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Better document entry age calculation used in TT replace.

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No functional change.

Resolves #401
Resolves #400
This commit is contained in:
mstembera
2015-08-20 20:24:37 +01:00
committed by Joona Kiiski
parent c052e03426
commit bf6bc1b37b
1 changed files with 4 additions and 0 deletions
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4
src/tt.cpp
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@@ -87,6 +87,10 @@ TTEntry* TranspositionTable::probe(const Key key, bool& found) const {
// Find an entry to be replaced according to the replacement strategy // Find an entry to be replaced according to the replacement strategy
TTEntry* replace = tte; TTEntry* replace = tte;
for (int i = 1; i < ClusterSize; ++i) for (int i = 1; i < ClusterSize; ++i)
// Due to our packed storage format for generation and its cyclic
// nature we add 259 (256 is the modulus plus 3 to keep the lowest
// two bound bits from affecting the result) to calculate the entry
// age correctly even after generation8 overflows into the next cycle.
if ( replace->depth8 - ((259 + generation8 - replace->genBound8) & 0xFC) * 2 * ONE_PLY if ( replace->depth8 - ((259 + generation8 - replace->genBound8) & 0xFC) * 2 * ONE_PLY
> tte[i].depth8 - ((259 + generation8 - tte[i].genBound8) & 0xFC) * 2 * ONE_PLY) > tte[i].depth8 - ((259 + generation8 - tte[i].genBound8) & 0xFC) * 2 * ONE_PLY)
replace = &tte[i]; replace = &tte[i];