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clean up code

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**Non functional changes:**
in search.cpp:
- an unnecessary pair of parenthesis in the IIR condition has been removed.
- refactored the stalemate trap detection code

in movepick.cpp:
- use the variables `from`, `to`, `piece`, `pieceType` and `capturedPiece`  instead of calling the same functions multiple times in `MovePicker::score()`.
- rename `MovePicker::other_piece_types_mobile()`.

**Functional changes:**
- make sure the processed move is always legal in `MovePicker::other_piece_types_mobile()`.

passed non regression STC:
https://tests.stockfishchess.org/tests/view/6829da686ec7634154f99faf
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 95680 W: 24962 L: 24820 D: 45898
Ptnml(0-2): 221, 9622, 28025, 9738, 234

Passed non regression LTC:
https://tests.stockfishchess.org/tests/view/682a102c6ec7634154f9a086
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 117666 W: 30065 L: 29957 D: 57644
Ptnml(0-2): 45, 10173, 38291, 10277, 47

Run of 10k games on the stalemate opening book:
https://tests.stockfishchess.org/tests/view/682b114e6ec7634154f9aa2d
Elo: 0.76 ± 0.9 (95%) LOS: 95.3%
Total: 10000 W: 4637 L: 4615 D: 748
Ptnml(0-2): 0, 75, 4828, 97, 0
nElo: 5.83 ± 6.8 (95%) PairsRatio: 1.29

closes https://github.com/official-stockfish/Stockfish/pull/6080

Bench: 2422771
This commit is contained in:
Nonlinear2
2025-05-17 22:50:47 +02:00
committed by Joost VandeVondele
parent 347e328fdb
commit 54fb42ddf8
3 changed files with 44 additions and 54 deletions
Download Patch File Download Diff File Expand all files Collapse all files

57
src/movepick.cpp
View File

@@ -126,11 +126,11 @@ void MovePicker::score() {
static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type");
Color us = pos.side_to_move();
[[maybe_unused]] Bitboard threatenedPieces, threatByLesser[QUEEN + 1];
if constexpr (Type == QUIETS)
{
Color us = pos.side_to_move();
threatByLesser[KNIGHT] = threatByLesser[BISHOP] = pos.attacks_by<PAWN>(~us);
threatByLesser[ROOK] =
pos.attacks_by<KNIGHT>(~us) | pos.attacks_by<BISHOP>(~us) | threatByLesser[KNIGHT];
@@ -143,21 +143,21 @@ void MovePicker::score() {
}
for (auto& m : *this)
{
const Square from = m.from_sq();
const Square to = m.to_sq();
const Piece pc = pos.moved_piece(m);
const PieceType pt = type_of(pc);
const Piece capturedPiece = pos.piece_on(to);
if constexpr (Type == CAPTURES)
m.value =
7 * int(PieceValue[pos.piece_on(m.to_sq())])
+ 1024 * bool(pos.check_squares(type_of(pos.moved_piece(m))) & m.to_sq())
+ (*captureHistory)[pos.moved_piece(m)][m.to_sq()][type_of(pos.piece_on(m.to_sq()))];
m.value = (*captureHistory)[pc][to][type_of(capturedPiece)]
+ 7 * int(PieceValue[capturedPiece]) + 1024 * bool(pos.check_squares(pt) & to);
else if constexpr (Type == QUIETS)
{
Piece pc = pos.moved_piece(m);
PieceType pt = type_of(pc);
Square from = m.from_sq();
Square to = m.to_sq();
// histories
m.value = 2 * (*mainHistory)[pos.side_to_move()][m.from_to()];
m.value = 2 * (*mainHistory)[us][m.from_to()];
m.value += 2 * (*pawnHistory)[pawn_structure_index(pos)][pc][to];
m.value += (*continuationHistory[0])[pc][to];
m.value += (*continuationHistory[1])[pc][to];
@@ -184,15 +184,15 @@ void MovePicker::score() {
else // Type == EVASIONS
{
if (pos.capture_stage(m))
m.value = PieceValue[pos.piece_on(m.to_sq())] + (1 << 28);
m.value = PieceValue[capturedPiece] + (1 << 28);
else
{
m.value = (*mainHistory)[pos.side_to_move()][m.from_to()]
+ (*continuationHistory[0])[pos.moved_piece(m)][m.to_sq()];
m.value = (*mainHistory)[us][m.from_to()] + (*continuationHistory[0])[pc][to];
if (ply < LOW_PLY_HISTORY_SIZE)
m.value += 2 * (*lowPlyHistory)[ply][m.from_to()] / (1 + ply);
}
}
}
}
// Returns the next move satisfying a predicate function.
@@ -221,7 +221,6 @@ top:
case QSEARCH_TT :
case PROBCUT_TT :
++stage;
cur = moves + 1;
return ttMove;
case CAPTURE_INIT :
@@ -237,12 +236,10 @@ top:
case GOOD_CAPTURE :
if (select([&]() {
if (!pos.see_ge(*cur, -cur->value / 18))
{
std::swap(*endBadCaptures++, *cur);
return false;
}
return true;
if (pos.see_ge(*cur, -cur->value / 18))
return true;
std::swap(*endBadCaptures++, *cur);
return false;
}))
return *(cur - 1);
@@ -315,23 +312,17 @@ top:
void MovePicker::skip_quiet_moves() { skipQuiets = true; }
bool MovePicker::other_piece_types_mobile(PieceType pt) {
// this function must be called after all quiet moves and captures have been generated
bool MovePicker::can_move_king_or_pawn() {
assert(stage == GOOD_QUIET || stage == BAD_QUIET || stage == EVASION);
// verify all generated captures and quiets
for (ExtMove* m = moves; m < endMoves; ++m)
{
if (*m && type_of(pos.moved_piece(*m)) != pt)
{
if (type_of(pos.moved_piece(*m)) != KING)
return true;
if (pos.legal(*m))
return true;
}
PieceType movedPieceType = type_of(pos.moved_piece(*m));
if ((movedPieceType == PAWN || movedPieceType == KING) && pos.legal(*m))
return true;
}
return false;
}
void MovePicker::mark_current_illegal() { *(cur - 1) = Move::none(); }
} // namespace Stockfish

