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Merge remote-tracking branch 'upstream/master' into data_generation

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This commit is contained in:
Tomasz Sobczyk
2021-04-18 19:45:46 +02:00
parent f1d4c1c896 a7ab92ec25
commit 08e255960d
61 changed files with 1444 additions and 1577 deletions
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252
src/search.cpp
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@@ -1,6 +1,6 @@
/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2020 The Stockfish developers (see AUTHORS file)
Copyright (C) 2004-2021 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
@@ -37,6 +37,8 @@
#include "uci.h"
#include "syzygy/tbprobe.h"
namespace Stockfish {
namespace Search {
LimitsType Limits;
@@ -56,8 +58,7 @@ namespace {
constexpr uint64_t TtHitAverageWindow = 4096;
constexpr uint64_t TtHitAverageResolution = 1024;
// Razor and futility margins
constexpr int RazorMargin = 510;
// Futility margin
Value futility_margin(Depth d, bool improving) {
return Value(234 * (d - improving));
}
@@ -76,10 +77,10 @@ namespace {
// History and stats update bonus, based on depth
int stat_bonus(Depth d) {
return d > 13 ? 29 : 17 * d * d + 134 * d - 134;
return d > 14 ? 66 : 6 * d * d + 231 * d - 206;
}
// Add a small random component to draw evaluations to avoid 3fold-blindness
// Add a small random component to draw evaluations to avoid 3-fold blindness
Value value_draw(Thread* thisThread) {
return VALUE_DRAW + Value(2 * (thisThread->nodes & 1) - 1);
}
@@ -420,7 +421,7 @@ void Thread::search() {
while (true)
{
Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt - searchAgainCounter);
bestValue = ::search<PV>(rootPos, ss, alpha, beta, adjustedDepth, false);
bestValue = Stockfish::search<PV>(rootPos, ss, alpha, beta, adjustedDepth, false);
// Bring the best move to the front. It is critical that sorting
// is done with a stable algorithm because all the values but the
@@ -608,12 +609,12 @@ namespace {
// Step 1. Initialize node
Thread* thisThread = pos.this_thread();
ss->inCheck = pos.checkers();
priorCapture = pos.captured_piece();
Color us = pos.side_to_move();
moveCount = captureCount = quietCount = ss->moveCount = 0;
bestValue = -VALUE_INFINITE;
maxValue = VALUE_INFINITE;
ss->inCheck = pos.checkers();
priorCapture = pos.captured_piece();
Color us = pos.side_to_move();
moveCount = captureCount = quietCount = ss->moveCount = 0;
bestValue = -VALUE_INFINITE;
maxValue = VALUE_INFINITE;
// Check for the available remaining time
if (thisThread == Threads.main())
@@ -673,6 +674,7 @@ namespace {
ss->ttPv = PvNode || (ss->ttHit && tte->is_pv());
formerPv = ss->ttPv && !PvNode;
// Update low ply history for previous move if we are near root and position is or has been in PV
if ( ss->ttPv
&& depth > 12
&& ss->ply - 1 < MAX_LPH
@@ -697,6 +699,7 @@ namespace {
{
if (ttValue >= beta)
{
// Bonus for a quiet ttMove that fails high
if (!pos.capture_or_promotion(ttMove))
update_quiet_stats(pos, ss, ttMove, stat_bonus(depth), depth);
@@ -713,6 +716,8 @@ namespace {
}
}
// Partial workaround for the graph history interaction problem
// For high rule50 counts don't produce transposition table cutoffs.
