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Parameter Tweaks
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This patch is a parameter tweak that passed both STC and LTC tests.

STC:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 80944 W: 21557 L: 21189 D: 38198
Ptnml(0-2): 192, 8883, 22028, 9103, 266
https://tests.stockfishchess.org/tests/view/63b07fe2d421d8f75795a03b

LTC:
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 30440 W: 8296 L: 8007 D: 14137
Ptnml(0-2): 6, 2893, 9143, 3162, 16
https://tests.stockfishchess.org/tests/view/63b167d02ab1290f961644db

closes #4318

Bench: 4182223
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@FauziAkram @vondele
FauziAkram authored and vondele committed Jan 2, 2023
1 parent a6fa683 commit fc5b59b
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Showing 2 changed files with 36 additions and 36 deletions.
12 changes: 6 additions & 6 deletions src/evaluate.cpp
View file
Expand Up @@ -1056,7 +1056,7 @@ Value Eval::evaluate(const Position& pos, int* complexity) {
// We use the much less accurate but faster Classical eval when the NNUE
// option is set to false. Otherwise we use the NNUE eval unless the
// PSQ advantage is decisive and several pieces remain. (~3 Elo)
bool useClassical = !useNNUE || (pos.count<ALL_PIECES>() > 7 && abs(psq) > 1760);
bool useClassical = !useNNUE || (pos.count<ALL_PIECES>() > 7 && abs(psq) > 1781);

if (useClassical)
v = Evaluation<NO_TRACE>(pos).value();
Expand All @@ -1071,21 +1071,21 @@ Value Eval::evaluate(const Position& pos, int* complexity) {
Value nnue = NNUE::evaluate(pos, true, &nnueComplexity);

// Blend nnue complexity with (semi)classical complexity
nnueComplexity = ( 412 * nnueComplexity
+ 428 * abs(psq - nnue)
nnueComplexity = ( 406 * nnueComplexity
+ 424 * abs(psq - nnue)
+ (optimism > 0 ? int(optimism) * int(psq - nnue) : 0)
) / 1024;

// Return hybrid NNUE complexity to caller
if (complexity)
*complexity = nnueComplexity;

optimism = optimism * (278 + nnueComplexity) / 256;
v = (nnue * scale + optimism * (scale - 755)) / 1024;
optimism = optimism * (272 + nnueComplexity) / 256;
v = (nnue * scale + optimism * (scale - 748)) / 1024;
}

// Damp down the evaluation linearly when shuffling
v = v * (197 - pos.rule50_count()) / 214;
v = v * (200 - pos.rule50_count()) / 214;

// Guarantee evaluation does not hit the tablebase range
v = std::clamp(v, VALUE_TB_LOSS_IN_MAX_PLY + 1, VALUE_TB_WIN_IN_MAX_PLY - 1);
Expand Down
60 changes: 30 additions & 30 deletions src/search.cpp
View file
Expand Up @@ -63,15 +63,15 @@ namespace {

// Futility margin
Value futility_margin(Depth d, bool improving) {
return Value(165 * (d - improving));
return Value(158 * (d - improving));
}

// Reductions lookup table, initialized at startup
int Reductions[MAX_MOVES]; // [depth or moveNumber]

Depth reduction(bool i, Depth d, int mn, Value delta, Value rootDelta) {
int r = Reductions[d] * Reductions[mn];
return (r + 1642 - int(delta) * 1024 / int(rootDelta)) / 1024 + (!i && r > 916);
return (r + 1460 - int(delta) * 1024 / int(rootDelta)) / 1024 + (!i && r > 937);
}

constexpr int futility_move_count(bool improving, Depth depth) {
Expand All @@ -81,7 +81,7 @@ namespace {

// History and stats update bonus, based on depth
int stat_bonus(Depth d) {
return std::min((12 * d + 282) * d - 349 , 1480);
return std::min((11 * d + 284) * d - 363 , 1650);
}

// Add a small random component to draw evaluations to avoid 3-fold blindness
Expand Down Expand Up @@ -307,7 +307,7 @@ void Thread::search() {

multiPV = std::min(multiPV, rootMoves.size());

complexityAverage.set(155, 1);
complexityAverage.set(153, 1);

optimism[us] = optimism[~us] = VALUE_ZERO;