3
src/movepick.h
View File

@@ -50,8 +50,7 @@ class MovePicker {
MovePicker(const Position&, Move, int, const CapturePieceToHistory*);
Move next_move();
void skip_quiet_moves();
bool other_piece_types_mobile(PieceType pt);
void mark_current_illegal();
bool can_move_king_or_pawn();
private:
template<typename Pred>

38
src/search.cpp
View File

@@ -910,7 +910,7 @@ Value Search::Worker::search(
// Step 10. Internal iterative reductions
// For PV nodes without a ttMove as well as for deep enough cutNodes, we decrease depth.
// (*Scaler) Especially if they make IIR less aggressive.
if ((!allNode && depth >= (PvNode ? 5 : 7)) && !ttData.move)
if (!allNode && depth >= (PvNode ? 5 : 7) && !ttData.move)
depth--;
// Step 11. ProbCut
@@ -1002,10 +1002,8 @@ moves_loop: // When in check, search starts here
// Check for legality
if (!pos.legal(move))
{
mp.mark_current_illegal();
continue;
}
// At root obey the "searchmoves" option and skip moves not listed in Root
// Move List. In MultiPV mode we also skip PV moves that have been already
// searched and those of lower "TB rank" if we are in a TB root position.
@@ -1074,15 +1072,17 @@ moves_loop: // When in check, search starts here
int seeHist = std::clamp(captHist / 31, -137 * depth, 125 * depth);
if (!pos.see_ge(move, -158 * depth - seeHist))
{
bool skip = true;
if (depth > 2 && !capture && givesCheck && alpha < 0
&& pos.non_pawn_material(us) == PieceValue[movedPiece]
&& PieceValue[movedPiece] >= RookValue
&& !(PseudoAttacks[KING][pos.square<KING>(us)] & move.from_sq()))
// if the opponent captures last mobile piece it might be stalemate
skip = mp.other_piece_types_mobile(type_of(movedPiece));
bool mayStalemateTrap =
depth > 2 && givesCheck && alpha < 0
&& !capture // we consider that captures will likely destroy the stalemate configuration
&& pos.non_pawn_material(us) == PieceValue[movedPiece]
&& PieceValue[movedPiece] >= RookValue
// it can't be stalemate if we moved a piece adjacent to the king
&& !(attacks_bb<KING>(pos.square<KING>(us)) & move.from_sq())
&& !mp.can_move_king_or_pawn();
if (skip)
// avoid pruning sacrifices of our last piece for stalemate
if (!mayStalemateTrap)
continue;
}
}
@@ -1873,8 +1873,8 @@ void update_all_stats(const Position& pos,
int moveCount) {
CapturePieceToHistory& captureHistory = workerThread.captureHistory;
Piece moved_piece = pos.moved_piece(bestMove);
PieceType captured;
Piece movedPiece = pos.moved_piece(bestMove);
PieceType capturedPiece;
int bonus = std::min(143 * depth - 89, 1496) + 302 * (bestMove == ttMove);
int malus = std::min(737 * depth - 179, 3141) - 30 * moveCount;
@@ -1890,8 +1890,8 @@ void update_all_stats(const Position& pos,
else
{
// Increase stats for the best move in case it was a capture move
captured = type_of(pos.piece_on(bestMove.to_sq()));
captureHistory[moved_piece][bestMove.to_sq()][captured] << bonus * 1213 / 1024;
capturedPiece = type_of(pos.piece_on(bestMove.to_sq()));
captureHistory[movedPiece][bestMove.to_sq()][capturedPiece] << bonus * 1213 / 1024;
}
// Extra penalty for a quiet early move that was not a TT move in
@@ -1902,9 +1902,9 @@ void update_all_stats(const Position& pos,
// Decrease stats for all non-best capture moves
for (Move move : capturesSearched)
{
moved_piece = pos.moved_piece(move);
captured = type_of(pos.piece_on(move.to_sq()));
captureHistory[moved_piece][move.to_sq()][captured] << -malus * 1388 / 1024;
movedPiece = pos.moved_piece(move);
capturedPiece = type_of(pos.piece_on(move.to_sq()));
captureHistory[movedPiece][move.to_sq()][capturedPiece] << -malus * 1388 / 1024;
}
}