if (pos.rule50_count() < 90)
return ttValue;
}
@@ -786,6 +791,7 @@ namespace {
if (eval == VALUE_NONE)
ss->staticEval = eval = evaluate(pos);
// Randomize draw evaluation
if (eval == VALUE_DRAW)
eval = value_draw(thisThread);
@@ -796,38 +802,46 @@ namespace {
}
else
{
// In case of null move search use previous static eval with a different sign
// and addition of two tempos
if ((ss-1)->currentMove != MOVE_NULL)
ss->staticEval = eval = evaluate(pos);
else
ss->staticEval = eval = -(ss-1)->staticEval + 2 * Tempo;
// Save static evaluation into transposition table
tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
}
// Step 7. Razoring (~1 Elo)
if ( !rootNode // The required rootNode PV handling is not available in qsearch
&& depth == 1
&& eval <= alpha - RazorMargin)
return qsearch<NT>(pos, ss, alpha, beta);
// Use static evaluation difference to improve quiet move ordering
if (is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture)
{
int bonus = std::clamp(-depth * 4 * int((ss-1)->staticEval + ss->staticEval - 2 * Tempo), -1000, 1000);
thisThread->mainHistory[~us][from_to((ss-1)->currentMove)] << bonus;
}
// Set up improving flag that is used in various pruning heuristics
// We define position as improving if static evaluation of position is better
// Than the previous static evaluation at our turn
// In case of us being in check at our previous move we look at move prior to it
improving = (ss-2)->staticEval == VALUE_NONE
? ss->staticEval > (ss-4)->staticEval || (ss-4)->staticEval == VALUE_NONE
: ss->staticEval > (ss-2)->staticEval;
// Step 8. Futility pruning: child node (~50 Elo)
// Step 7. Futility pruning: child node (~50 Elo)
if ( !PvNode
&& depth < 8
&& depth < 9
&& eval - futility_margin(depth, improving) >= beta
&& eval < VALUE_KNOWN_WIN) // Do not return unproven wins
return eval;
// Step 9. Null move search with verification search (~40 Elo)
// Step 8. Null move search with verification search (~40 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
&& (ss-1)->statScore < 22977
&& (ss-1)->statScore < 24185
&& eval >= beta
&& eval >= ss->staticEval
&& ss->staticEval >= beta - 30 * depth - 28 * improving + 84 * ss->ttPv + 168
&& ss->staticEval >= beta - 24 * depth - 34 * improving + 162 * ss->ttPv + 159
&& !excludedMove
&& pos.non_pawn_material(us)
&& (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
@@ -835,7 +849,7 @@ namespace {
assert(eval - beta >= 0);
// Null move dynamic reduction based on depth and value
Depth R = (1015 + 85 * depth) / 256 + std::min(int(eval - beta) / 191, 3);
Depth R = (1062 + 68 * depth) / 256 + std::min(int(eval - beta) / 190, 3);
ss->currentMove = MOVE_NULL;
ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0];
@@ -871,9 +885,9 @@ namespace {
}
}
probCutBeta = beta + 183 - 49 * improving;
probCutBeta = beta + 209 - 44 * improving;
// Step 10. ProbCut (~10 Elo)
// Step 9. ProbCut (~10 Elo)
// If we have a good enough capture and a reduced search returns a value
// much above beta, we can (almost) safely prune the previous move.
