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) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2017 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 {
QSEARCH_RECAPTURES, QRECAPTURES
};
- // Our insertion sort, which is guaranteed to be stable, as it should be
- void insertion_sort(ExtMove* begin, ExtMove* end)
- {
- ExtMove tmp, *p, *q;
-
- for (p = begin + 1; p < end; ++p)
- {
- tmp = *p;
- for (q = p; q != begin && *(q-1) < tmp; --q)
- *q = *(q-1);
- *q = tmp;
- }
+ // 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);
+ *q = tmp;
+ }
}
// 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) {
assert(d <= DEPTH_ZERO);
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 the given threshold
ttMove = ttm
&& pos.pseudo_legal(ttm)
&& pos.capture(ttm)
- && pos.see(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 FromToStats& fromTo = pos.this_thread()->fromTo;
-
- const CounterMoveStats* cm = (ss-1)->counterMoves;
- const CounterMoveStats* fm = (ss-2)->counterMoves;
- const CounterMoveStats* f2 = (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 = history[pos.moved_piece(m)][to_sq(m)]
- + (cm ? (*cm)[pos.moved_piece(m)][to_sq(m)] : VALUE_ZERO)
- + (fm ? (*fm)[pos.moved_piece(m)][to_sq(m)] : VALUE_ZERO)
- + (f2 ? (*f2)[pos.moved_piece(m)][to_sq(m)] : VALUE_ZERO)
- + fromTo.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 history value
- const HistoryStats& history = pos.this_thread()->history;
- const FromToStats& fromTo = pos.this_thread()->fromTo;
- 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[pos.moved_piece(m)][to_sq(m)] + fromTo.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
/// taking care not to return the ttMove if it has already been searched.
-Move MovePicker::next_move() {
+Move MovePicker::next_move(bool skipQuiets) {
Move move;
endMoves = generate<CAPTURES>(pos, cur);
score<CAPTURES>();
++stage;
+ /* fallthrough */
case GOOD_CAPTURES:
while (cur < endMoves)
move = pick_best(cur++, endMoves);
if (move != ttMove)
{
- if (pos.see_sign(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>();
- if (depth < 3 * ONE_PLY)
- {
- ExtMove* goodQuiet = std::partition(cur, endMoves, [](const ExtMove& m)
- { return m.value > VALUE_ZERO; });
- insertion_sort(cur, goodQuiet);
- } else
- insertion_sort(cur, endMoves);
+ partial_insertion_sort(cur, endMoves, -4000 * depth / ONE_PLY);
++stage;
+ /* fallthrough */
case QUIET:
- while (cur < endMoves)
+ while ( cur < endMoves
+ && (!skipQuiets || cur->value >= VALUE_ZERO))
{
move = *cur++;
+
if ( move != ttMove
- && move != ss->killers[0]
- && move != ss->killers[1]
+ && 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)
case EVASIONS_INIT:
cur = moves;
endMoves = generate<EVASIONS>(pos, cur);
- if (endMoves - cur - (ttMove != MOVE_NONE) > 1)
- score<EVASIONS>();
+ score<EVASIONS>();
++stage;
+ /* fallthrough */
case ALL_EVASIONS:
while (cur < endMoves)
endMoves = generate<CAPTURES>(pos, cur);
score<CAPTURES>();
++stage;
+ /* fallthrough */
case PROBCUT_CAPTURES:
while (cur < endMoves)
{
move = pick_best(cur++, endMoves);
if ( move != ttMove
- && pos.see(move) > threshold)
+ && pos.see_ge(move, threshold))
return move;
}
break;
endMoves = generate<CAPTURES>(pos, cur);
score<CAPTURES>();
++stage;
+ /* fallthrough */
case QCAPTURES_1: case QCAPTURES_2:
while (cur < endMoves)
cur = moves;
endMoves = generate<QUIET_CHECKS>(pos, cur);
++stage;
+ /* fallthrough */
case QCHECKS:
while (cur < endMoves)
endMoves = generate<CAPTURES>(pos, cur);
score<CAPTURES>();
++stage;
+ /* fallthrough */
case QRECAPTURES:
while (cur < endMoves)
projects / stockfish / blobdiff