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Remove pvExact

The variable pvExact now overlaps with the pvHit concept. So you simplify
the logic with small code tweaks to have pvHit trigger where pvExact
previously triggered.

passed STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 20558 W: 4497 L: 4373 D: 11688
http://tests.stockfishchess.org/tests/view/5c36e9fd0ebc596a450c7885

passed LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 23482 W: 3888 L: 3772 D: 15822
http://tests.stockfishchess.org/tests/view/5c37072d0ebc596a450c7a52

Bench: 3739723
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vondele authored and snicolet committed Jan 10, 2019
1 parent d07e782 commit 5446e6f408f2ed7fa281dbe0097c46674d193260
Showing with 3 additions and 8 deletions.
  1. +3 −8 src/search.cpp
@@ -578,7 +578,7 @@ namespace {
Depth extension, newDepth;
Value bestValue, value, ttValue, eval, maxValue, pureStaticEval;
bool ttHit, pvHit, inCheck, givesCheck, improving;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture, pvExact;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture;
Piece movedPiece;
int moveCount, captureCount, quietCount;

@@ -677,7 +677,7 @@ namespace {
return ttValue;
}

if ( depth > 6 * ONE_PLY
if ( depth > 4 * ONE_PLY
&& !excludedMove
&& PvNode)
pvHit = true;
@@ -898,7 +898,6 @@ namespace {

skipQuiets = false;
ttCapture = ttMove && pos.capture_or_promotion(ttMove);
pvExact = PvNode && ttHit && tte->bound() == BOUND_EXACT;

// Step 12. Loop through all pseudo-legal moves until no moves remain
// or a beta cutoff occurs.
@@ -1043,7 +1042,7 @@ namespace {
Depth r = reduction<PvNode>(improving, depth, moveCount);

// Decrease reduction if position is or has been on the PV
if (pvHit && !PvNode)
if (pvHit)
r -= ONE_PLY;

// Decrease reduction if opponent's move count is high (~10 Elo)
@@ -1052,10 +1051,6 @@ namespace {

if (!captureOrPromotion)
{
// Decrease reduction for exact PV nodes (~0 Elo)
if (pvExact)
r -= ONE_PLY;

// Increase reduction if ttMove is a capture (~0 Elo)
if (ttCapture)
r += ONE_PLY;

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