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In qsearch store the cut move in TT

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And upon reentering the same position try it as first.

Normally qsearch moves order is already very good, first move
is the cut off in almost 90% of cases. With this patch, we get
a cut off on TT move of 98%.

Another good side effect is that we don't generate captures
and/or checks when we already have a TT move.

Unfortunatly we found a TT move only in 1% of cases. So real
impact of this patch is relatively low.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2009-04-18 14:03:33 +01:00
parent 4634be8ba6
commit e68ebe618c
3 changed files with 14 additions and 25 deletions
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src/search.cpp
+5 -6
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@@ -1516,6 +1516,7 @@ namespace {
return value_from_tt(tte->value(), ply);
}
}
Move ttMove = (tte ? tte->move() : MOVE_NONE);
// Evaluate the position statically
EvalInfo ei;
@@ -1559,7 +1560,7 @@ namespace {
// Initialize a MovePicker object for the current position, and prepare
// to search the moves. Because the depth is <= 0 here, only captures,
// queen promotions and checks (only if depth == 0) will be generated.
MovePicker mp = MovePicker(pos, pvNode, MOVE_NONE, EmptySearchStack, depth);
MovePicker mp = MovePicker(pos, pvNode, ttMove, EmptySearchStack, depth);
Move move;
int moveCount = 0;
Bitboard dcCandidates = mp.discovered_check_candidates();
@@ -1636,22 +1637,20 @@ namespace {
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
// Update transposition table
Move m = ss[ply].pv[ply];
if (!pvNode)
{
Depth d = (depth == Depth(0) ? Depth(0) : Depth(-1));
if (bestValue < beta)
TT.store(pos, value_to_tt(bestValue, ply), d, MOVE_NONE, VALUE_TYPE_UPPER);
else
TT.store(pos, value_to_tt(bestValue, ply), d, MOVE_NONE, VALUE_TYPE_LOWER);
TT.store(pos, value_to_tt(bestValue, ply), d, m, VALUE_TYPE_LOWER);
}
// Update killers only for good check moves
Move m = ss[ply].currentMove;
if (alpha >= beta && ok_to_history(pos, m)) // Only non capture moves are considered
{
// Wrong to update history when depth is <= 0
update_killers(m, ss[ply]);
}
return bestValue;
}