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Update Elo estimates for terms in search
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This updates estimates from 2yr ago official-stockfish#2401, and adds missing terms.
All tests run at 10+0.1 (STC), 20000 games, error bars +- 1.8 Elo, book 8moves_v3.png.

A table of Elo values with the links to the corresponding tests can be found at the PR

closes official-stockfish#3868

Non-functional Change
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@BM123499 @vondele
BM123499 authored and vondele committed Dec 21, 2021
1 parent 22e92d2 commit 88f17a8
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Showing 2 changed files with 29 additions and 29 deletions.
2 changes: 1 addition & 1 deletion src/evaluate.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1083,7 +1083,7 @@ Value Eval::evaluate(const Position& pos) {

Value v;

// Deciding between classical and NNUE eval: for high PSQ imbalance we use classical,
// Deciding between classical and NNUE eval (~10 Elo): for high PSQ imbalance we use classical,
// but we switch to NNUE during long shuffling or with high material on the board.

if ( !useNNUE
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56 changes: 28 additions & 28 deletions src/search.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -671,20 +671,20 @@ namespace {
&& (ttValue >= beta ? (tte->bound() & BOUND_LOWER)
: (tte->bound() & BOUND_UPPER)))
{
// If ttMove is quiet, update move sorting heuristics on TT hit
// If ttMove is quiet, update move sorting heuristics on TT hit (~1 Elo)
if (ttMove)
{
if (ttValue >= beta)
{
// Bonus for a quiet ttMove that fails high
// Bonus for a quiet ttMove that fails high (~3 Elo)
if (!ttCapture)
update_quiet_stats(pos, ss, ttMove, stat_bonus(depth));

// Extra penalty for early quiet moves of the previous ply
// Extra penalty for early quiet moves of the previous ply (~0 Elo)
if ((ss-1)->moveCount <= 2 && !priorCapture)
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + 1));
}
// Penalty for a quiet ttMove that fails low
// Penalty for a quiet ttMove that fails low (~1 Elo)
else if (!ttCapture)
{
int penalty = -stat_bonus(depth);
Expand Down Expand Up @@ -773,7 +773,7 @@ namespace {
if (eval == VALUE_DRAW)
eval = value_draw(thisThread);

// Can ttValue be used as a better position evaluation?
// ttValue can be used as a better position evaluation (~4 Elo)
if ( ttValue != VALUE_NONE
&& (tte->bound() & (ttValue > eval ? BOUND_LOWER : BOUND_UPPER)))
eval = ttValue;
Expand All @@ -787,7 +787,7 @@ namespace {
tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
}

// Use static evaluation difference to improve quiet move ordering
// Use static evaluation difference to improve quiet move ordering (~3 Elo)
if (is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture)
{
int bonus = std::clamp(-16 * int((ss-1)->staticEval + ss->staticEval), -2000, 2000);
Expand All @@ -804,15 +804,15 @@ namespace {

improving = improvement > 0;

// Step 7. Futility pruning: child node (~50 Elo).
// Step 7. Futility pruning: child node (~25 Elo).
// The depth condition is important for mate finding.
if ( !ss->ttPv
&& depth < 9
&& eval - futility_margin(depth, improving) >= beta
&& eval < 15000) // 50% larger than VALUE_KNOWN_WIN, but smaller than TB wins.
return eval;

// Step 8. Null move search with verification search (~40 Elo)
// Step 8. Null move search with verification search (~22 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
&& (ss-1)->statScore < 23767
Expand Down Expand Up @@ -925,7 +925,7 @@ namespace {
ss->ttPv = ttPv;
}

// Step 10. If the position is not in TT, decrease depth by 2 or 1 depending on node type
// Step 10. If the position is not in TT, decrease depth by 2 or 1 depending on node type (~3 Elo)
if ( PvNode
&& depth >= 6
&& !ttMove)
Expand All @@ -940,7 +940,7 @@ namespace {

int rangeReduction = 0;

// Step 11. A small Probcut idea, when we are in check
// Step 11. A small Probcut idea, when we are in check (~0 Elo)
probCutBeta = beta + 409;
if ( ss->inCheck
&& !PvNode
Expand Down Expand Up @@ -1017,12 +1017,12 @@ namespace {

Value delta = beta - alpha;

