// scores, indexed by a calculated integer number.
Score KingDanger[128];
+ const int ScalePawnSpan[2] = { 38, 56 };
// apply_weight() weighs score 'v' by weight 'w' trying to prevent overflow
Score apply_weight(Score v, const Weight& w) {
}
// Scale winning side if position is more drawish than it appears
- ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
- : ei.mi->scale_factor(pos, BLACK);
+ Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
+ ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
- // If we don't already have an unusual scale factor, check for opposite
- // colored bishop endgames, and use a lower scale for those.
+ // If we don't already have an unusual scale factor, check for certain
+ // types of endgames, and use a lower scale for those.
if ( ei.mi->game_phase() < PHASE_MIDGAME
- && pos.opposite_bishops()
&& (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
{
- // Ignoring any pawns, do both sides only have a single bishop and no
- // other pieces?
- if ( pos.non_pawn_material(WHITE) == BishopValueMg
- && pos.non_pawn_material(BLACK) == BishopValueMg)
- {
- // Check for KBP vs KB with only a single pawn that is almost
- // certainly a draw or at least two pawns.
- bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
- sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
+ if (pos.opposite_bishops()) {
+ // Ignoring any pawns, do both sides only have a single bishop and no
+ // other pieces?
+ if ( pos.non_pawn_material(WHITE) == BishopValueMg
+ && pos.non_pawn_material(BLACK) == BishopValueMg)
+ {
+ // Check for KBP vs KB with only a single pawn that is almost
+ // certainly a draw or at least two pawns.
+ bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
+ sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
+ }
+ else
+ // Endgame with opposite-colored bishops, but also other pieces. Still
+ // a bit drawish, but not as drawish as with only the two bishops.
+ sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
+ } else if ( abs(eg_value(score)) <= BishopValueEg &&
+ ei.pi->pawn_span(strongSide) <= 1 &&
+ !pos.pawn_passed(~strongSide, pos.king_square(~strongSide))) {
+ sf = ScaleFactor(ScalePawnSpan[ei.pi->pawn_span(strongSide)]);
}
- else
- // Endgame with opposite-colored bishops, but also other pieces. Still
- // a bit drawish, but not as drawish as with only the two bishops.
- sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
}
// Interpolate between a middlegame and a (scaled by 'sf') endgame score