if ( !PvNode
@@ -899,6 +913,7 @@ namespace {
return probCutBeta;
assert(probCutBeta < VALUE_INFINITE);
MovePicker mp(pos, ttMove, probCutBeta - ss->staticEval, &captureHistory);
int probCutCount = 0;
bool ttPv = ss->ttPv;
@@ -946,7 +961,7 @@ namespace {
ss->ttPv = ttPv;
}
// Step 11. If the position is not in TT, decrease depth by 2
// Step 10. If the position is not in TT, decrease depth by 2
if ( PvNode
&& depth >= 6
&& !ttMove)
@@ -954,6 +969,23 @@ namespace {
moves_loop: // When in check, search starts from here
ttCapture = ttMove && pos.capture_or_promotion(ttMove);
// Step 11. A small Probcut idea, when we are in check
probCutBeta = beta + 400;
if ( ss->inCheck
&& !PvNode
&& depth >= 4
&& ttCapture
&& (tte->bound() & BOUND_LOWER)
&& tte->depth() >= depth - 3
&& ttValue >= probCutBeta
&& abs(ttValue) <= VALUE_KNOWN_WIN
&& abs(beta) <= VALUE_KNOWN_WIN
)
return probCutBeta;
const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
nullptr , (ss-4)->continuationHistory,
nullptr , (ss-6)->continuationHistory };
@@ -970,7 +1002,6 @@ moves_loop: // When in check, search starts from here
value = bestValue;
singularQuietLMR = moveCountPruning = false;
ttCapture = ttMove && pos.capture_or_promotion(ttMove);
// Mark this node as being searched
ThreadHolding th(thisThread, posKey, ss->ply);
@@ -1012,6 +1043,14 @@ moves_loop: // When in check, search starts from here
movedPiece = pos.moved_piece(move);
givesCheck = pos.gives_check(move);
// Indicate PvNodes that will probably fail low if node was searched with non-PV search
// at depth equal or greater to current depth and result of this search was far below alpha
bool likelyFailLow = PvNode
&& ttMove
&& (tte->bound() & BOUND_UPPER)
&& ttValue < alpha + 200 + 100 * depth
&& tte->depth() >= depth;
// Calculate new depth for this move
newDepth = depth - 1;
@@ -1027,8 +1066,20 @@ moves_loop: // When in check, search starts from here
// Reduced depth of the next LMR search
int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), 0);
if ( !captureOrPromotion
&& !givesCheck)
if ( captureOrPromotion
|| givesCheck)
{
// Capture history based pruning when the move doesn't give check
if ( !givesCheck
&& lmrDepth < 1
&& captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] < 0)
continue;
// SEE based pruning
if (!pos.see_ge(move, Value(-218) * depth)) // (~25 Elo)
continue;
}
else
{
// Countermoves based pruning (~20 Elo)
if ( lmrDepth < 4 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1)
@@ -1039,29 +1090,17 @@ moves_loop: // When in check, search starts from here
// Futility pruning: parent node (~5 Elo)
if ( lmrDepth < 7
&& !ss->inCheck
&& ss->staticEval + 266 + 170 * lmrDepth <= alpha
&& ss->staticEval + 174 + 157 * lmrDepth <= alpha
&& (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)]
+ (*contHist[5])[movedPiece][to_sq(move)] / 2 < 27376)
+ (*contHist[5])[movedPiece][to_sq(move)] / 3 < 28255)
continue;
// Prune moves with negative SEE (~20 Elo)
if (!pos.see_ge(move, Value(-(30 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth)))
continue;
}
else
{
// Capture history based pruning when the move doesn't give check
if ( !givesCheck
&& lmrDepth < 1
&& captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] < 0)
continue;
// SEE based pruning
if (!pos.see_ge(move, Value(-213) * depth)) // (~25 Elo)
continue;
}
}
// Step 14. Extensions (~75 Elo)
@@ -1082,6 +1121,7 @@ moves_loop: // When in check, search starts from here
{
Value singularBeta = ttValue - ((formerPv + 4) * depth) / 2;
Depth singularDepth = (depth - 1 + 3 * formerPv) / 2;
ss->excludedMove = move;
value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, singularDepth, cutNode);
ss->excludedMove = MOVE_NONE;
@@ -1115,20 +1155,9 @@ moves_loop: // When in check, search starts from here
// Check extension (~2 Elo)
else if ( givesCheck
&& (pos.is_discovery_check_on_king(~us, move) || pos.see_ge(move)))
&& (pos.is_discovered_check_on_king(~us, move) || pos.see_ge(move)))
extension = 1;
// Last captures extension
else if ( PieceValue[EG][pos.captured_piece()] > PawnValueEg
&& pos.non_pawn_material() <= 2 * RookValueMg)
extension = 1;
// Late irreversible move extension
if ( move == ttMove
&& pos.rule50_count() > 80
&& (captureOrPromotion || type_of(movedPiece) == PAWN))
extension = 2;
// Add extension to new depth
newDepth += extension;
@@ -1145,14 +1174,17 @@ moves_loop: // When in check, search starts from here
// Step 15. Make the move
pos.do_move(move, st, givesCheck);
// Step 16. Reduced depth search (LMR, ~200 Elo). If the move fails high it will be
// re-searched at full depth.
