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Null driven IID: remove IIDMargin from see() condition

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This seems to cut searched nodes also more.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2008-12-10 21:43:09 +01:00
parent ab29d8df67
commit f09884d72f
1 changed files with 5 additions and 4 deletions
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9
src/search.cpp
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@ -1160,7 +1160,7 @@ namespace {
&& ttMove == MOVE_NONE
&& ss[ply + 1].currentMove != MOVE_NONE
&& pos.move_is_capture(ss[ply + 1].currentMove)
&& pos.see(ss[ply + 1].currentMove) * PawnValueMidgame + nullValue > beta - IIDMargin)
&& pos.see(ss[ply + 1].currentMove) + nullValue >= beta)
nullDrivenIID = true;
pos.undo_null_move(u);
@ -1176,9 +1176,9 @@ namespace {
return beta;
} else {
// The null move failed low, which means that we may be faced with
// some kind of threat. If the previous move was reduced, check if
// some kind of threat. If the previous move was reduced, check if
// the move that refuted the null move was somehow connected to the
// move which was reduced. If a connection is found, return a fail
// move which was reduced. If a connection is found, return a fail
// low score (which will cause the reduced move to fail high in the
// parent node, which will trigger a re-search with full depth).
if (nullValue == value_mated_in(ply + 2))
@ -1217,8 +1217,9 @@ namespace {
Move tm = ss[ply].threatMove;
assert(tm != MOVE_NONE);
assert(ttMove == MOVE_NONE);
search(pos, ss, beta, Min(depth/2, depth-3*OnePly), ply, false, threadID);
search(pos, ss, beta, depth/2, ply, false, threadID);
ttMove = ss[ply].pv[ply];
ss[ply].threatMove = tm;
}