From: Joost VandeVondele <Joost.VandeVondele@gmail.com>
Date: Thu, 31 Aug 2017 07:34:32 +0000 (+0200)
Subject: Fix uninitialized memory usage
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=e385f194e970f0675bd4c3509bca4a6c81b6df5e;hp=7b4c9852e1421ebe6ec326c38f04ad575ad91053;ds=sidebyside

Fix uninitialized memory usage

After increasing the number of threads, the histories were not cleared,
resulting in uninitialized memory usage.

This patch fixes this by clearing threads histories in Thread c'tor as
is the idomatic way.

This fixes issue 1227

No functional change.
---

diff --git a/src/search.cpp b/src/search.cpp
index 1e70be60..7873e7dc 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -75,9 +75,6 @@ namespace {
   int FutilityMoveCounts[2][16]; // [improving][depth]
   int Reductions[2][2][64][64];  // [pv][improving][depth][moveNumber]
 
-  // Threshold used for countermoves based pruning
-  const int CounterMovePruneThreshold = 0;
-
   template <bool PvNode> Depth reduction(bool i, Depth d, int mn) {
     return Reductions[PvNode][i][std::min(d / ONE_PLY, 63)][std::min(mn, 63)] * ONE_PLY;
   }
@@ -219,16 +216,7 @@ void Search::clear() {
   TT.clear();
 
   for (Thread* th : Threads)
-  {
-      th->counterMoves.fill(MOVE_NONE);
-      th->mainHistory.fill(0);
-
-      for (auto& to : th->contHistory)
-          for (auto& h : to)
-              h.fill(0);
-
-      th->contHistory[NO_PIECE][0].fill(CounterMovePruneThreshold - 1);
-  }
+      th->clear();
 
   Threads.main()->callsCnt = 0;
   Threads.main()->previousScore = VALUE_INFINITE;
diff --git a/src/search.h b/src/search.h
index 2e08b550..694dd643 100644
--- a/src/search.h
+++ b/src/search.h
@@ -31,6 +31,10 @@ class Position;
 
 namespace Search {
 
+/// Threshold used for countermoves based pruning
+const int CounterMovePruneThreshold = 0;
+
+
 /// Stack struct keeps track of the information we need to remember from nodes
 /// shallower and deeper in the tree during the search. Each search thread has
 /// its own array of Stack objects, indexed by the current ply.
diff --git a/src/thread.cpp b/src/thread.cpp
index 208cb0b1..d095aefe 100644
--- a/src/thread.cpp
+++ b/src/thread.cpp
@@ -35,6 +35,7 @@ ThreadPool Threads; // Global object
 Thread::Thread(size_t n) : idx(n), stdThread(&Thread::idle_loop, this) {
 
   wait_for_search_finished();
+  clear(); // Zero-init histories (based on std::array)
 }
 
 
@@ -51,6 +52,20 @@ Thread::~Thread() {
 }
 
 
+/// Thread::clear() reset histories, usually before a new game
+
+void Thread::clear() {
+
+  counterMoves.fill(MOVE_NONE);
+  mainHistory.fill(0);
+
+  for (auto& to : contHistory)
+      for (auto& h : to)
+          h.fill(0);
+
+  contHistory[NO_PIECE][0].fill(Search::CounterMovePruneThreshold - 1);
+}
+
 /// Thread::start_searching() wakes up the thread that will start the search
 
 void Thread::start_searching() {
diff --git a/src/thread.h b/src/thread.h
index 8c0a6665..093b9512 100644
--- a/src/thread.h
+++ b/src/thread.h
@@ -52,6 +52,7 @@ public:
   explicit Thread(size_t);
   virtual ~Thread();
   virtual void search();
+  void clear();
   void idle_loop();
   void start_searching();
   void wait_for_search_finished();