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));
}
// 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 ? 29 : 8 * d * d + 224 * d - 215;
}
// Add a small random component to draw evaluations to avoid 3fold-blindness
tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
}
- // Update static history for previous move
+ // Use static evaluation difference to improve quiet move ordering
if (is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture)
{
- int bonus = ss->staticEval > -(ss-1)->staticEval + 2 * Tempo ? -stat_bonus(depth) :
- ss->staticEval < -(ss-1)->staticEval + 2 * Tempo ? stat_bonus(depth) :
- 0;
- thisThread->staticHistory[~us][from_to((ss-1)->currentMove)] << bonus;
+ 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;
}
- // 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);
-
// 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
? 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
}
}
- probCutBeta = beta + 183 - 49 * improving;
+ probCutBeta = beta + 194 - 49 * 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
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)
Move countermove = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq];
MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
- &thisThread->staticHistory,
&thisThread->lowPlyHistory,
&captureHistory,
contHist,
// Mark this node as being searched
ThreadHolding th(thisThread, posKey, ss->ply);
- // Step 12. Loop through all pseudo-legal moves until no moves remain
+ // Step 11. Loop through all pseudo-legal moves until no moves remain
// or a beta cutoff occurs.
while ((move = mp.next_move(moveCountPruning)) != MOVE_NONE)
{
// Calculate new depth for this move
newDepth = depth - 1;
- // Step 13. Pruning at shallow depth (~200 Elo)
+ // Step 12. Pruning at shallow depth (~200 Elo)
if ( !rootNode
&& pos.non_pawn_material(us)
&& bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
// Futility pruning: parent node (~5 Elo)
if ( lmrDepth < 7
&& !ss->inCheck
- && ss->staticEval + 266 + 170 * lmrDepth <= alpha
+ && ss->staticEval + 254 + 159 * 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)] / 2 < 26394)
continue;
// Prune moves with negative SEE (~20 Elo)
continue;
// SEE based pruning
- if (!pos.see_ge(move, Value(-213) * depth)) // (~25 Elo)
+ if (!pos.see_ge(move, Value(-218) * depth)) // (~25 Elo)
continue;
}
}
- // Step 14. Extensions (~75 Elo)
+ // Step 13. Extensions (~75 Elo)
// Singular extension search (~70 Elo). If all moves but one fail low on a
// search of (alpha-s, beta-s), and just one fails high on (alpha, beta),
&& 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;
[movedPiece]
[to_sq(move)];
- // Step 15. Make the move
+ // Step 14. 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
+ // Step 15. Reduced depth search (LMR, ~200 Elo). If the move fails high it will be
// re-searched at full depth.
if ( depth >= 3
&& moveCount > 1 + 2 * rootNode
|| moveCountPruning
|| ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha
|| cutNode
+ || (!PvNode && !formerPv && thisThread->captureHistory[movedPiece][to_sq(move)][type_of(pos.captured_piece())] < 4506)
|| thisThread->ttHitAverage < 432 * TtHitAverageResolution * TtHitAverageWindow / 1024))
{
Depth r = reduction(improving, depth, moveCount);
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++;
// More reductions for late moves if position was not in previous PV
didLMR = false;
}
- // Step 17. Full depth search when LMR is skipped or fails high
+ // Step 16. Full depth search when LMR is skipped or fails high
if (doFullDepthSearch)
{
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
std::min(maxNextDepth, newDepth), false);
}
- // Step 18. Undo move
+ // Step 17. Undo move
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
- // Step 19. Check for a new best move
+ // Step 18. Check for a new best move
// Finished searching the move. If a stop occurred, the return value of
// the search cannot be trusted, and we return immediately without
// updating best move, PV and TT.
return VALUE_DRAW;
*/
- // Step 20. Check for mate and stalemate
+ // Step 19. Check for mate and stalemate
// All legal moves have been searched and if there are no legal moves, it
// must be a mate or a stalemate. If we are in a singular extension search then
// return a fail low score.
// queen and checking knight promotions, and other checks(only if depth >= DEPTH_QS_CHECKS)
// will be generated.
MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
- &thisThread->staticHistory,
&thisThread->captureHistory,
contHist,
to_sq((ss-1)->currentMove));
projects / stockfish / blobdiff