Reduce writes in TT::probe().

mstembera · mstembera · commit f1452266597c · 2015-09-22T21:38:29.000-07:00
Only refresh TT entry when it's really necessary. This should give a small speed boost for some machines. And it's a risk-free change. No functional change. Resolves official-stockfish#429
diff --git a/src/tt.cpp b/src/tt.cpp
@@ -78,7 +78,7 @@ TTEntry* TranspositionTable::probe(const Key key, bool& found) const {
   for (int i = 0; i < ClusterSize; ++i)
       if (!tte[i].key16 || tte[i].key16 == key16)
       {
-          if (tte[i].key16)
+          if ((tte[i].genBound8 & 0xFC) != generation8 && tte[i].key16)
               tte[i].genBound8 = uint8_t(generation8 | tte[i].bound()); // Refresh
 
           return found = (bool)tte[i].key16, &tte[i];

Original file line number	Diff line number	Diff line change
`@@ -78,7 +78,7 @@ TTEntry* TranspositionTable::probe(const Key key, bool& found) const {`
`78`	`78`	`for (int i = 0; i < ClusterSize; ++i)`
`79`	`79`	`if (!tte[i].key16 \|\| tte[i].key16 == key16)`
`80`	`80`	`{`
`81`		`- if (tte[i].key16)`
	`81`	`+ if ((tte[i].genBound8 & 0xFC) != generation8 && tte[i].key16)`
`82`	`82`	`tte[i].genBound8 = uint8_t(generation8 \| tte[i].bound()); // Refresh`
`83`	`83`
`84`	`84`	`return found = (bool)tte[i].key16, &tte[i];`