// Step 16. Late moves reduction / extension (LMR, ~200 Elo)
// We use various heuristics for the sons of a node after the first son has
// been searched. In general we would like to reduce them, but there are many
// cases where we extend a son if it has good chances to be "interesting".
if ( depth >= 3
&& moveCount > 1 + 2 * rootNode
&& ( !captureOrPromotion
|| moveCountPruning
|| ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha
|| cutNode
|| (!PvNode && !formerPv && captureHistory[movedPiece][to_sq(move)][type_of(pos.captured_piece())] < 3678)
|| thisThread->ttHitAverage < 432 * TtHitAverageResolution * TtHitAverageWindow / 1024))
{
Depth r = reduction(improving, depth, moveCount);
@@ -1165,15 +1197,21 @@ moves_loop: // When in check, search starts from here
if (th.marked())
r++;
// Decrease reduction if position is or has been on the PV (~10 Elo)
if (ss->ttPv)
// Decrease reduction if position is or has been on the PV
// and node is not likely to fail low. (~10 Elo)
if ( ss->ttPv
&& !likelyFailLow)
r -= 2;
// Increase reduction at root and non-PV nodes when the best move does not change frequently
if ((rootNode || !PvNode) && depth > 10 && thisThread->bestMoveChanges <= 2)
if ( (rootNode || !PvNode)
&& thisThread->rootDepth > 10
&& thisThread->bestMoveChanges <= 2)
r++;
if (moveCountPruning && !formerPv)
// More reductions for late moves if position was not in previous PV
if ( moveCountPruning
&& !formerPv)
r++;
// Decrease reduction if opponent's move count is high (~5 Elo)
@@ -1184,7 +1222,14 @@ moves_loop: // When in check, search starts from here
if (singularQuietLMR)
r--;
if (!captureOrPromotion)
if (captureOrPromotion)
{
// Increase reduction for non-checking captures likely to be bad
if ( !givesCheck
&& ss->staticEval + PieceValue[EG][pos.captured_piece()] + 210 * depth <= alpha)
r++;
}
else
{
// Increase reduction if ttMove is a capture (~5 Elo)
if (ttCapture)
@@ -1199,7 +1244,7 @@ moves_loop: // When in check, search starts from here
// Decrease reduction for moves that escape a capture. Filter out
// castling moves, because they are coded as "king captures rook" and
// hence break make_move(). (~2 Elo)
// hence break reverse_move() (~2 Elo)
else if ( type_of(move) == NORMAL
&& !pos.see_ge(reverse_move(move)))
r -= 2 + ss->ttPv - (type_of(movedPiece) == PAWN);
@@ -1208,42 +1253,39 @@ moves_loop: // When in check, search starts from here
+ (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)]
- 5287;
- 4741;
// Decrease/increase reduction by comparing opponent's stat score (~10 Elo)
if (ss->statScore >= -105 && (ss-1)->statScore < -103)
if (ss->statScore >= -89 && (ss-1)->statScore < -116)
r--;
else if ((ss-1)->statScore >= -122 && ss->statScore < -129)
else if ((ss-1)->statScore >= -112 && ss->statScore < -100)
r++;
// Decrease/increase reduction for moves with a good/bad history (~30 Elo)
r -= ss->statScore / 14884;
}
else
{
// Increase reduction for captures/promotions if late move and at low depth
if (depth < 8 && moveCount > 2)
r++;
// Unless giving check, this capture is likely bad
if ( !givesCheck
&& ss->staticEval + PieceValue[EG][pos.captured_piece()] + 210 * depth <= alpha)
r++;
// If we are not in check use statScore, but if we are in check we use
// the sum of main history and first continuation history with an offset.
if (ss->inCheck)
r -= (thisThread->mainHistory[us][from_to(move)]
+ (*contHist[0])[movedPiece][to_sq(move)] - 3833) / 16384;
else
r -= ss->statScore / 14790;
}
Depth d = std::clamp(newDepth - r, 1, newDepth);
// In general we want to cap the LMR depth search at newDepth. But if
// reductions are really negative and movecount is low, we allow this move
// to be searched deeper than the first move.
