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
QSEARCH_RECAPTURES, QRECAPTURES
};
- // Our insertion sort, which is guaranteed to be stable, as it should be
- void insertion_sort(ExtMove* begin, ExtMove* end)
+ // 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, int limit)
{
- 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;
- }
+ for (ExtMove *sortedEnd = begin + 1, *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;
+ ++sortedEnd;
+ }
}
// pick_best() finds the best move in the range (begin, end) and moves it to
stage = PROBCUT;
- // In ProbCut we generate captures with SEE higher than the given threshold
+ // 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(ttm) > threshold ? ttm : MOVE_NONE;
+ && pos.see_ge(ttm, threshold)? ttm : MOVE_NONE;
stage += (ttMove == MOVE_NONE);
}
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;
+ const CounterMoveStats& cmh = *(ss-1)->counterMoves;
+ const CounterMoveStats& fmh = *(ss-2)->counterMoves;
+ const CounterMoveStats& fm2 = *(ss-4)->counterMoves;
Color c = pos.side_to_move();
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);
+ 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);
}
template<>
void MovePicker::score<EVASIONS>() {
- // Try winning and equal captures ordered by MVV/LVA, then non-captures ordered
- // by history value, then bad captures and quiet moves with a negative SEE ordered
- // by SEE value.
+ // Try captures ordered by MVV/LVA, then non-captures ordered by stats heuristics
const HistoryStats& history = pos.this_thread()->history;
- const FromToStats& fromTo = pos.this_thread()->fromTo;
Color c = pos.side_to_move();
- Value see;
for (auto& m : *this)
- if ((see = pos.see_sign(m)) < VALUE_ZERO)
- m.value = see - HistoryStats::Max; // At the bottom
-
- else if (pos.capture(m))
+ 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);
+ m.value = history.get(c, m);
}
/// 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;
move = pick_best(cur++, endMoves);
if (move != ttMove)
{
- if (pos.see_sign(move) >= VALUE_ZERO)
+ if (pos.see_ge(move, VALUE_ZERO))
return move;
// Losing capture, move it to the beginning of the array
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,
+ depth < 3 * ONE_PLY ? 0 : INT_MIN);
++stage;
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]
case EVASIONS_INIT:
cur = moves;
endMoves = generate<EVASIONS>(pos, cur);
- if (endMoves - cur - (ttMove != MOVE_NONE) > 1)
- score<EVASIONS>();
+ score<EVASIONS>();
++stage;
case ALL_EVASIONS:
{
move = pick_best(cur++, endMoves);
if ( move != ttMove
- && pos.see(move) > threshold)
+ && pos.see_ge(move, threshold))
return move;
}
break;
projects / stockfish / blobdiff