From: Marco Costalba <mcostalba@gmail.com>
Date: Mon, 25 Jan 2010 15:22:50 +0000 (+0100)
Subject: Avoid copy a Position to get a move's san notation
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=d844a75d2c12e4888443e47cb7b0effd78d81bb8

Avoid copy a Position to get a move's san notation

In move_to_san() we create by copy a new position just
to detect if move gives check. This could be very costly in
line_to_san() that calls move_to_san() for every move, so
create the position only once and pass a reference to move_to_san()

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---

diff --git a/src/position.cpp b/src/position.cpp
index 2b6e2b4c..a389e9c0 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -356,8 +356,9 @@ void Position::print(Move m) const {
   std::cout << std::endl;
   if (m != MOVE_NONE)
   {
+      Position p(*this);
       string col = (color_of_piece_on(move_from(m)) == BLACK ? ".." : "");
-      std::cout << "Move is: " << col << move_to_san(*this, m) << std::endl;
+      std::cout << "Move is: " << col << move_to_san(p, m) << std::endl;
   }
   for (Rank rank = RANK_8; rank >= RANK_1; rank--)
   {
diff --git a/src/san.cpp b/src/san.cpp
index f1558878..2d5dca3f 100644
--- a/src/san.cpp
+++ b/src/san.cpp
@@ -63,7 +63,7 @@ namespace {
 /// that the move is a legal move from the position. The return value is
 /// a string containing the move in short algebraic notation.
 
-const string move_to_san(const Position& pos, Move m) {
+const string move_to_san(Position& pos, Move m) {
 
   assert(pos.is_ok());
   assert(move_is_ok(m));
@@ -123,10 +123,10 @@ const string move_to_san(const Position& pos, Move m) {
   // Position::move_is_check doesn't detect all checks (not castling moves,
   // promotions and en passant captures).
   StateInfo st;
-  Position p(pos);
-  p.do_move(m, st);
-  if (p.is_check())
-      san += p.is_mate()? "#" : "+";
+  pos.do_move(m, st);
+  if (pos.is_check())
+      san += pos.is_mate() ? "#" : "+";
+  pos.undo_move(m);
 
   return san;
 }
diff --git a/src/san.h b/src/san.h
index 42202cfa..f398e695 100644
--- a/src/san.h
+++ b/src/san.h
@@ -36,7 +36,7 @@
 //// Prototypes
 ////
 
-extern const std::string move_to_san(const Position& pos, Move m);
+extern const std::string move_to_san(Position& pos, Move m);
 extern Move move_from_san(const Position& pos, const std::string& str);
 extern const std::string line_to_san(const Position& pos, Move line[], int startColumn, bool breakLines);
 extern const std::string pretty_pv(const Position& pos, int time, int depth, uint64_t nodes, Value score, ValueType type, Move pv[]);