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Simplify away best move count logic. #3993

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Simplify away best move count logic. #3993

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16 changes: 4 additions & 12 deletions src/search.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -556,15 +556,15 @@ namespace {
bool givesCheck, improving, didLMR, priorCapture;
bool capture, doFullDepthSearch, moveCountPruning, ttCapture;
Piece movedPiece;
int moveCount, captureCount, quietCount, bestMoveCount, improvement, complexity;
int moveCount, captureCount, quietCount, improvement, complexity;

// Step 1. Initialize node
Thread* thisThread = pos.this_thread();
thisThread->depth = depth;
ss->inCheck = pos.checkers();
priorCapture = pos.captured_piece();
Color us = pos.side_to_move();
moveCount = bestMoveCount = captureCount = quietCount = ss->moveCount = 0;
moveCount = captureCount = quietCount = ss->moveCount = 0;
bestValue = -VALUE_INFINITE;
maxValue = VALUE_INFINITE;

Expand Down Expand Up @@ -1145,11 +1145,6 @@ namespace {
{
Depth r = reduction(improving, depth, moveCount, delta, thisThread->rootDelta);

// Decrease reduction at some PvNodes (~2 Elo)
if ( PvNode
&& bestMoveCount <= 3)
r--;

// Decrease reduction if position is or has been on the PV
// and node is not likely to fail low. (~3 Elo)
if ( ss->ttPv
Expand All @@ -1173,9 +1168,9 @@ namespace {
if (PvNode && !ss->inCheck && abs(ss->staticEval - bestValue) > 250)
r--;

// Increase depth based reduction if PvNode
// Decrease reduction for PvNodes based on depth
if (PvNode)
r -= 15 / ( 3 + depth );
r -= 1 + 15 / ( 3 + depth );

ss->statScore = thisThread->mainHistory[us][from_to(move)]
+ (*contHist[0])[movedPiece][to_sq(move)]
Expand Down Expand Up @@ -1297,10 +1292,7 @@ namespace {
update_pv(ss->pv, move, (ss+1)->pv);

if (PvNode && value < beta) // Update alpha! Always alpha < beta
{
alpha = value;
bestMoveCount++;
}
else
{
assert(value >= beta); // Fail high
Expand Down