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Smart TT save

Don't overwrite more valuable data with less valuable data

STC 2MB
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 21132 W: 4108 L: 3946 D: 13078
http://tests.stockfishchess.org/tests/view/5547d59f0ebc5940ca5d6883

LTC 8MB
LLR: 2.97 (-2.94,2.94) [0.00,6.00]
Total: 13381 W: 2149 L: 1987 D: 9245
http://tests.stockfishchess.org/tests/view/5549b5a80ebc5940ca5d68b9

STC 16MB regression w/ zero effective hash pressure
LLR: 2.96 (-2.94,2.94) [-5.00,0.00]
Total: 18944 W: 3607 L: 3564 D: 11773
http://tests.stockfishchess.org/tests/view/554b0fda0ebc5940ca5d68ea

Bench: 8787152

Resolves official-stockfish#347
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mstembera authored and zamar committed May 9, 2015
1 parent 92dbee7 commit eaeb63f1d03aa71edf719605a31d121bf086a03d
Showing with 28 additions and 8 deletions.
  1. +28 −8 src/tt.h
@@ -43,14 +43,34 @@ struct TTEntry {

void save(Key k, Value v, Bound b, Depth d, Move m, Value ev, uint8_t g) {

if (m || (k >> 48) != key16) // Preserve any existing move for the same position
move16 = (uint16_t)m;

key16 = (uint16_t)(k >> 48);
value16 = (int16_t)v;
eval16 = (int16_t)ev;
genBound8 = (uint8_t)(g | b);
depth8 = (int8_t)d;
if (key16 != (k >> 48))
{
key16 = (uint16_t)(k >> 48);
move16 = (uint16_t)m;
value16 = (int16_t)v;
eval16 = (int16_t)ev;
genBound8 = (uint8_t)(g | b);
depth8 = (int8_t)d;
}
else
{
// Preserve any existing move for the same position
if (m)
move16 = (uint16_t)m;

// Don't overwrite more valuable values
if ( d + 2 > depth8
|| g != (genBound8 & 0xFC)
|| b == BOUND_EXACT)
{
value16 = (int16_t)v;
genBound8 = (uint8_t)(g | b);
depth8 = (int8_t)d;
}

if (ev != VALUE_NONE)
eval16 = (int16_t)ev;
}
}

private:

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