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Add TT prefetching support

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TT.retrieve() is the most time consuming function
because almost always involves a very slow RAM access.

TT table is so big that is never cached. This patch
prefetches TT data just after a move is done, so that
subsequent TT.retrieve will be very  fast.

Profiling with VTune shows that TT:retrieve() times are
almost cutted in half !

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2009-08-09 13:44:55 +01:00
parent e6863f46de
commit cd4604b05c
3 changed files with 18 additions and 0 deletions
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5
src/search.cpp
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@@ -1126,6 +1126,7 @@ namespace {
// Make and search the move
StateInfo st;
pos.do_move(move, st, dcCandidates);
TT.prefetch(pos.get_key());
if (moveCount == 1) // The first move in list is the PV
value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
@@ -1296,6 +1297,8 @@ namespace {
StateInfo st;
pos.do_null_move(st);
TT.prefetch(pos.get_key());
int R = (depth >= 5 * OnePly ? 4 : 3); // Null move dynamic reduction
Value nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
@@ -1410,6 +1413,7 @@ namespace {
// Make and search the move
StateInfo st;
pos.do_move(move, st, dcCandidates);
TT.prefetch(pos.get_key());
// Try to reduce non-pv search depth by one ply if move seems not problematic,
// if the move fails high will be re-searched at full depth.
@@ -1619,6 +1623,7 @@ namespace {
// Make and search the move.
StateInfo st;
pos.do_move(move, st, dcCandidates);
TT.prefetch(pos.get_key());
Value value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID);
pos.undo_move(move);