// Step 13. Pruning at shallow depth (~200 Elo). Depth conditions are important for mate finding.
// Step 13. Pruning at shallow depth (~98 Elo). Depth conditions are important for mate finding.
if ( !rootNode
&& pos.non_pawn_material(us)
&& bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
{
// Skip quiet moves if movecount exceeds our FutilityMoveCount threshold
// Skip quiet moves if movecount exceeds our FutilityMoveCount threshold (~7 Elo)
moveCountPruning = moveCount >= futility_move_count(improving, depth);

// Reduced depth of the next LMR search
Expand All @@ -1031,18 +1031,18 @@ namespace {
if ( captureOrPromotion
|| givesCheck)
{
// Futility pruning for captures
// Futility pruning for captures (~0 Elo)
if ( !pos.empty(to_sq(move))
&& !givesCheck
&& !PvNode
&& lmrDepth < 6
&& !ss->inCheck
&& ss->staticEval + 342 + 238 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))]
&& ss->staticEval + 342 + 238 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))]
+ captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] / 8 < alpha)
continue;

// SEE based pruning
if (!pos.see_ge(move, Value(-218) * depth)) // (~25 Elo)
// SEE based pruning (~9 Elo)
if (!pos.see_ge(move, Value(-218) * depth))
continue;
}
else
Expand All @@ -1051,28 +1051,28 @@ namespace {
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)];

// Continuation history based pruning (~20 Elo)
// Continuation history based pruning (~2 Elo)
if ( lmrDepth < 5
&& history < -3000 * depth + 3000)
continue;

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

// Futility pruning: parent node (~5 Elo)
// Futility pruning: parent node (~9 Elo)
if ( !ss->inCheck
&& lmrDepth < 8
&& ss->staticEval + 142 + 139 * lmrDepth + history / 64 <= alpha)
continue;

// Prune moves with negative SEE (~20 Elo)
// Prune moves with negative SEE (~3 Elo)
if (!pos.see_ge(move, Value(-21 * lmrDepth * lmrDepth - 21 * lmrDepth)))
continue;
}
}

// Step 14. Extensions (~75 Elo)
// Step 14. Extensions (~66 Elo)

// Singular extension search (~70 Elo). If all moves but one fail low on a
// Singular extension search (~58 Elo). If all moves but one fail low on a
// search of (alpha-s, beta-s), and just one fails high on (alpha, beta),
// then that move is singular and should be extended. To verify this we do
// a reduced search on all the other moves but the ttMove and if the
Expand Down Expand Up @@ -1117,13 +1117,13 @@ namespace {
extension = -2;
}

// Check extensions
// Check extensions (~1 Elo)
else if ( givesCheck
&& depth > 6
&& abs(ss->staticEval) > 100)
extension = 1;

// Quiet ttMove extensions
// Quiet ttMove extensions (~0 Elo)
else if ( PvNode
&& move == ttMove
&& move == ss->killers[0]
Expand All @@ -1149,7 +1149,7 @@ namespace {

bool doDeeperSearch = false;

// Step 16. Late moves reduction / extension (LMR, ~200 Elo)
// Step 16. Late moves reduction / extension (LMR, ~98 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".
Expand Down Expand Up @@ -1467,7 +1467,7 @@ namespace {
if ((ss->staticEval = bestValue = tte->eval()) == VALUE_NONE)
ss->staticEval = bestValue = evaluate(pos);

// Can ttValue be used as a better position evaluation?
// ttValue can be used as a better position evaluation (~7 Elo)
if ( ttValue != VALUE_NONE
&& (tte->bound() & (ttValue > bestValue ? BOUND_LOWER : BOUND_UPPER)))
bestValue = ttValue;
Expand Down Expand Up @@ -1522,7 +1522,7 @@ namespace {

moveCount++;

// Futility pruning and moveCount pruning
// Futility pruning and moveCount pruning (~5 Elo)
if ( bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& !givesCheck
&& futilityBase > -VALUE_KNOWN_WIN
Expand All @@ -1547,7 +1547,7 @@ namespace {
}
}

// Do not search moves with negative SEE values
// Do not search moves with negative SEE values (~5 Elo)
if ( bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& !pos.see_ge(move))
continue;
Expand All @@ -1561,7 +1561,7 @@ namespace {
[pos.moved_piece(move)]
[to_sq(move)];

// Continuation history based pruning
// Continuation history based pruning (~2 Elo)
if ( !captureOrPromotion
&& bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& (*contHist[0])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold
Expand Down

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