Expand Down Expand Up @@ -351,12 +351,12 @@ void Thread::search() {
if (rootDepth >= 4)
{
Value prev = rootMoves[pvIdx].averageScore;
delta = Value(10) + int(prev) * prev / 15620;
delta = Value(10) + int(prev) * prev / 15400;
alpha = std::max(prev - delta,-VALUE_INFINITE);
beta = std::min(prev + delta, VALUE_INFINITE);

// Adjust optimism based on root move's previousScore
int opt = 118 * prev / (std::abs(prev) + 169);
int opt = 116 * prev / (std::abs(prev) + 170);
optimism[ us] = Value(opt);
optimism[~us] = -optimism[us];
}
Expand Down Expand Up @@ -753,7 +753,7 @@ namespace {
// Use static evaluation difference to improve quiet move ordering (~4 Elo)
if (is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture)
{
int bonus = std::clamp(-19 * int((ss-1)->staticEval + ss->staticEval), -1914, 1914);
int bonus = std::clamp(-19 * int((ss-1)->staticEval + ss->staticEval), -1940, 1940);
thisThread->mainHistory[~us][from_to((ss-1)->currentMove)] << bonus;
}

Expand All @@ -763,13 +763,13 @@ namespace {
// margin and the improving flag are used in various pruning heuristics.
improvement = (ss-2)->staticEval != VALUE_NONE ? ss->staticEval - (ss-2)->staticEval
: (ss-4)->staticEval != VALUE_NONE ? ss->staticEval - (ss-4)->staticEval
: 168;
: 172;
improving = improvement > 0;

// Step 7. Razoring (~1 Elo).
// If eval is really low check with qsearch if it can exceed alpha, if it can't,
// return a fail low.
if (eval < alpha - 369 - 254 * depth * depth)
if (eval < alpha - 394 - 255 * depth * depth)
{
value = qsearch<NonPV>(pos, ss, alpha - 1, alpha);
if (value < alpha)
Expand All @@ -780,26 +780,26 @@ namespace {
// The depth condition is important for mate finding.
if ( !ss->ttPv
&& depth < 8
&& eval - futility_margin(depth, improving) - (ss-1)->statScore / 303 >= beta
&& eval - futility_margin(depth, improving) - (ss-1)->statScore / 304 >= beta
&& eval >= beta
&& eval < 28031) // larger than VALUE_KNOWN_WIN, but smaller than TB wins
&& eval < 28580) // larger than VALUE_KNOWN_WIN, but smaller than TB wins
return eval;

// Step 9. Null move search with verification search (~35 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
&& (ss-1)->statScore < 17139
&& (ss-1)->statScore < 18200
&& eval >= beta
&& eval >= ss->staticEval
&& ss->staticEval >= beta - 20 * depth - improvement / 13 + 233 + complexity / 25
&& ss->staticEval >= beta - 20 * depth - improvement / 14 + 235 + complexity / 24
&& !excludedMove
&& pos.non_pawn_material(us)
&& (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
{
assert(eval - beta >= 0);

// Null move dynamic reduction based on depth, eval and complexity of position
Depth R = std::min(int(eval - beta) / 168, 7) + depth / 3 + 4 - (complexity > 861);
Depth R = std::min(int(eval - beta) / 165, 6) + depth / 3 + 4 - (complexity > 800);

ss->currentMove = MOVE_NULL;
ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0];
Expand Down Expand Up @@ -835,7 +835,7 @@ namespace {
}
}

probCutBeta = beta + 191 - 54 * improving;
probCutBeta = beta + 180 - 54 * improving;

// Step 10. ProbCut (~10 Elo)
// If we have a good enough capture and a reduced search returns a value
Expand Down Expand Up @@ -904,7 +904,7 @@ namespace {
moves_loop: // When in check, search starts here

// Step 12. A small Probcut idea, when we are in check (~4 Elo)
probCutBeta = beta + 417;
probCutBeta = beta + 402;
if ( ss->inCheck
&& !PvNode
&& depth >= 2
Expand Down Expand Up @@ -999,12 +999,12 @@ namespace {
&& !PvNode
&& lmrDepth < 7
&& !ss->inCheck
&& ss->staticEval + 180 + 201 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))]
&& ss->staticEval + 185 + 203 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))]
+ captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] / 6 < alpha)
continue;

