Extract only exact scores to get the PV

[stockfish] / src / movepick.cpp

diff --git a/src/movepick.cpp b/src/movepick.cpp
index 901aa60e5625c766b797fd88d4dec2888b24ac69..63f77dbaebfc14570cb4ff56408348fa4b15adb0 100644 (file)
--- a/src/movepick.cpp
+++ b/src/movepick.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) 2008-2009 Marco Costalba
+  Copyright (C) 2008-2010 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
@@ -70,17 +70,18 @@ namespace {
 /// search captures, promotions and some checks) and about how important good
 /// move ordering is at the current node.
 
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d,
-                       const History& h, SearchStack* ss) : pos(p), H(h) {
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h,
+                       SearchStack* ss, Value beta) : pos(p), H(h) {
   int searchTT = ttm;
   ttMoves[0].move = ttm;
+  badCaptureThreshold = 0;
   lastBadCapture = badCaptures;
 
   pinned = p.pinned_pieces(pos.side_to_move());
 
   if (ss && !p.is_check())
   {
-      ttMoves[1].move = (ss->mateKiller == ttm)? MOVE_NONE : ss->mateKiller;
+      ttMoves[1].move = (ss->mateKiller == ttm) ? MOVE_NONE : ss->mateKiller;
       searchTT |= ttMoves[1].move;
       killers[0].move = ss->killers[0];
       killers[1].move = ss->killers[1];
@@ -90,7 +91,14 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d,
   if (p.is_check())
       phasePtr = EvasionsPhaseTable;
   else if (d > Depth(0))
+  {
+      // Consider sligtly negative captures as good if at low
+      // depth and far from beta.
+      if (ss && ss->eval < beta - PawnValueMidgame && d < 3 * OnePly)
+          badCaptureThreshold = -PawnValueMidgame;
+
       phasePtr = MainSearchPhaseTable;
+  }
   else if (d == Depth(0))
       phasePtr = QsearchWithChecksPhaseTable;
   else
@@ -104,7 +112,7 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d,
           searchTT = ttMoves[0].move = MOVE_NONE;
   }
 
-  phasePtr += !searchTT - 1;
+  phasePtr += int(!searchTT) - 1;
   go_next_phase();
 }
 
@@ -136,7 +144,7 @@ void MovePicker::go_next_phase() {
   case PH_NONCAPTURES:
       lastMove = generate_noncaptures(pos, moves);
       score_noncaptures();
-      sort_moves(moves, lastMove);
+      sort_moves(moves, lastMove, &lastGoodNonCapture);
       return;
 
   case PH_BAD_CAPTURES:
@@ -213,6 +221,7 @@ void MovePicker::score_noncaptures() {
   Move m;
   Piece piece;
   Square from, to;
+  int hs;
 
   for (MoveStack* cur = moves; cur != lastMove; cur++)
   {
@@ -220,7 +229,14 @@ void MovePicker::score_noncaptures() {
       from = move_from(m);
       to = move_to(m);
       piece = pos.piece_on(from);
-      cur->score = H.move_ordering_score(piece, to);
+      hs = H.move_ordering_score(piece, to);
+
+      // Ensure history has always highest priority
+      if (hs > 0)
+          hs += 10000;
+
+      // Gain table based scoring
+      cur->score = hs + 16 * H.gain(piece, to);
   }
 }
 
@@ -240,7 +256,7 @@ void MovePicker::score_evasions_or_checks() {
   {
       m = cur->move;
       if ((seeScore = pos.see_sign(m)) < 0)
-          cur->score = seeScore;
+          cur->score = seeScore - HistoryMax; // Be sure are at the bottom
       else if (pos.move_is_capture(m))
           cur->score =  pos.midgame_value_of_piece_on(move_to(m))
                       - pos.type_of_piece_on(move_from(m)) + HistoryMax;
@@ -282,7 +298,7 @@ Move MovePicker::get_next_move() {
               {
                   // Check for a non negative SEE now
                   int seeValue = pos.see_sign(move);
-                  if (seeValue >= 0)
+                  if (seeValue >= badCaptureThreshold)
                       return move;
 
                   // Losing capture, move it to the badCaptures[] array, note
@@ -297,14 +313,19 @@ Move MovePicker::get_next_move() {
           case PH_KILLERS:
               move = (curMove++)->move;
               if (   move != MOVE_NONE
+                  && move_is_legal(pos, move, pinned)
                   && move != ttMoves[0].move
                   && move != ttMoves[1].move
-                  && move_is_legal(pos, move, pinned)
                   && !pos.move_is_capture(move))
                   return move;
               break;
 
           case PH_NONCAPTURES:
+
+              // Sort negative scored moves only when we get there
+              if (curMove == lastGoodNonCapture)
+                  insertion_sort(lastGoodNonCapture, lastMove);
+
               move = (curMove++)->move;
               if (   move != ttMoves[0].move
                   && move != ttMoves[1].move