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Use stat_malus when decreasing stats #4864

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Use stat_malus when decreasing stats #4864

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25 changes: 16 additions & 9 deletions src/search.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,10 @@ constexpr int futility_move_count(bool improving, Depth depth) {
}

// History and stats update bonus, based on depth
int stat_bonus(Depth d) { return std::min(357 * d - 483, 1511); }
int stat_bonus(Depth d) { return std::min(364 * d - 438, 1501); }

// History and stats update malus, based on depth
int stat_malus(Depth d) { return std::min(452 * d - 452, 1478); }

// Add a small random component to draw evaluations to avoid 3-fold blindness
Value value_draw(const Thread* thisThread) {
Expand Down Expand Up @@ -636,12 +639,12 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
// the previous ply (~0 Elo on STC, ~2 Elo on LTC).
if (prevSq != SQ_NONE && (ss - 1)->moveCount <= 2 && !priorCapture)
update_continuation_histories(ss - 1, pos.piece_on(prevSq), prevSq,
-stat_bonus(depth + 1));
-stat_malus(depth + 1));
}
// Penalty for a quiet ttMove that fails low (~1 Elo)
else if (!ttCapture)
{
int penalty = -stat_bonus(depth);
int penalty = -stat_malus(depth);
thisThread->mainHistory[us][from_to(ttMove)] << penalty;
update_continuation_histories(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty);
}
Expand Down Expand Up @@ -1182,7 +1185,7 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
if (newDepth > d)
value = -search<NonPV>(pos, ss + 1, -(alpha + 1), -alpha, newDepth, !cutNode);

int bonus = value <= alpha ? -stat_bonus(newDepth)
int bonus = value <= alpha ? -stat_malus(newDepth)
: value >= beta ? stat_bonus(newDepth)
: 0;

Expand Down Expand Up @@ -1675,6 +1678,7 @@ void update_all_stats(const Position& pos,
PieceType captured;

int quietMoveBonus = stat_bonus(depth + 1);
int quietMoveMalus = stat_malus(depth + 1);

if (!pos.capture_stage(bestMove))
{
Expand All @@ -1686,15 +1690,18 @@ void update_all_stats(const Position& pos,
thisThread->pawnHistory[pawn_structure(pos)][moved_piece][to_sq(bestMove)]
<< quietMoveBonus;

int moveMalus = bestValue > beta + 168 ? quietMoveMalus // larger malus
: stat_malus(depth); // smaller malus

// Decrease stats for all non-best quiet moves
for (int i = 0; i < quietCount; ++i)
{
thisThread->pawnHistory[pawn_structure(pos)][pos.moved_piece(quietsSearched[i])]
[to_sq(quietsSearched[i])]
<< -bestMoveBonus;
thisThread->mainHistory[us][from_to(quietsSearched[i])] << -bestMoveBonus;
<< -moveMalus;
thisThread->mainHistory[us][from_to(quietsSearched[i])] << -moveMalus;
update_continuation_histories(ss, pos.moved_piece(quietsSearched[i]),
to_sq(quietsSearched[i]), -bestMoveBonus);
to_sq(quietsSearched[i]), -moveMalus);
}
}
else
Expand All @@ -1710,14 +1717,14 @@ void update_all_stats(const Position& pos,
&& ((ss - 1)->moveCount == 1 + (ss - 1)->ttHit
|| ((ss - 1)->currentMove == (ss - 1)->killers[0]))
&& !pos.captured_piece())
update_continuation_histories(ss - 1, pos.piece_on(prevSq), prevSq, -quietMoveBonus);
update_continuation_histories(ss - 1, pos.piece_on(prevSq), prevSq, -quietMoveMalus);

// Decrease stats for all non-best capture moves
for (int i = 0; i < captureCount; ++i)
{
moved_piece = pos.moved_piece(capturesSearched[i]);
captured = type_of(pos.piece_on(to_sq(capturesSearched[i])));
captureHistory[moved_piece][to_sq(capturesSearched[i])][captured] << -quietMoveBonus;
captureHistory[moved_piece][to_sq(capturesSearched[i])][captured] << -quietMoveMalus;
}
}

Expand Down