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Don't update bestValue in check_is_dangerous()

Browse source 
It is a prerequisite for next patch and simplifies
the function. testing at ultra fast TC shows no
regression.

After 24302 games at 2"+0.05
Mod vs Orig 5122 - 5038 - 13872 ELO +1 (+- 2.9)

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2012-02-20 14:07:43 +01:00
parent ea5616785e
commit 43f84efa15
1 changed files with 5 additions and 16 deletions
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21
src/search.cpp
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@ -130,7 +130,7 @@ namespace {
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
void id_loop(Position& pos);
bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta);
bool connected_moves(const Position& pos, Move m1, Move m2);
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
@ -1279,7 +1279,7 @@ split_point_start: // At split points actual search starts from here
&& move != ttMove
&& !pos.is_capture_or_promotion(move)
&& ss->eval + PawnValueMidgame / 4 < beta
&& !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
&& !check_is_dangerous(pos, move, futilityBase, beta))
continue;
// Check for legality only before to do the move
@ -1330,13 +1330,12 @@ split_point_start: // At split points actual search starts from here
// bestValue is updated only when returning false because in that case move
// will be pruned.
bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta)
{
Bitboard b, occ, oldAtt, newAtt, kingAtt;
Square from, to, ksq, victimSq;
Square from, to, ksq;
Piece pc;
Color them;
Value futilityValue, bv = *bestValue;
from = from_sq(move);
to = to_sq(move);
@ -1361,23 +1360,13 @@ split_point_start: // At split points actual search starts from here
// Rule 3. Creating new double threats with checks
b = pos.pieces(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
while (b)
{
victimSq = pop_1st_bit(&b);
futilityValue = futilityBase + PieceValueEndgame[pos.piece_on(victimSq)];
// Note that here we generate illegal "double move"!
if ( futilityValue >= beta
&& pos.see_sign(make_move(from, victimSq)) >= 0)
if (futilityBase + PieceValueEndgame[pos.piece_on(pop_1st_bit(&b))] >= beta)
return true;
if (futilityValue > bv)
bv = futilityValue;
}
// Update bestValue only if check is not dangerous (because we will prune the move)
*bestValue = bv;
return false;
}