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
#include <cassert>
#include "movepick.h"
-#include "thread.h"
namespace {
enum Stages {
MAIN_SEARCH, CAPTURES_INIT, GOOD_CAPTURES, KILLERS, 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, QSEARCH_RECAPTURES, QRECAPTURES
};
- // An insertion sort, which sorts moves in descending order up to and including a given limit.
- // The order of moves smaller than the limit is left unspecified.
- // To keep the implementation simple, *begin is always included in the list of sorted moves.
- void partial_insertion_sort(ExtMove* begin, ExtMove* end, Value limit)
- {
- for (ExtMove *sortedEnd = begin + 1, *p = begin + 1; p < end; ++p)
+ // partial_insertion_sort() sorts moves in descending order up to and including
+ // a given limit. The order of moves smaller than the limit is left unspecified.
+ void partial_insertion_sort(ExtMove* begin, ExtMove* end, int limit) {
+
+ for (ExtMove *sortedEnd = begin, *p = begin + 1; p < end; ++p)
if (p->value >= limit)
{
ExtMove tmp = *p, *q;
- *p = *sortedEnd;
- for (q = sortedEnd; q != begin && *(q-1) < tmp; --q)
- *q = *(q-1);
+ *p = *++sortedEnd;
+ for (q = sortedEnd; q != begin && *(q - 1) < tmp; --q)
+ *q = *(q - 1);
*q = tmp;
- ++sortedEnd;
}
}
// pick_best() finds the best move in the range (begin, end) and moves it to
// the front. It's faster than sorting all the moves in advance when there
// are few moves, e.g., the possible captures.
- Move pick_best(ExtMove* begin, ExtMove* end)
- {
- std::swap(*begin, *std::max_element(begin, end));
- return *begin;
+ Move pick_best(ExtMove* begin, ExtMove* end) {
+
+ std::swap(*begin, *std::max_element(begin, end));
+ return *begin;
}
} // namespace
/// search captures, promotions, and some checks) and how important good move
/// ordering is at the current node.
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d, Search::Stack* s)
- : pos(p), ss(s), depth(d) {
+/// MovePicker constructor for the main search
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh,
+ const CapturePieceToHistory* cph, const PieceToHistory** ch, Move cm, Move* killers_p)
+ : pos(p), mainHistory(mh), captureHistory(cph), contHistory(ch), countermove(cm),
+ killers{killers_p[0], killers_p[1]}, depth(d){
assert(d > DEPTH_ZERO);
- Square prevSq = to_sq((ss-1)->currentMove);
- countermove = pos.this_thread()->counterMoves[pos.piece_on(prevSq)][prevSq];
-
stage = pos.checkers() ? EVASION : MAIN_SEARCH;
ttMove = ttm && pos.pseudo_legal(ttm) ? ttm : MOVE_NONE;
stage += (ttMove == MOVE_NONE);
}
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d, Square s)
- : pos(p) {
+/// MovePicker constructor for quiescence search
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh, const CapturePieceToHistory* cph, Square s)
+ : pos(p), mainHistory(mh), captureHistory(cph), 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;
+ stage = QSEARCH;
else
{
stage += (ttMove == MOVE_NONE);
}
-MovePicker::MovePicker(const Position& p, Move ttm, Value th)
- : pos(p), threshold(th) {
+/// 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, const CapturePieceToHistory* cph)
+ : pos(p), captureHistory(cph), threshold(th) {
assert(!pos.checkers());
stage = PROBCUT;
-
- // In ProbCut we generate captures with SEE higher than or equal to the given threshold
ttMove = ttm
&& pos.pseudo_legal(ttm)
&& pos.capture(ttm)
- && pos.see_ge(ttm, threshold)? ttm : MOVE_NONE;
+ && 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
+/// with a good history. Quiets are ordered using the histories.
+template<GenType Type>
+void MovePicker::score() {
-/// score() assigns a numerical value to each move in a move list. The moves with
-/// highest values will be picked first.
-template<>
-void MovePicker::score<CAPTURES>() {
- // Winning and equal captures in the main search are ordered by MVV, preferring
- // captures near our home rank. Surprisingly, this appears to perform slightly
- // better than SEE-based move ordering: exchanging big pieces before capturing
- // a hanging piece probably helps to reduce the subtree size.
- // In the main search we want to push captures with negative SEE values to the
- // badCaptures[] array, but instead of doing it now we delay until the move
- // has been picked up, saving some SEE calls in case we get a cutoff.
