Skip castle rights update when not needed

[stockfish] / src / position.cpp

diff --git a/src/position.cpp b/src/position.cpp
index f4752c5e318c5dc8be0f51898b547b7a032e2505..c17c5c5757e550680ee9929e144dcbf5bf3f2216 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -27,6 +27,7 @@
 #include <fstream>
 #include <iostream>
 
+#include "bitcount.h"
 #include "mersenne.h"
 #include "movegen.h"
 #include "movepick.h"
@@ -314,9 +315,10 @@ void Position::print(Move m) const {
 
 /// Position::copy() creates a copy of the input position.
 
-void Position::copy(const Position &pos) {
+void Position::copy(const Position& pos) {
 
   memcpy(this, &pos, sizeof(Position));
+  saveState(); // detach and copy state info
 }
 
 
@@ -794,11 +796,14 @@ void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
     pieceList[us][piece][index[from]] = to;
     index[to] = index[from];
 
-    // Update castle rights
-    st->key ^= zobCastle[st->castleRights];
-    st->castleRights &= castleRightsMask[from];
-    st->castleRights &= castleRightsMask[to];
-    st->key ^= zobCastle[st->castleRights];
+    // Update castle rights, try to shortcut a common case
+    if ((castleRightsMask[from] & castleRightsMask[to]) != ALL_CASTLES)
+    {
+        st->key ^= zobCastle[st->castleRights];
+        st->castleRights &= castleRightsMask[from];
+        st->castleRights &= castleRightsMask[to];
+        st->key ^= zobCastle[st->castleRights];
+    }
 
     // Update checkers bitboard, piece must be already moved
     st->checkersBB = EmptyBoardBB;
@@ -1592,7 +1597,7 @@ int Position::see(Square from, Square to) const {
       if (pt == KING && stmAttackers)
       {
           assert(n < 32);
-          swapList[n++] = 100;
+          swapList[n++] = QueenValueMidgame*10;
           break;
       }
   } while (stmAttackers);
@@ -1606,15 +1611,16 @@ int Position::see(Square from, Square to) const {
 }
 
 
-/// Position::setStartState() copies the content of the argument
+/// Position::saveState() copies the content of the current state
 /// inside startState and makes st point to it. This is needed
 /// when the st pointee could become stale, as example because
 /// the caller is about to going out of scope.
 
-void Position::setStartState(const StateInfo& s) {
+void Position::saveState() {
 
-  startState = s;
+  startState = *st;
   st = &startState;
+  st->previous = NULL; // as a safe guard
 }
 
 
@@ -1965,7 +1971,7 @@ void Position::init_piece_square_tables() {
 /// the white and black sides reversed. This is only useful for debugging,
 /// especially for finding evaluation symmetry bugs.
 
-void Position::flipped_copy(const Position &pos) {
+void Position::flipped_copy(const Position& pos) {
 
   assert(pos.is_ok());