// SEE based pruning (~11 Elo)
if (!pos.see_ge(move, Value(-222) * depth))
if (!pos.see_ge(move, Value(-220) * depth))
continue;
}
else
Expand All @@ -1015,19 +1015,19 @@ namespace {

// Continuation history based pruning (~2 Elo)
if ( lmrDepth < 5
&& history < -3875 * (depth - 1))
&& history < -4180 * (depth - 1))
continue;

history += 2 * thisThread->mainHistory[us][from_to(move)];

// Futility pruning: parent node (~13 Elo)
if ( !ss->inCheck
&& lmrDepth < 13
&& ss->staticEval + 106 + 145 * lmrDepth + history / 52 <= alpha)
&& ss->staticEval + 103 + 136 * lmrDepth + history / 53 <= alpha)
continue;

// Prune moves with negative SEE (~4 Elo)
if (!pos.see_ge(move, Value(-24 * lmrDepth * lmrDepth - 15 * lmrDepth)))
if (!pos.see_ge(move, Value(-25 * lmrDepth * lmrDepth - 16 * lmrDepth)))
continue;
}
}
Expand Down Expand Up @@ -1092,14 +1092,14 @@ namespace {
// Check extensions (~1 Elo)
else if ( givesCheck
&& depth > 9
&& abs(ss->staticEval) > 82)
&& abs(ss->staticEval) > 78)
extension = 1;

// Quiet ttMove extensions (~1 Elo)
else if ( PvNode
&& move == ttMove
&& move == ss->killers[0]
&& (*contHist[0])[movedPiece][to_sq(move)] >= 5177)
&& (*contHist[0])[movedPiece][to_sq(move)] >= 5600)
extension = 1;
}

Expand Down Expand Up @@ -1161,10 +1161,10 @@ namespace {
+ (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)]
- 4433;
- 4467;

// Decrease/increase reduction for moves with a good/bad history (~30 Elo)
r -= ss->statScore / (13000 + 4152 * (depth > 7 && depth < 19));
r -= ss->statScore / (12800 + 4410 * (depth > 7 && depth < 19));

// Step 17. Late moves reduction / extension (LMR, ~117 Elo)
// We use various heuristics for the sons of a node after the first son has
Expand All @@ -1188,7 +1188,7 @@ namespace {
{
// Adjust full depth search based on LMR results - if result
// was good enough search deeper, if it was bad enough search shallower
const bool doDeeperSearch = value > (alpha + 64 + 11 * (newDepth - d));
const bool doDeeperSearch = value > (alpha + 66 + 11 * (newDepth - d));
const bool doEvenDeeperSearch = value > alpha + 582 && ss->doubleExtensions <= 5;
const bool doShallowerSearch = value < bestValue + newDepth;

Expand Down Expand Up @@ -1353,15 +1353,15 @@ namespace {
quietsSearched, quietCount, capturesSearched, captureCount, depth);

// Bonus for prior countermove that caused the fail low
else if ( (depth >= 5 || PvNode || bestValue < alpha - 62 * depth)
else if ( (depth >= 5 || PvNode || bestValue < alpha - 65 * depth)
&& !priorCapture)
{
//Assign extra bonus if current node is PvNode or cutNode
//or fail low was really bad
bool extraBonus = PvNode
|| cutNode;

bool doubleExtraBonus = extraBonus && bestValue < alpha - 85 * depth;
bool doubleExtraBonus = extraBonus && bestValue < alpha - 88 * depth;

update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * (1 + extraBonus + doubleExtraBonus));
}
Expand Down Expand Up @@ -1488,7 +1488,7 @@ namespace {
if (PvNode && bestValue > alpha)
alpha = bestValue;

futilityBase = bestValue + 153;
futilityBase = bestValue + 158;
}

const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
Expand Down Expand Up @@ -1690,7 +1690,7 @@ namespace {

if (!pos.capture(bestMove))
{
int bonus2 = bestValue > beta + 137 ? bonus1 // larger bonus
int bonus2 = bestValue > beta + 146 ? bonus1 // larger bonus
: stat_bonus(depth); // smaller bonus

// Increase stats for the best move in case it was a quiet move
Expand Down

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