From: Joost VandeVondele <Joost.VandeVondele@gmail.com>
Date: Sat, 2 Jun 2018 15:02:23 +0000 (+0200)
Subject: Reallocate TT on threadpool resize.
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=6cc56141245abec88861e38e0a44615e4d675813

Reallocate TT on threadpool resize.

Makes sure the potential benefit of first touch does not depend on
the order of the UCI commands Threads and Hash, by reallocating the
hash if a Threads is issued. The cost is zeroing the TT once more
than needed. In case the prefered order (first Threads than Hash)
is employed, this amounts to zeroing the default sized TT (16Mb),
which is essentially instantaneous.

Follow up for https://github.com/official-stockfish/Stockfish/pull/1601
where additional data and discussion is available.

Closes https://github.com/official-stockfish/Stockfish/pull/1620

No functional change.
---

diff --git a/src/main.cpp b/src/main.cpp
index b5067b9b..c5bf3255 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -44,7 +44,6 @@ int main(int argc, char* argv[]) {
   Search::init();
   Pawns::init();
   Tablebases::init(Options["SyzygyPath"]); // After Bitboards are set
-  TT.resize(Options["Hash"]);
   Threads.set(Options["Threads"]);
   Search::clear(); // After threads are up
 
diff --git a/src/thread.cpp b/src/thread.cpp
index cab2d382..43a38e80 100644
--- a/src/thread.cpp
+++ b/src/thread.cpp
@@ -26,6 +26,7 @@
 #include "thread.h"
 #include "uci.h"
 #include "syzygy/tbprobe.h"
+#include "tt.h"
 
 ThreadPool Threads; // Global object
 
@@ -136,6 +137,9 @@ void ThreadPool::set(size_t requested) {
           push_back(new Thread(size()));
       clear();
   }
+
+  // Reallocate the hash with the new threadpool size
+  TT.resize(Options["Hash"]);
 }
 
 /// ThreadPool::clear() sets threadPool data to initial values.
diff --git a/src/tt.cpp b/src/tt.cpp
index 5fa1290b..9f0bc4ba 100644
--- a/src/tt.cpp
+++ b/src/tt.cpp
@@ -36,12 +36,7 @@ TranspositionTable TT; // Our global transposition table
 
 void TranspositionTable::resize(size_t mbSize) {
 
-  size_t newClusterCount = mbSize * 1024 * 1024 / sizeof(Cluster);
-
-  if (newClusterCount == clusterCount)
-      return;
-
-  clusterCount = newClusterCount;
+  clusterCount = mbSize * 1024 * 1024 / sizeof(Cluster);
 
   free(mem);
   mem = malloc(clusterCount * sizeof(Cluster) + CacheLineSize - 1);