infoset->GetActions()) {
-        profile[action] = std::max(profile[action], 0.0);
-      }
+  for (const auto &infoset : p_profile.GetGame()->GetInfosets()) {
+    for (const auto &action : infoset->GetActions()) {
+      profile[action] = std::max(profile[action], 0.0);
     }
   }
   return profile.Normalize();