From 0ff91e16da5d66d7b47274203d460ff0144f1e39 Mon Sep 17 00:00:00 2001
From: Marco Costalba <mcostalba@gmail.com>
Date: Mon, 25 Jan 2010 12:44:30 +0100
Subject: [PATCH] Do not copy master position in split()

A pointer is enough because after a split point has been
setup master and slaves thread end up calling sp_search() or
sp_search_pv() and here a full copy of split point position is
done again, note that even master does another copy (of itself)
and this is done before any do_move() call so that master Position
is never updated between split() and sp_search().

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---
 src/position.h |  4 ++--
 src/search.cpp | 13 ++++---------
 src/thread.h   |  2 +-
 src/uci.cpp    |  2 +-
 4 files changed, 8 insertions(+), 13 deletions(-)

diff --git a/src/position.h b/src/position.h
index e7dc3a80..c4dbfcf6 100644
--- a/src/position.h
+++ b/src/position.h
@@ -147,8 +147,8 @@ public:
 
   // Constructors
   Position();
-  Position(const Position& pos);
-  Position(const std::string& fen);
+  explicit Position(const Position& pos);
+  explicit Position(const std::string& fen);
 
   // Text input/output
   void from_fen(const std::string& fen);
diff --git a/src/search.cpp b/src/search.cpp
index 2244a2f7..1c271561 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1813,8 +1813,7 @@ namespace {
     assert(threadID >= 0 && threadID < ActiveThreads);
     assert(ActiveThreads > 1);
 
-    Position pos;
-    pos.fast_copy(sp->pos);
+    Position pos(*sp->pos);
     CheckInfo ci(pos);
     SearchStack* ss = sp->sstack[threadID];
     Value value = -VALUE_INFINITE;
@@ -1956,8 +1955,7 @@ namespace {
     assert(threadID >= 0 && threadID < ActiveThreads);
     assert(ActiveThreads > 1);
 
-    Position pos;
-    pos.fast_copy(sp->pos);
+    Position pos(*sp->pos);
     CheckInfo ci(pos);
     SearchStack* ss = sp->sstack[threadID];
     Value value = -VALUE_INFINITE;
@@ -2969,7 +2967,7 @@ namespace {
     splitPoint = SplitPointStack[master] + Threads[master].activeSplitPoints;
     Threads[master].activeSplitPoints++;
 
-    // Initialize the split point object and copy current position
+    // Initialize the split point object
     splitPoint->parent = Threads[master].splitPoint;
     splitPoint->finished = false;
     splitPoint->ply = ply;
@@ -2983,14 +2981,11 @@ namespace {
     splitPoint->mp = mp;
     splitPoint->moves = *moves;
     splitPoint->cpus = 1;
-    splitPoint->pos.fast_copy(p);
+    splitPoint->pos = &p;
     splitPoint->parentSstack = sstck;
     for (i = 0; i < ActiveThreads; i++)
         splitPoint->slaves[i] = 0;
 
-    // Detach splitPoint Position from the master one
-    splitPoint->pos.detach();
-
     // Copy the tail of current search stack to the master thread
     memcpy(splitPoint->sstack[master] + ply - 1, sstck + ply - 1, 3 * sizeof(SearchStack));
     Threads[master].splitPoint = splitPoint;
diff --git a/src/thread.h b/src/thread.h
index 2ac96813..d12ec845 100644
--- a/src/thread.h
+++ b/src/thread.h
@@ -46,7 +46,7 @@ const int ACTIVE_SPLIT_POINTS_MAX = 8;
 
 struct SplitPoint {
   SplitPoint *parent;
-  Position pos;
+  const Position* pos;
   SearchStack sstack[THREAD_MAX][PLY_MAX_PLUS_2];
   SearchStack *parentSstack;
   int ply;
diff --git a/src/uci.cpp b/src/uci.cpp
index 21bbb884..3812a379 100644
--- a/src/uci.cpp
+++ b/src/uci.cpp
@@ -314,7 +314,7 @@ namespace {
 
     string token;
     int depth, tm, n;
-    Position pos = RootPosition;
+    Position pos(RootPosition);
 
     if (!(uip >> depth))
         return;
-- 
2.39.2