along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-
-////
-//// Includes
-////
-
#include <cassert>
-#include <cstring>
+#include "bitboard.h"
#include "bitcount.h"
#include "pawns.h"
#include "position.h"
-
-////
-//// Local definitions
-////
-
namespace {
- /// Constants and variables
-
#define S(mg, eg) make_score(mg, eg)
// Doubled pawn penalty by opposed flag and file
}
-////
-//// Functions
-////
-
-
/// PawnInfoTable::get_pawn_info() takes a position object as input, computes
/// a PawnInfo object, and returns a pointer to it. The result is also stored
-/// in a hash table, so we don't have to recompute everything when the same
+/// in an hash table, so we don't have to recompute everything when the same
/// pawn structure occurs again.
PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) const {
if (pi->key == key)
return pi;
- // Clear the PawnInfo object, and set the key
- memset(pi, 0, sizeof(PawnInfo));
- pi->halfOpenFiles[WHITE] = pi->halfOpenFiles[BLACK] = 0xFF;
- pi->kingSquares[WHITE] = pi->kingSquares[BLACK] = SQ_NONE;
+ // Initialize PawnInfo entry
pi->key = key;
+ pi->passedPawns[WHITE] = pi->passedPawns[BLACK] = 0;
+ pi->kingSquares[WHITE] = pi->kingSquares[BLACK] = SQ_NONE;
+ pi->halfOpenFiles[WHITE] = pi->halfOpenFiles[BLACK] = 0xFF;
// Calculate pawn attacks
Bitboard wPawns = pos.pieces(PAWN, WHITE);
template<Color Us>
Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
Bitboard theirPawns, PawnInfo* pi) const {
+
+ const BitCountType Max15 = CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
+
Bitboard b;
Square s;
File f;
Rank r;
bool passed, isolated, doubled, opposed, chain, backward, candidate;
Score value = SCORE_ZERO;
- const BitCountType Max15 = CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
const Square* ptr = pos.piece_list_begin(Us, PAWN);
// Loop through all pawns of the current color and score each pawn
// This file cannot be half open
pi->halfOpenFiles[Us] &= ~(1 << f);
- // Our rank plus previous one. Used for chain detection.
+ // Our rank plus previous one. Used for chain detection
b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1));
- // Passed, isolated, doubled or member of a pawn
- // chain (but not the backward one) ?
+ // Flag the pawn as passed, isolated, doubled or member of a pawn
+ // chain (but not the backward one).
passed = !(theirPawns & passed_pawn_mask(Us, s));
doubled = ourPawns & squares_in_front_of(Us, s);
opposed = theirPawns & squares_in_front_of(Us, s);
chain = ourPawns & neighboring_files_bb(f) & b;
// Test for backward pawn
- //
backward = false;
- // If the pawn is passed, isolated, or member of a pawn chain
- // it cannot be backward. If can capture an enemy pawn or if
- // there are friendly pawns behind on neighboring files it cannot
- // be backward either.
+ // If the pawn is passed, isolated, or member of a pawn chain it cannot
+ // be backward. If there are friendly pawns behind on neighboring files
+ // or if can capture an enemy pawn it cannot be backward either.
if ( !(passed | isolated | chain)
- && !(ourPawns & attack_span_mask(opposite_color(Us), s))
+ && !(ourPawns & attack_span_mask(Them, s))
&& !(pos.attacks_from<PAWN>(s, Us) & theirPawns))
{
// We now know that there are no friendly pawns beside or behind this
while (!(b & (ourPawns | theirPawns)))
Us == WHITE ? b <<= 8 : b >>= 8;
- // The friendly pawn needs to be at least two ranks closer than the enemy
- // pawn in order to help the potentially backward pawn advance.
+ // The friendly pawn needs to be at least two ranks closer than the
+ // enemy pawn in order to help the potentially backward pawn advance.
backward = (b | (Us == WHITE ? b << 8 : b >> 8)) & theirPawns;
}
- assert(passed | opposed | (attack_span_mask(Us, s) & theirPawns));
+ assert(opposed | passed | (attack_span_mask(Us, s) & theirPawns));
- // Test for candidate passed pawn
- candidate = !(opposed | passed)
- && (b = attack_span_mask(opposite_color(Us), s + pawn_push(Us)) & ourPawns) != EmptyBoardBB
+ // 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 neighboring files is higher or equal than the number of
+ // enemy pawns in the forward direction on the neighboring files.
