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Revert "Guard correction history from overflowing staticEval in the future." #5

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Dec 31, 2023
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Revert "Guard correction history from overflowing staticEval in the future." #5

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46 changes: 16 additions & 30 deletions src/search.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -93,11 +93,6 @@ constexpr int futility_move_count(bool improving, Depth depth) {
return improving ? (3 + depth * depth) : (3 + depth * depth) / 2;
}

// Guarantee evaluation does not hit the tablebase range
constexpr Value to_static_eval(const Value v) {
return std::clamp(v, VALUE_TB_LOSS_IN_MAX_PLY + 1, VALUE_TB_WIN_IN_MAX_PLY - 1);
}

// History and stats update bonus, based on depth
int stat_bonus(Depth d) { return std::min(268 * d - 352, 1153); }

Expand Down Expand Up @@ -715,16 +710,16 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
}
}

Value unadjustedStaticEval = VALUE_NONE;

CapturePieceToHistory& captureHistory = thisThread->captureHistory;

Value unadjustedStaticEval = VALUE_NONE;

// Step 6. Static evaluation of the position
if (ss->inCheck)
{
// Skip early pruning when in check
unadjustedStaticEval = ss->staticEval = eval = VALUE_NONE;
improving = false;
ss->staticEval = eval = VALUE_NONE;
improving = false;
goto moves_loop;
}
else if (excludedMove)
Expand All @@ -743,9 +738,7 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
else if (PvNode)
Eval::NNUE::hint_common_parent_position(pos);

ss->staticEval = eval = to_static_eval(
ss->staticEval
+ Value(thisThread->correctionHistory[us][correction_pawn_structure(pos)] / 16));
ss->staticEval = eval = ss->staticEval + Value(thisThread->correctionHistory[us][correction_pawn_structure(pos)] / 32);

// ttValue can be used as a better position evaluation (~7 Elo)
if (ttValue != VALUE_NONE && (tte->bound() & (ttValue > eval ? BOUND_LOWER : BOUND_UPPER)))
Expand All @@ -755,13 +748,9 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
{
unadjustedStaticEval = ss->staticEval = eval = evaluate(pos);

ss->staticEval = eval = to_static_eval(
ss->staticEval
+ Value(thisThread->correctionHistory[us][correction_pawn_structure(pos)] / 16));
// Save static evaluation into the transposition table
ss->staticEval = eval = ss->staticEval + Value(thisThread->correctionHistory[us][correction_pawn_structure(pos)] / 32);
// Static evaluation is saved as it was before adjustment by correction history
tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE,
unadjustedStaticEval);
tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, unadjustedStaticEval);
}

// Use static evaluation difference to improve quiet move ordering (~4 Elo)
Expand Down Expand Up @@ -1390,12 +1379,14 @@ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, boo
depth, bestMove, unadjustedStaticEval);

// Adjust correction history
if (!ss->inCheck && (!bestMove || !pos.capture(bestMove))
if (!ss->inCheck
&& (!bestMove || !pos.capture(bestMove))
&& !(bestValue >= beta && bestValue <= ss->staticEval)
&& !(!bestMove && bestValue >= ss->staticEval))
thisThread->correctionHistory[us][correction_pawn_structure(pos)]
<< std::clamp(int(bestValue - ss->staticEval) * (16 + depth) / 32,
-CORRECTION_HISTORY_LIMIT / 2, CORRECTION_HISTORY_LIMIT / 2);
thisThread->correctionHistory[us][correction_pawn_structure(pos)] <<
std::clamp(int(bestValue - ss->staticEval) * depth / 8,
-CORRECTION_HISTORY_LIMIT / 4,
CORRECTION_HISTORY_LIMIT / 4);

assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);

Expand Down Expand Up @@ -1489,9 +1480,7 @@ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
if ((unadjustedStaticEval = ss->staticEval = bestValue = tte->eval()) == VALUE_NONE)
unadjustedStaticEval = ss->staticEval = bestValue = evaluate(pos);

ss->staticEval = bestValue = to_static_eval(
ss->staticEval
+ Value(thisThread->correctionHistory[us][correction_pawn_structure(pos)] / 16));
ss->staticEval = bestValue = ss->staticEval + Value(thisThread->correctionHistory[us][correction_pawn_structure(pos)] / 32);

// ttValue can be used as a better position evaluation (~13 Elo)
if (ttValue != VALUE_NONE
Expand All @@ -1503,9 +1492,7 @@ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
// In case of null move search, use previous static eval with a different sign
unadjustedStaticEval = ss->staticEval = bestValue =
(ss - 1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss - 1)->staticEval;
ss->staticEval = bestValue = to_static_eval(
ss->staticEval
+ Value(thisThread->correctionHistory[us][correction_pawn_structure(pos)] / 16));
ss->staticEval = bestValue = ss->staticEval + Value(thisThread->correctionHistory[us][correction_pawn_structure(pos)] / 32);
}

// Stand pat. Return immediately if static value is at least beta
Expand Down Expand Up @@ -1659,8 +1646,7 @@ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
// Save gathered info in transposition table
// Static evaluation is saved as it was before adjustment by correction history
tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit,
bestValue >= beta ? BOUND_LOWER : BOUND_UPPER, ttDepth, bestMove,
unadjustedStaticEval);
bestValue >= beta ? BOUND_LOWER : BOUND_UPPER, ttDepth, bestMove, unadjustedStaticEval);

assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);

Expand Down