Micro-optimize SEE

[stockfish] / src / position.cpp

diff --git a/src/position.cpp b/src/position.cpp
index d29e77135e6e1883fae2319bc44e9b0ed66970d7..8d4b9f4f3c53de66f382dee30529aa46986ae91e 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -1,7 +1,7 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
-  Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
+  Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -47,7 +47,7 @@ namespace Zobrist {
   Key exclusion;
 }
 
-Key Position::exclusion_key() const { return st->key ^ Zobrist::exclusion;}
+Key Position::exclusion_key() const { return st->key ^ Zobrist::exclusion; }
 
 namespace {
 
@@ -176,9 +176,8 @@ void Position::init() {
 }
 
 
-/// Position::operator=() creates a copy of 'pos'. We want the new born Position
-/// object to not depend on any external data so we detach state pointer from
-/// the source one.
+/// Position::operator=() creates a copy of 'pos' but detaching the state pointer
+/// from the source to be self-consistent and not depending on any external data.
 
 Position& Position::operator=(const Position& pos) {
 
@@ -642,7 +641,7 @@ bool Position::gives_check(Move m, const CheckInfo& ci) const {
       return true;
 
   // Is there a discovered check?
-  if (   unlikely(ci.dcCandidates)
+  if (    ci.dcCandidates
       && (ci.dcCandidates & from)
       && !aligned(from, to, ci.ksq))
       return true;
@@ -871,7 +870,7 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI
               st->checkersBB |= to;
 
           // Discovered checks
-          if (unlikely(ci.dcCandidates) && (ci.dcCandidates & from))
+          if (ci.dcCandidates && (ci.dcCandidates & from))
           {
               if (pt != ROOK)
                   st->checkersBB |= attacks_from<ROOK>(king_square(them)) & pieces(us, QUEEN, ROOK);
@@ -1061,8 +1060,8 @@ Value Position::see(Move m) const {
   stm = color_of(piece_on(from));
   occupied = pieces() ^ from;
 
-  // Castling moves are implemented as king capturing the rook so cannot be
-  // handled correctly. Simply return 0 that is always the correct value
+  // Castling moves are implemented as king capturing the rook so cannot
+  // be handled correctly. Simply return VALUE_ZERO that is always correct
   // unless in the rare case the rook ends up under attack.
   if (type_of(m) == CASTLING)
       return VALUE_ZERO;
@@ -1099,21 +1098,11 @@ Value Position::see(Move m) const {
 
       // Locate and remove the next least valuable attacker
       captured = min_attacker<PAWN>(byTypeBB, to, stmAttackers, occupied, attackers);
-
-      // Stop before processing a king capture
-      if (captured == KING)
-      {
-          if (stmAttackers == attackers)
-              ++slIndex;
-
-          break;
-      }
-
       stm = ~stm;
       stmAttackers = attackers & pieces(stm);
       ++slIndex;
 
-  } while (stmAttackers);
+  } while (stmAttackers && (captured != KING || (--slIndex, false))); // Stop before a king capture
 
   // Having built the swap list, we negamax through it to find the best
   // achievable score from the point of view of the side to move.
@@ -1148,10 +1137,6 @@ bool Position::is_draw() const {
 /// Position::flip() flips position with the white and black sides reversed. This
 /// is only useful for debugging e.g. for finding evaluation symmetry bugs.
 
-static char toggle_case(char c) {
-  return char(islower(c) ? toupper(c) : tolower(c));
-}
-
 void Position::flip() {
 
   string f, token;
@@ -1169,7 +1154,8 @@ void Position::flip() {
   ss >> token; // Castling availability
   f += token + " ";
 
-  std::transform(f.begin(), f.end(), f.begin(), toggle_case);
+  std::transform(f.begin(), f.end(), f.begin(),
+                 [](char c) { return char(islower(c) ? toupper(c) : tolower(c)); });
 
   ss >> token; // En passant square
   f += (token == "-" ? token : token.replace(1, 1, token[1] == '3' ? "6" : "3"));