Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
- Copyright (C) 2015-2017 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, 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
namespace {
enum Stages {
- MAIN_SEARCH, CAPTURES_INIT, GOOD_CAPTURES, KILLERS, COUNTERMOVE, QUIET_INIT, QUIET, BAD_CAPTURES,
+ MAIN_SEARCH, CAPTURES_INIT, GOOD_CAPTURES, KILLER0, KILLER1, COUNTERMOVE, QUIET_INIT, QUIET, BAD_CAPTURES,
EVASION, EVASIONS_INIT, ALL_EVASIONS,
- PROBCUT, PROBCUT_INIT, PROBCUT_CAPTURES,
- QSEARCH_WITH_CHECKS, QCAPTURES_1_INIT, QCAPTURES_1, QCHECKS,
- QSEARCH_NO_CHECKS, QCAPTURES_2_INIT, QCAPTURES_2,
- QSEARCH_RECAPTURES, QRECAPTURES
+ PROBCUT, PROBCUT_CAPTURES_INIT, PROBCUT_CAPTURES,
+ QSEARCH, QCAPTURES_INIT, QCAPTURES, QCHECKS
};
// partial_insertion_sort() sorts moves in descending order up to and including
/// MovePicker constructor for the main search
MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh,
- const PieceToHistory** ch, Move cm, Move* killers_p)
- : pos(p), mainHistory(mh), contHistory(ch), countermove(cm),
- killers{killers_p[0], killers_p[1]}, depth(d){
+ const CapturePieceToHistory* cph, const PieceToHistory** ch, Move cm, Move* killers_p)
+ : pos(p), mainHistory(mh), captureHistory(cph), contHistory(ch),
+ refutations{killers_p[0], killers_p[1], cm}, depth(d){
assert(d > DEPTH_ZERO);
}
/// MovePicker constructor for quiescence search
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh, Square s)
- : pos(p), mainHistory(mh) {
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh, const CapturePieceToHistory* cph, Square s)
+ : pos(p), mainHistory(mh), captureHistory(cph), recaptureSquare(s), depth(d) {
assert(d <= DEPTH_ZERO);
- if (pos.checkers())
- stage = EVASION;
-
- else if (d > DEPTH_QS_NO_CHECKS)
- stage = QSEARCH_WITH_CHECKS;
-
- else if (d > DEPTH_QS_RECAPTURES)
- stage = QSEARCH_NO_CHECKS;
-
- else
- {
- stage = QSEARCH_RECAPTURES;
- recaptureSquare = s;
- return;
- }
-
- ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
+ stage = pos.checkers() ? EVASION : QSEARCH;
+ ttMove = ttm
+ && pos.pseudo_legal(ttm)
+ && (depth > DEPTH_QS_RECAPTURES || to_sq(ttm) == recaptureSquare) ? ttm : MOVE_NONE;
stage += (ttMove == MOVE_NONE);
}
/// MovePicker constructor for ProbCut: we generate captures with SEE higher
/// than or equal to the given threshold.
-MovePicker::MovePicker(const Position& p, Move ttm, Value th)
- : pos(p), threshold(th) {
+MovePicker::MovePicker(const Position& p, Move ttm, Value th, const CapturePieceToHistory* cph)
+ : pos(p), captureHistory(cph), threshold(th) {
assert(!pos.checkers());
&& pos.pseudo_legal(ttm)
&& pos.capture(ttm)
&& pos.see_ge(ttm, threshold) ? ttm : MOVE_NONE;
-
stage += (ttMove == MOVE_NONE);
}
/// score() assigns a numerical value to each move in a list, used for sorting.
/// Captures are ordered by Most Valuable Victim (MVV), preferring captures
-/// near our home rank. Quiets are ordered using the histories.
+/// with a good history. Quiets are ordered using the histories.
