{ S(20, 28), S(29, 31), S(33, 31), S(33, 31),
S(33, 31), S(33, 31), S(29, 31), S(20, 28) } };
- // Connected pawn bonus by file and rank (initialized by formula)
- Score Connected[FILE_NB][RANK_NB];
-
- // Candidate passed pawn bonus by rank
- const Score CandidatePassed[RANK_NB] = {
- S( 0, 0), S( 6, 13), S(6,13), S(14,29),
- S(34,68), S(83,166), S(0, 0), S( 0, 0) };
+ // Connected pawn bonus by opposed, phalanx flags and rank
+ Score Connected[2][2][RANK_NB];
// Levers bonus by rank
const Score Lever[RANK_NB] = {
S( 0, 0), S( 0, 0), S(0, 0), S(0, 0),
S(20,20), S(40,40), S(0, 0), S(0, 0) };
- // Bonus for file distance of the two outermost pawns
- const Score PawnsFileSpan = S(0, 15);
-
// Unsupported pawn penalty
const Score UnsupportedPawnPenalty = S(20, 10);
const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
- Bitboard b, p, doubled;
+ Bitboard b, p, doubled, connected;
Square s;
- File f;
- bool passed, isolated, opposed, connected, backward, candidate, unsupported, lever;
+ bool passed, isolated, opposed, phalanx, backward, unsupported, lever;
Score value = SCORE_ZERO;
const Square* pl = pos.list<PAWN>(Us);
const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
- Bitboard ourPawns = pos.pieces(Us, PAWN);
+ Bitboard ourPawns = pos.pieces(Us , PAWN);
Bitboard theirPawns = pos.pieces(Them, PAWN);
- e->passedPawns[Us] = e->candidatePawns[Us] = 0;
+ e->passedPawns[Us] = 0;
e->kingSquares[Us] = SQ_NONE;
e->semiopenFiles[Us] = 0xFF;
e->pawnAttacks[Us] = shift_bb<Right>(ourPawns) | shift_bb<Left>(ourPawns);
{
assert(pos.piece_on(s) == make_piece(Us, PAWN));
- f = file_of(s);
+ File f = file_of(s);
// This file cannot be semi-open
e->semiopenFiles[Us] &= ~(1 << f);
// Previous rank
p = rank_bb(s - pawn_push(Us));
- // Our rank plus previous one
- b = rank_bb(s) | p;
-
// Flag the pawn as passed, isolated, doubled,
// unsupported or connected (but not the backward one).
- connected = ourPawns & adjacent_files_bb(f) & b;
+ connected = ourPawns & adjacent_files_bb(f) & (rank_bb(s) | p);
+ phalanx = connected & rank_bb(s);
unsupported = !(ourPawns & adjacent_files_bb(f) & p);
isolated = !(ourPawns & adjacent_files_bb(f));
doubled = ourPawns & forward_bb(Us, s);
assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns));
- // A not-passed pawn is a candidate to become passed, if it is free to
- // advance and if the number of friendly pawns beside or behind this
- // pawn on adjacent files is higher than or equal to the number of
- // enemy pawns in the forward direction on the adjacent files.
- candidate = !(opposed | passed | backward | isolated)
- && (b = pawn_attack_span(Them, s + pawn_push(Us)) & ourPawns) != 0
- && popcount<Max15>(b) >= popcount<Max15>(pawn_attack_span(Us, s) & theirPawns);
-
// Passed pawns will be properly scored in evaluation because we need
// full attack info to evaluate passed pawns. Only the frontmost passed
// pawn on each file is considered a true passed pawn.
value -= UnsupportedPawnPenalty;
if (doubled)
- value -= Doubled[f] / rank_distance(s, lsb(doubled));
+ value -= Doubled[f] / distance<Rank>(s, frontmost_sq(Us, doubled));
if (backward)
value -= Backward[opposed][f];
if (connected)
- value += Connected[f][relative_rank(Us, s)];
+ value += Connected[opposed][phalanx][relative_rank(Us, s)];
if (lever)
- value += Lever[relative_rank(Us, s)];
-
- if (candidate)
- {
- value += CandidatePassed[relative_rank(Us, s)];
-
- if (!doubled)
- e->candidatePawns[Us] |= s;
- }
+ value += Lever[relative_rank(Us, s)];
}
b = e->semiopenFiles[Us] ^ 0xFF;
e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
- // In endgame it's better to have pawns on both wings. So give a bonus according
- // to file distance between left and right outermost pawns.
- value += PawnsFileSpan * e->pawnSpan[Us];
-
return value;
}
namespace Pawns {
-/// init() initializes some tables by formula instead of hard-coding their values
-
-void init() {
-
- const int bonusByFile[] = { 1, 3, 3, 4, 4, 3, 3, 1 };
-
- for (Rank r = RANK_1; r < RANK_8; ++r)
- for (File f = FILE_A; f <= FILE_H; ++f)
- {
- int bonus = r * (r - 1) * (r - 2) + bonusByFile[f] * (r / 2 + 1);
- Connected[f][r] = make_score(bonus, bonus);
- }
+/// init() initializes some tables used by evaluation. Instead of hard-coded
+/// tables, when makes sense, we prefer to calculate them with a formula to
+/// reduce independent parameters and to allow easier tuning and better insight.
+
+void init()
+{
+ static const int Seed[RANK_NB] = { 0, 6, 15, 10, 57, 75, 135, 258 };
+
+ for (int opposed = 0; opposed <= 1; ++opposed)
+ for (int phalanx = 0; phalanx <= 1; ++phalanx)
+ for (Rank r = RANK_2; r < RANK_8; ++r)
+ {
+ int bonus = Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0);
+ Connected[opposed][phalanx][r] = make_score(bonus / 2, bonus >> opposed);
+ }
}
kingSquares[Us] = ksq;
castlingRights[Us] = pos.can_castle(Us);
- minKPdistance[Us] = 0;
+ minKingPawnDistance[Us] = 0;
Bitboard pawns = pos.pieces(Us, PAWN);
if (pawns)
- while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {}
+ while (!(DistanceRingsBB[ksq][minKingPawnDistance[Us]++] & pawns)) {}
if (relative_rank(Us, ksq) > RANK_4)
- return make_score(0, -16 * minKPdistance[Us]);
+ return make_score(0, -16 * minKingPawnDistance[Us]);
Value bonus = shelter_storm<Us>(pos, ksq);
if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
- return make_score(bonus, -16 * minKPdistance[Us]);
+ return make_score(bonus, -16 * minKingPawnDistance[Us]);
}
// Explicit template instantiation
projects / stockfish / blobdiff