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Try to prefetch as soon as position key is ready

Browse Source 
Move prefetching code inside do_move() so to allow a
very early prefetching and to put as many instructions
as possible between prefetching and following retrieve().

With this patch retrieve() times are cutted of another 25%

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2009-08-09 15:53:51 +01:00
parent cd4604b05c
commit 4251eac860
4 changed files with 74 additions and 45 deletions
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21
src/tt.cpp
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@@ -93,6 +93,16 @@ void TranspositionTable::clear() {
}
/// TranspositionTable::first_entry returns a pointer to the first
/// entry of a cluster given a position. The low 32 bits of the key
/// are used to get the index in the table.
inline TTEntry* TranspositionTable::first_entry(const Key posKey) const {
return entries + ((uint32_t(posKey) & (size - 1)) * ClusterSize);
}
/// TranspositionTable::store writes a new entry containing a position,
/// a value, a value type, a search depth, and a best move to the
/// transposition table. Transposition table is organized in clusters of
@@ -145,7 +155,7 @@ void TranspositionTable::store(const Key posKey, Value v, ValueType t, Depth d,
TTEntry* TranspositionTable::retrieve(const Key posKey) const {
uint32_t posKey32 = posKey >> 32;
TTEntry *tte = first_entry(posKey);
TTEntry* tte = first_entry(posKey);
for (int i = 0; i < ClusterSize; i++, tte++)
if (tte->key() == posKey32)
@@ -154,6 +164,7 @@ TTEntry* TranspositionTable::retrieve(const Key posKey) const {
return NULL;
}
/// TranspositionTable::prefetch looks up the current position in the
/// transposition table and load it in L1/L2 cache. This is a non
/// blocking function and do not stalls the CPU waiting for data
@@ -166,14 +177,6 @@ void TranspositionTable::prefetch(const Key posKey) const {
_mm_prefetch((char*)first_entry(posKey), _MM_HINT_T0);
}
/// TranspositionTable::first_entry returns a pointer to the first
/// entry of a cluster given a position. The low 32 bits of the key
/// are used to get the index in the table.
inline TTEntry* TranspositionTable::first_entry(const Key posKey) const {
return entries + ((uint32_t(posKey) & (size - 1)) * ClusterSize);
}
/// TranspositionTable::new_search() is called at the beginning of every new
/// search. It increments the "generation" variable, which is used to