From bccda0375af970829208731feda2bb13aea1118a Mon Sep 17 00:00:00 2001
From: drdkad <d.a.kadnikov@gmail.com>
Date: Wed, 22 Jul 2026 10:22:52 +0100
Subject: [PATCH] Correct sparsity violation in representation of behaviour
 associated with a strategy

---
 ChangeLog             | 3 +++
 src/games/game.cc     | 7 ++++---
 src/games/gametree.cc | 2 +-
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 9704c98b4..19e30ae56 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -8,6 +8,9 @@
 - Implemented bespoke XML parser that handles the subset in the de-facto legacy XML workbook .gbt format;
   removes dependency on tinyxml.  (#897)
 
+### Fixed
+- Converting a behavior profile to a strategy profile, and computing pure-strategy payoffs
+  no longer inserts spurious entries into a strategy's internal action map.
 
 ## [16.7.0] - 2026-07-11
 
diff --git a/src/games/game.cc b/src/games/game.cc
index f912c8179..79c5cd7dd 100644
--- a/src/games/game.cc
+++ b/src/games/game.cc
@@ -96,7 +96,7 @@ void GamePlayerRep::MakeStrategy(const std::map<GameInfosetRep *, int> &behav)
   strategy->m_behav = behav;
   for (const auto &infoset : m_infosets) {
     strategy->m_label += (contains(strategy->m_behav, infoset.get()))
-                             ? std::to_string(strategy->m_behav[infoset.get()])
+                             ? std::to_string(strategy->m_behav.at(infoset.get()))
                              : "*";
   }
   if (strategy->m_label.empty()) {
@@ -305,8 +305,9 @@ MixedStrategyProfile<T>::MixedStrategyProfile(const MixedBehaviorProfile<T> &p_p
     for (const auto &strategy : player->m_strategies) {
       auto prob = static_cast<T>(1);
       for (const auto &infoset : player->m_infosets) {
-        if (strategy->m_behav[infoset.get()] > 0) {
-          prob *= p_profile[infoset->GetAction(strategy->m_behav[infoset.get()])];
+        if (contains(strategy->m_behav, infoset.get()) &&
+            strategy->m_behav.at(infoset.get()) > 0) {
+          prob *= p_profile[infoset->GetAction(strategy->m_behav.at(infoset.get()))];
         }
       }
       (*m_rep)[strategy] = prob;
diff --git a/src/games/gametree.cc b/src/games/gametree.cc
index 535d1db19..84d6ec0fd 100644
--- a/src/games/gametree.cc
+++ b/src/games/gametree.cc
@@ -1741,7 +1741,7 @@ Rational TreePureStrategyProfileRep::GetPayoff(const GamePlayer &p_player) const
   for (const auto &player : m_game->GetPlayers()) {
     for (const auto &infoset : player->GetInfosets()) {
       try {
-        behav.SetAction(infoset->GetAction(GetStrategy(player)->m_behav[infoset.get()]));
+        behav.SetAction(infoset->GetAction(GetStrategy(player)->m_behav.at(infoset.get())));
       }
       catch (std::out_of_range &) {
       }