- for (auto& m : *this)
- m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
- - Value(200 * relative_rank(pos.side_to_move(), to_sq(m)));
-}
-
-template<>
-void MovePicker::score<QUIETS>() {
-
- const HistoryStats& history = pos.this_thread()->history;
-
- const CounterMoveStats& cmh = *(ss-1)->counterMoves;
- const CounterMoveStats& fmh = *(ss-2)->counterMoves;
- const CounterMoveStats& fm2 = *(ss-4)->counterMoves;
-
- Color c = pos.side_to_move();
+ static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type");
for (auto& m : *this)
- m.value = cmh[pos.moved_piece(m)][to_sq(m)]
- + fmh[pos.moved_piece(m)][to_sq(m)]
- + fm2[pos.moved_piece(m)][to_sq(m)]
- + history.get(c, m);
-}
+ if (Type == CAPTURES)
+ m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
+ + Value((*captureHistory)[pos.moved_piece(m)][to_sq(m)][type_of(pos.piece_on(to_sq(m)))]);
-template<>
-void MovePicker::score<EVASIONS>() {
- // Try captures ordered by MVV/LVA, then non-captures ordered by stats heuristics
- const HistoryStats& history = pos.this_thread()->history;
- Color c = pos.side_to_move();
+ else if (Type == QUIETS)
+ m.value = (*mainHistory)[pos.side_to_move()][from_to(m)]
+ + (*contHistory[0])[pos.moved_piece(m)][to_sq(m)]
+ + (*contHistory[1])[pos.moved_piece(m)][to_sq(m)]
+ + (*contHistory[3])[pos.moved_piece(m)][to_sq(m)];
- for (auto& m : *this)
- if (pos.capture(m))
- m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
- - Value(type_of(pos.moved_piece(m))) + HistoryStats::Max;
- else
- m.value = history.get(c, m);
+ else // Type == EVASIONS
+ {
+ if (pos.capture(m))
+ m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
+ - Value(type_of(pos.moved_piece(m)));
+ else
+ m.value = (*mainHistory)[pos.side_to_move()][from_to(m)] - (1 << 28);
+ }
}
-
/// next_move() is the most important method of the MovePicker class. It returns
/// a new pseudo legal move every time it is called, until there are no more moves
/// left. It picks the move with the biggest value from a list of generated moves
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:
+ case QSEARCH_RECAPTURES:
endBadCaptures = cur = moves;
endMoves = generate<CAPTURES>(pos, cur);
score<CAPTURES>();
++stage;
+ // Rebranch at the top of the switch via a recursive call
+ return next_move(skipQuiets);
+
case GOOD_CAPTURES:
while (cur < endMoves)
{
move = pick_best(cur++, endMoves);
if (move != ttMove)
{
- if (pos.see_ge(move, VALUE_ZERO))
+ if (pos.see_ge(move, Value(-55 * (cur-1)->value / 1024)))
return move;
// Losing capture, move it to the beginning of the array
}
++stage;
- move = ss->killers[0]; // First killer move
+ 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 = ss->killers[1]; // Second killer move
+ move = killers[1]; // Second killer move
if ( move != MOVE_NONE
&& move != ttMove
&& pos.pseudo_legal(move)
&& !pos.capture(move))
return move;
+ /* fallthrough */
case COUNTERMOVE:
++stage;
move = countermove;
if ( move != MOVE_NONE
&& move != ttMove
- && move != ss->killers[0]
- && move != ss->killers[1]
+ && move != killers[0]
+ && move != killers[1]
&& pos.pseudo_legal(move)
&& !pos.capture(move))
return move;
+ /* fallthrough */
case QUIET_INIT:
cur = endBadCaptures;
endMoves = generate<QUIETS>(pos, cur);
score<QUIETS>();
-
- partial_insertion_sort(cur, endMoves,
- depth < 3 * ONE_PLY ? VALUE_ZERO : Value(INT_MIN));
+ partial_insertion_sort(cur, endMoves, -4000 * depth / ONE_PLY);
++stage;
+ /* fallthrough */
case QUIET:
- while ( cur < endMoves
- && (!skipQuiets || cur->value >= VALUE_ZERO))
- {
- move = *cur++;
-
- if ( move != ttMove
- && move != ss->killers[0]
- && move != ss->killers[1]
- && move != countermove)
- return move;
- }
+ if (!skipQuiets)
+ while (cur < endMoves)
+ {
+ move = *cur++;
+
+ if ( move != ttMove
+ && move != killers[0]
+ && move != killers[1]
+ && move != countermove)
+ return move;
+ }
++stage;
cur = moves; // Point to beginning of bad captures
+ /* fallthrough */
case BAD_CAPTURES:
if (cur < endBadCaptures)
endMoves = generate<EVASIONS>(pos, cur);
score<EVASIONS>();
++stage;
+ /* fallthrough */
case ALL_EVASIONS:
while (cur < endMoves)
}
break;
- case PROBCUT_INIT:
- cur = moves;
- endMoves = generate<CAPTURES>(pos, cur);
- score<CAPTURES>();
- ++stage;
-
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;
-
- case QCAPTURES_1: case QCAPTURES_2:
+ case QCAPTURES:
while (cur < endMoves)
{
move = pick_best(cur++, endMoves);
if (move != ttMove)
return move;
}
- if (stage == QCAPTURES_2)
+ if (depth <= DEPTH_QS_NO_CHECKS)
break;
cur = moves;
endMoves = generate<QUIET_CHECKS>(pos, cur);
++stage;
+ /* fallthrough */
case QCHECKS:
while (cur < endMoves)
}
break;
- case QSEARCH_RECAPTURES:
- cur = moves;
- endMoves = generate<CAPTURES>(pos, cur);
- score<CAPTURES>();
- ++stage;
-
case QRECAPTURES:
while (cur < endMoves)
{
- move = pick_best(cur++, endMoves);
+ move = *cur++;
if (to_sq(move) == recaptureSquare)
return move;
}
projects / stockfish / blobdiff