Depth d = std::clamp(newDepth - r, 1, newDepth + (r < -1 && moveCount <= 5));
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
doFullDepthSearch = value > alpha && d != newDepth;
// If the son is reduced and fails high it will be re-searched at full depth
doFullDepthSearch = value > alpha && d < newDepth;
didLMR = true;
}
else
{
doFullDepthSearch = !PvNode || moveCount > 1;
didLMR = false;
}
@@ -1252,14 +1294,12 @@ moves_loop: // When in check, search starts from here
{
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
// If the move passed LMR update its stats
if (didLMR && !captureOrPromotion)
{
int bonus = value > alpha ? stat_bonus(newDepth)
: -stat_bonus(newDepth);
if (move == ss->killers[0])
bonus += bonus / 4;
update_continuation_histories(ss, movedPiece, to_sq(move), bonus);
}
}
@@ -1306,8 +1346,7 @@ moves_loop: // When in check, search starts from here
rm.pv.push_back(*m);
// We record how often the best move has been changed in each
// iteration. This information is used for time management: when
// the best move changes frequently, we allocate some more time.
// iteration. This information is used for time management and LMR
if (moveCount > 1)
++thisThread->bestMoveChanges;
}
@@ -1340,6 +1379,7 @@ moves_loop: // When in check, search starts from here
}
}
// If the move is worse than some previously searched move, remember it to update its stats later
if (move != bestMove)
{
if (captureOrPromotion && captureCount < 32)
@@ -1366,9 +1406,11 @@ moves_loop: // When in check, search starts from here
assert(moveCount || !ss->inCheck || excludedMove || !MoveList<LEGAL>(pos).size());
if (!moveCount)
bestValue = excludedMove ? alpha
: ss->inCheck ? mated_in(ss->ply) : VALUE_DRAW;
bestValue = excludedMove ? alpha :
ss->inCheck ? mated_in(ss->ply)
: VALUE_DRAW;
// If there is a move which produces search value greater than alpha we update stats of searched moves
else if (bestMove)
update_all_stats(pos, ss, bestMove, bestValue, beta, prevSq,
quietsSearched, quietCount, capturesSearched, captureCount, depth);
@@ -1390,6 +1432,7 @@ moves_loop: // When in check, search starts from here
else if (depth > 3)
ss->ttPv = ss->ttPv && (ss+1)->ttPv;
// Write gathered information in transposition table
if (!excludedMove && !(rootNode && thisThread->pvIdx))
tte->save(posKey, value_to_tt(bestValue, ss->ply), ss->ttPv,
bestValue >= beta ? BOUND_LOWER :
@@ -1485,6 +1528,8 @@ moves_loop: // When in check, search starts from here
bestValue = ttValue;
}
else
// In case of null move search use previous static eval with a different sign
// and addition of two tempos
ss->staticEval = bestValue =
(ss-1)->currentMove != MOVE_NULL ? evaluate(pos)
: -(ss-1)->staticEval + 2 * Tempo;
@@ -1492,6 +1537,7 @@ moves_loop: // When in check, search starts from here
// Stand pat. Return immediately if static value is at least beta
if (bestValue >= beta)
{
// Save gathered info in transposition table
if (!ss->ttHit)
tte->save(posKey, value_to_tt(bestValue, ss->ply), false, BOUND_LOWER,
DEPTH_NONE, MOVE_NONE, ss->staticEval);
@@ -1528,15 +1574,13 @@ moves_loop: // When in check, search starts from here
moveCount++;
// Futility pruning
// Futility pruning and moveCount pruning
if ( bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& !givesCheck
&& futilityBase > -VALUE_KNOWN_WIN
&& !pos.advanced_pawn_push(move))
&& type_of(move) != PROMOTION)
{
assert(type_of(move) != ENPASSANT); // Due to !pos.advanced_pawn_push