template<GenType Type>
void MovePicker::score() {
for (auto& m : *this)
if (Type == CAPTURES)
m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
- - Value(200 * relative_rank(pos.side_to_move(), to_sq(m)));
+ + (*captureHistory)[pos.moved_piece(m)][to_sq(m)][type_of(pos.piece_on(to_sq(m)))];
else if (Type == QUIETS)
m.value = (*mainHistory)[pos.side_to_move()][from_to(m)]
Move move;
+begin_switch:
+
switch (stage) {
- case MAIN_SEARCH: case EVASION: case QSEARCH_WITH_CHECKS:
- case QSEARCH_NO_CHECKS: case PROBCUT:
+ case MAIN_SEARCH:
+ case EVASION:
+ case QSEARCH:
+ case PROBCUT:
++stage;
return ttMove;
case CAPTURES_INIT:
+ case PROBCUT_CAPTURES_INIT:
+ case QCAPTURES_INIT:
endBadCaptures = cur = moves;
endMoves = generate<CAPTURES>(pos, cur);
score<CAPTURES>();
++stage;
- /* fallthrough */
+
+ // Rebranch at the top of the switch
+ goto begin_switch;
case GOOD_CAPTURES:
while (cur < endMoves)
move = pick_best(cur++, endMoves);
if (move != ttMove)
{
- if (pos.see_ge(move))
+ if (pos.see_ge(move, Value(-55 * (cur-1)->value / 1024)))
return move;
// Losing capture, move it to the beginning of the array
*endBadCaptures++ = move;
}
}
-
++stage;
- move = killers[0]; // First killer move
- if ( move != MOVE_NONE
- && move != ttMove
- && pos.pseudo_legal(move)
- && !pos.capture(move))
- return move;
- /* fallthrough */
- case KILLERS:
- ++stage;
- move = killers[1]; // Second killer move
- if ( move != MOVE_NONE
- && move != ttMove
- && pos.pseudo_legal(move)
- && !pos.capture(move))
- return move;
+ // If the countermove is the same as a killer, skip it
+ if ( refutations[0] == refutations[2]
+ || refutations[1] == refutations[2])
+ refutations[2] = MOVE_NONE;
+
/* fallthrough */
+ case KILLER0:
+ case KILLER1:
case COUNTERMOVE:
- ++stage;
- move = countermove;
- if ( move != MOVE_NONE
- && move != ttMove
- && move != killers[0]
- && move != killers[1]
- && pos.pseudo_legal(move)
- && !pos.capture(move))
- return move;
+ while (stage <= COUNTERMOVE)
+ {
+ move = refutations[ stage++ - KILLER0 ];
+ if ( move != MOVE_NONE
+ && move != ttMove
+ && pos.pseudo_legal(move)
+ && !pos.capture(move))
+ return move;
+ }
/* fallthrough */
case QUIET_INIT:
/* fallthrough */
case QUIET:
- while ( cur < endMoves
- && (!skipQuiets || cur->value >= VALUE_ZERO))
- {
- move = *cur++;
-
- if ( move != ttMove
- && move != killers[0]
- && move != killers[1]
- && move != countermove)
- return move;
- }
+ if (!skipQuiets)
+ while (cur < endMoves)
+ {
+ move = *cur++;
+ if ( move != ttMove
+ && move != refutations[0]
+ && move != refutations[1]
+ && move != refutations[2])
+ return move;
+ }
++stage;
cur = moves; // Point to beginning of bad captures
/* fallthrough */
}
break;
- case PROBCUT_INIT:
- cur = moves;
- endMoves = generate<CAPTURES>(pos, cur);
- score<CAPTURES>();
- ++stage;
- /* fallthrough */
-
case PROBCUT_CAPTURES:
while (cur < endMoves)
{
}
break;
- case QCAPTURES_1_INIT: case QCAPTURES_2_INIT:
- cur = moves;
- endMoves = generate<CAPTURES>(pos, cur);
- score<CAPTURES>();
- ++stage;
- /* fallthrough */
-
- case QCAPTURES_1: case QCAPTURES_2:
+ case QCAPTURES:
while (cur < endMoves)
{
move = pick_best(cur++, endMoves);
- if (move != ttMove)
+ if ( move != ttMove
+ && (depth > DEPTH_QS_RECAPTURES || to_sq(move) == recaptureSquare))
return move;
}
- if (stage == QCAPTURES_2)
+ if (depth <= DEPTH_QS_NO_CHECKS)
break;
cur = moves;
endMoves = generate<QUIET_CHECKS>(pos, cur);
case QCHECKS:
while (cur < endMoves)
{
- move = cur++->move;
+ move = *cur++;
if (move != ttMove)
return move;
}
break;
- case QSEARCH_RECAPTURES:
- cur = moves;
- endMoves = generate<CAPTURES>(pos, cur);
- score<CAPTURES>();
- ++stage;
- /* fallthrough */
-
- case QRECAPTURES:
- while (cur < endMoves)
- {
- move = pick_best(cur++, endMoves);
- if (to_sq(move) == recaptureSquare)
- return move;
- }
- break;
-
default:
assert(false);
}
projects / stockfish / blobdiff