const Value MidgameLimit = Value(15581);
const Value EndgameLimit = Value(3998);
- // Scale factors used when one side has no more pawns
- const int NoPawnsSF[4] = { 6, 12, 32 };
-
// Polynomial material balance parameters
// pair pawn knight bishop rook queen
// Endgame evaluation and scaling functions are accessed directly and not through
// the function maps because they correspond to more than one material hash key.
- Endgame<KmmKm> EvaluateKmmKm[] = { Endgame<KmmKm>(WHITE), Endgame<KmmKm>(BLACK) };
Endgame<KXK> EvaluateKXK[] = { Endgame<KXK>(WHITE), Endgame<KXK>(BLACK) };
Endgame<KBPsK> ScaleKBPsK[] = { Endgame<KBPsK>(WHITE), Endgame<KBPsK>(BLACK) };
value += pc * v;
}
+
+ // Queen vs. 3 minors slightly favours the minors
+ if (pieceCount[Us][QUEEN] == 1 && pieceCount[Them][QUEEN] == 0)
+ {
+ int n = pieceCount[Them][KNIGHT] - pieceCount[Us][KNIGHT];
+ int b = pieceCount[Them][BISHOP] - pieceCount[Us][BISHOP];
+
+ if ((n == 2 && b == 1) || (n == 1 && b == 2))
+ value -= 66 * 16;
+ }
+
return value;
}
return e;
}
- if (!pos.pieces(PAWN) && !pos.pieces(ROOK) && !pos.pieces(QUEEN))
- {
- // Minor piece endgame with at least one minor piece per side and
- // no pawns. Note that the case KmmK is already handled by KXK.
- assert((pos.pieces(WHITE, KNIGHT) | pos.pieces(WHITE, BISHOP)));
- assert((pos.pieces(BLACK, KNIGHT) | pos.pieces(BLACK, BISHOP)));
-
- if ( pos.count<BISHOP>(WHITE) + pos.count<KNIGHT>(WHITE) <= 2
- && pos.count<BISHOP>(BLACK) + pos.count<KNIGHT>(BLACK) <= 2)
- {
- e->evaluationFunction = &EvaluateKmmKm[pos.side_to_move()];
- return e;
- }
- }
-
// OK, we didn't find any special evaluation function for the current
// material configuration. Is there a suitable scaling function?
//
return e;
}
- // Generic scaling functions that refer to more then one material
+ // Generic scaling functions that refer to more than one material
// distribution. They should be probed after the specialized ones.
// Note that these ones don't return after setting the function.
if (is_KBPsKs<WHITE>(pos))
Value npm_w = pos.non_pawn_material(WHITE);
Value npm_b = pos.non_pawn_material(BLACK);
- if (npm_w + npm_b == VALUE_ZERO)
+ if (npm_w + npm_b == VALUE_ZERO && pos.pieces(PAWN))
{
if (!pos.count<PAWN>(BLACK))
{
}
// No pawns makes it difficult to win, even with a material advantage. This
- // catches some trivial draws like KK, KBK and KNK
+ // catches some trivial draws like KK, KBK and KNK and gives a very drawish
+ // scale factor for cases such as KRKBP and KmmKm (except for KBBKN).
if (!pos.count<PAWN>(WHITE) && npm_w - npm_b <= BishopValueMg)
- {
- e->factor[WHITE] = (uint8_t)
- (npm_w == npm_b || npm_w < RookValueMg ? 0 : NoPawnsSF[std::min(pos.count<BISHOP>(WHITE), 2)]);
- }
+ e->factor[WHITE] = uint8_t(npm_w < RookValueMg ? SCALE_FACTOR_DRAW : npm_b <= BishopValueMg ? 4 : 12);
if (!pos.count<PAWN>(BLACK) && npm_b - npm_w <= BishopValueMg)
- {
- e->factor[BLACK] = (uint8_t)
- (npm_w == npm_b || npm_b < RookValueMg ? 0 : NoPawnsSF[std::min(pos.count<BISHOP>(BLACK), 2)]);
- }
+ e->factor[BLACK] = uint8_t(npm_b < RookValueMg ? SCALE_FACTOR_DRAW : npm_w <= BishopValueMg ? 4 : 12);
if (pos.count<PAWN>(WHITE) == 1 && npm_w - npm_b <= BishopValueMg)
- {
e->factor[WHITE] = (uint8_t) SCALE_FACTOR_ONEPAWN;
- }
if (pos.count<PAWN>(BLACK) == 1 && npm_b - npm_w <= BishopValueMg)
- {
e->factor[BLACK] = (uint8_t) SCALE_FACTOR_ONEPAWN;
- }
// Compute the space weight
if (npm_w + npm_b >= 2 * QueenValueMg + 4 * RookValueMg + 2 * KnightValueMg)