// moveCount pruning
if (moveCount > 2)
continue;
@@ -1557,7 +1601,6 @@ moves_loop: // When in check, search starts from here
// Do not search moves with negative SEE values
if ( bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& !(givesCheck && pos.is_discovery_check_on_king(~pos.side_to_move(), move))
&& !pos.see_ge(move))
continue;
@@ -1620,6 +1663,7 @@ moves_loop: // When in check, search starts from here
return mated_in(ss->ply); // Plies to mate from the root
}
// Save gathered info in transposition table
tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit,
bestValue >= beta ? BOUND_LOWER :
PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER,
@@ -1698,14 +1742,15 @@ moves_loop: // When in check, search starts from here
PieceType captured = type_of(pos.piece_on(to_sq(bestMove)));
bonus1 = stat_bonus(depth + 1);
bonus2 = bestValue > beta + PawnValueMg ? bonus1 // larger bonus
: stat_bonus(depth); // smaller bonus
bonus2 = bestValue > beta + PawnValueMg ? bonus1 // larger bonus
: std::min(bonus1, stat_bonus(depth)); // smaller bonus
if (!pos.capture_or_promotion(bestMove))
{
// Increase stats for the best move in case it was a quiet move
update_quiet_stats(pos, ss, bestMove, bonus2, depth);
// Decrease all the non-best quiet moves
// Decrease stats for all non-best quiet moves
for (int i = 0; i < quietCount; ++i)
{
thisThread->mainHistory[us][from_to(quietsSearched[i])] << -bonus2;
@@ -1713,14 +1758,16 @@ moves_loop: // When in check, search starts from here
}
}
else
// Increase stats for the best move in case it was a capture move
captureHistory[moved_piece][to_sq(bestMove)][captured] << bonus1;
// Extra penalty for a quiet early move that was not a TT move or main killer move in previous ply when it gets refuted
// Extra penalty for a quiet early move that was not a TT move or
// main killer move in previous ply when it gets refuted.
if ( ((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, -bonus1);
// Decrease all the non-best capture moves
// Decrease stats for all non-best capture moves
for (int i = 0; i < captureCount; ++i)
{
moved_piece = pos.moved_piece(capturesSearched[i]);
@@ -1737,6 +1784,7 @@ moves_loop: // When in check, search starts from here
for (int i : {1, 2, 4, 6})
{
// Only update first 2 continuation histories if we are in check
if (ss->inCheck && i > 2)
break;
if (is_ok((ss-i)->currentMove))
@@ -1749,6 +1797,7 @@ moves_loop: // When in check, search starts from here
void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus, int depth) {
// Update killers
if (ss->killers[0] != move)
{
ss->killers[1] = ss->killers[0];
@@ -1760,15 +1809,18 @@ moves_loop: // When in check, search starts from here
thisThread->mainHistory[us][from_to(move)] << bonus;
update_continuation_histories(ss, pos.moved_piece(move), to_sq(move), bonus);
// Penalty for reversed move in case of moved piece not being a pawn
if (type_of(pos.moved_piece(move)) != PAWN)
thisThread->mainHistory[us][from_to(reverse_move(move))] << -bonus;
// Update countermove history
if (is_ok((ss-1)->currentMove))
{
Square prevSq = to_sq((ss-1)->currentMove);
thisThread->counterMoves[pos.piece_on(prevSq)][prevSq] = move;
}
// Update low ply history
if (depth > 11 && ss->ply < MAX_LPH)
thisThread->lowPlyHistory[ss->ply][from_to(move)] << stat_bonus(depth - 7);
}
@@ -2249,3 +2301,5 @@ namespace Search
}
}
} // namespace Stockfish