Detach the state when copying a position

[stockfish] / src / position.cpp

diff --git a/src/position.cpp b/src/position.cpp
index 93c42291b658d6d90ec9236d2a8642c3073c6037..480a92ec9cfcd1a7e3850aea8fbc94f61c570ece 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
 }
 
 
@@ -1080,21 +1082,17 @@ void Position::do_ep_move(Move m) {
   assert(piece_on(from) == piece_of_color_and_type(us, PAWN));
   assert(piece_on(capsq) == piece_of_color_and_type(them, PAWN));
 
-  // Remove captured piece
+  // Remove captured pawn
   clear_bit(&(byColorBB[them]), capsq);
   clear_bit(&(byTypeBB[PAWN]), capsq);
   clear_bit(&(byTypeBB[0]), capsq); // HACK: byTypeBB[0] == occupied squares
   board[capsq] = EMPTY;
 
-  // Remove moving piece from source square
-  clear_bit(&(byColorBB[us]), from);
-  clear_bit(&(byTypeBB[PAWN]), from);
-  clear_bit(&(byTypeBB[0]), from); // HACK: byTypeBB[0] == occupied squares
-
-  // Put moving piece on destination square
-  set_bit(&(byColorBB[us]), to);
-  set_bit(&(byTypeBB[PAWN]), to);
-  set_bit(&(byTypeBB[0]), to); // HACK: byTypeBB[0] == occupied squares
+  // Move capturing pawn
+  Bitboard move_bb = make_move_bb(from, to);
+  do_move_bb(&(byColorBB[us]), move_bb);
+  do_move_bb(&(byTypeBB[PAWN]), move_bb);
+  do_move_bb(&(byTypeBB[0]), move_bb); // HACK: byTypeBB[0] == occupied squares
   board[to] = board[from];
   board[from] = EMPTY;
 
@@ -1371,22 +1369,18 @@ void Position::undo_ep_move(Move m) {
   assert(piece_on(from) == EMPTY);
   assert(piece_on(capsq) == EMPTY);
 
-  // Replace captured piece
+  // Restore captured pawn
   set_bit(&(byColorBB[them]), capsq);
   set_bit(&(byTypeBB[PAWN]), capsq);
   set_bit(&(byTypeBB[0]), capsq);
   board[capsq] = piece_of_color_and_type(them, PAWN);
 
-  // Remove moving piece from destination square
-  clear_bit(&(byColorBB[us]), to);
-  clear_bit(&(byTypeBB[PAWN]), to);
-  clear_bit(&(byTypeBB[0]), to);
+  // Move capturing pawn back to source square
+  Bitboard move_bb = make_move_bb(to, from);
+  do_move_bb(&(byColorBB[us]), move_bb);
+  do_move_bb(&(byTypeBB[PAWN]), move_bb);
+  do_move_bb(&(byTypeBB[0]), move_bb);
   board[to] = EMPTY;
-
-  // Replace moving piece at source square
-  set_bit(&(byColorBB[us]), from);
-  set_bit(&(byTypeBB[PAWN]), from);
-  set_bit(&(byTypeBB[0]), from);
   board[from] = piece_of_color_and_type(us, PAWN);
 
   // Update piece list
@@ -1614,15 +1608,16 @@ 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
 }
 
 
@@ -1973,7 +1968,7 @@ 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());