+ candidate = !(opposed | passed | backward | isolated)
+ && (b = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != EmptyBoardBB
&& count_1s<Max15>(b) >= count_1s<Max15>(attack_span_mask(Us, s) & theirPawns);
- // Mark the pawn as passed. Pawn 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.
+ // 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.
if (passed && !doubled)
set_bit(&(pi->passedPawns[Us]), s);
}
return value;
}
+
+
+/// PawnInfo::updateShelter() calculates and caches king shelter. It is called
+/// only when king square changes, about 20% of total king_shelter() calls.
+template<Color Us>
+Score PawnInfo::updateShelter(const Position& pos, Square ksq) {
+
+ const int Shift = (Us == WHITE ? 8 : -8);
+
+ Bitboard pawns;
+ int r, shelter = 0;
+
+ if (relative_rank(Us, ksq) <= RANK_4)
+ {
+ pawns = pos.pieces(PAWN, Us) & this_and_neighboring_files_bb(ksq);
+ r = ksq & (7 << 3);
+ for (int i = 0; i < 3; i++)
+ {
+ r += Shift;
+ shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (64 >> i);
+ }
+ }
+ kingSquares[Us] = ksq;
+ kingShelters[Us] = make_score(shelter, 0);
+ return kingShelters[Us];
+}
+
+// Explicit template instantiation
+template Score PawnInfo::updateShelter<WHITE>(const Position& pos, Square ksq);
+template Score PawnInfo::updateShelter<BLACK>(const Position& pos, Square ksq);
#if !defined(PAWNS_H_INCLUDED)
#define PAWNS_H_INCLUDED
-#include "bitboard.h"
#include "position.h"
#include "tt.h"
#include "types.h"
/// method is get_pawn_info, which returns a pointer to a PawnInfo object.
class PawnInfoTable : public SimpleHash<PawnInfo, PawnTableSize> {
-
- enum SideType { KingSide, QueenSide };
-
public:
PawnInfo* get_pawn_info(const Position& pos) const;
- void prefetch(Key key) const;
private:
template<Color Us>
Score evaluate_pawns(const Position& pos, Bitboard ourPawns, Bitboard theirPawns, PawnInfo* pi) const;
};
-inline Square pawn_push(Color c) {
- return c == WHITE ? DELTA_N : DELTA_S;
-}
-
-inline void PawnInfoTable::prefetch(Key key) const {
-
- unsigned index = unsigned(key & (PawnTableSize - 1));
- PawnInfo* pi = entries + index;
- ::prefetch((char*) pi);
-}
inline Score PawnInfo::pawns_value() const {
return value;
}
inline int PawnInfo::file_is_half_open(Color c, File f) const {
- return (halfOpenFiles[c] & (1 << int(f)));
+ return halfOpenFiles[c] & (1 << int(f));
}
inline int PawnInfo::has_open_file_to_left(Color c, File f) const {
return halfOpenFiles[c] & ~((1 << int(f+1)) - 1);
}
-/// PawnInfo::updateShelter() calculates and caches king shelter. It is called
-/// only when king square changes, about 20% of total king_shelter() calls.
-template<Color Us>
-Score PawnInfo::updateShelter(const Position& pos, Square ksq) {
-
- const int Shift = (Us == WHITE ? 8 : -8);
-
- Bitboard pawns;
- int r, shelter = 0;
-
- if (relative_rank(Us, ksq) <= RANK_4)
- {
- pawns = pos.pieces(PAWN, Us) & this_and_neighboring_files_bb(ksq);
- r = square_rank(ksq) * 8;
- for (int i = 1; i < 4; i++)
- {
- r += Shift;
- shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (128 >> i);
- }
- }
- kingSquares[Us] = ksq;
- kingShelters[Us] = make_score(shelter, 0);
- return kingShelters[Us];
-}
-
template<Color Us>
inline Score PawnInfo::king_shelter(const Position& pos, Square ksq) {
return kingSquares[Us] == ksq ? kingShelters[Us] : updateShelter<Us>(pos, ksq);
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