/// TranspositionTable::probe() looks up the current position in the transposition
/// table. It returns true and a pointer to the TTEntry if the position is found.
/// Otherwise, it returns false and a pointer to an empty or least valuable TTEntry
-/// to be replaced later. A TTEntry t1 is considered to be more valuable than a
-/// TTEntry t2 if t1 is from the current search and t2 is from a previous search,
-/// or if the depth of t1 is bigger than the depth of t2.
+/// to be replaced later. TTEntry t1 is considered more valuable than TTEntry t2 if
+/// both are from the current search and the depth of t1 is greater than the depth of t2,
+/// or if t1 is from a previous search but its depth is at least 8 ply deeper than t2.
TTEntry* TranspositionTable::probe(const Key key, bool& found) const {
// Find an entry to be replaced according to the replacement strategy
TTEntry* replace = tte;
for (int i = 1; i < ClusterSize; ++i)
- if ( (( tte[i].genBound8 & 0xFC) == generation8 || tte[i].bound() == BOUND_EXACT)
- - ((replace->genBound8 & 0xFC) == generation8)
- - (tte[i].depth8 < replace->depth8) < 0)
+ if ( (( tte[i].genBound8 & 0xFC) == generation8) * 8 * ONE_PLY + tte[i].depth8
+ < ((replace->genBound8 & 0xFC) == generation8) * 8 * ONE_PLY + replace->depth8)
replace = &tte[i];
return found = false, replace;