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Additional cleanup in bitbase.cpp
Also better document what code does. No functional change. Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
parent
c1c0984452
commit
635be39acf
2 changed files with 48 additions and 85 deletions
131
src/bitbase.cpp
131
src/bitbase.cpp
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@ -45,9 +45,11 @@ namespace {
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Color sideToMove;
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};
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const int IndexMax = 2 * 24 * 64 * 64;
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// The possible pawns squares are 24, the first 4 files and ranks from 2 to 7
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const int IndexMax = 2 * 24 * 64 * 64; // color * wp_sq * wk_sq * bk_sq
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uint8_t KPKBitbase[IndexMax / 8];
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// Each uint32_t stores results of 32 positions, one per bit
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uint32_t KPKBitbase[IndexMax / 32];
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Result classify_wtm(const KPKPosition& pos, const Result bb[]);
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Result classify_btm(const KPKPosition& pos, const Result bb[]);
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@ -55,23 +57,22 @@ namespace {
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}
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int probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm) {
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uint32_t probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm) {
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int index = compute_index(wksq, bksq, wpsq, stm);
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return KPKBitbase[index / 8] & (1 << (index & 7));
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return KPKBitbase[index / 32] & (1 << (index & 31));
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}
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void init_kpk_bitbase() {
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bool repeat;
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int i, j, b;
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KPKPosition pos;
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Result bb[IndexMax];
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KPKPosition pos;
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bool repeat;
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// Initialize table
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for (i = 0; i < IndexMax; i++)
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for (int i = 0; i < IndexMax; i++)
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{
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pos.from_index(i);
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bb[i] = !pos.is_legal() ? RESULT_INVALID
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@ -83,7 +84,7 @@ void init_kpk_bitbase() {
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do {
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repeat = false;
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for (i = 0; i < IndexMax; i++)
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for (int i = 0; i < IndexMax; i++)
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if (bb[i] == RESULT_UNKNOWN)
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{
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pos.from_index(i);
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@ -96,29 +97,36 @@ void init_kpk_bitbase() {
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} while (repeat);
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// Compress result and map into KPKBitbase[]
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for (i = 0; i < 24576; i++)
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{
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b = 0;
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for (j = 0; j < 8; j++)
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if (bb[8*i+j] == RESULT_WIN || bb[8*i+j] == RESULT_LOSS)
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b |= (1 << j);
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KPKBitbase[i] = (uint8_t)b;
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}
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// Map 32 position results into one KPKBitbase[] entry
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for (int i = 0; i < IndexMax / 32; i++)
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for (int j = 0; j < 32; j++)
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if (bb[32 * i + j] == RESULT_WIN || bb[32 * i + j] == RESULT_LOSS)
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KPKBitbase[i] |= (1 << j);
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}
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namespace {
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// A KPK bitbase index is an integer in [0, IndexMax] range
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//
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// Information is mapped in this way
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//
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// bit 0: side to move (WHITE or BLACK)
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// bit 1- 6: black king square (from SQ_A1 to SQ_H8)
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// bit 7-12: white king square (from SQ_A1 to SQ_H8)
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// bit 13-14: white pawn file (from FILE_A to FILE_D)
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// bit 15-17: white pawn rank - 1 (from RANK_2 - 1 to RANK_7 - 1)
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int compute_index(Square wksq, Square bksq, Square wpsq, Color stm) {
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int p = int(square_file(wpsq)) + (int(square_rank(wpsq)) - 1) * 4;
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int r = int(stm) + 2 * int(bksq) + 128 * int(wksq) + 8192 * p;
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assert(square_file(wpsq) <= FILE_D);
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assert(r >= 0 && r < IndexMax);
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int p = int(square_file(wpsq)) + 4 * int(square_rank(wpsq) - 1);
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int r = int(stm) + 2 * int(bksq) + 128 * int(wksq) + 8192 * p;
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return r;
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assert(r >= 0 && r < IndexMax);
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return r;
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}
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void KPKPosition::from_index(int index) {
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@ -135,7 +143,7 @@ namespace {
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if ( whiteKingSquare == pawnSquare
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|| whiteKingSquare == blackKingSquare
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|| pawnSquare == blackKingSquare)
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|| blackKingSquare == pawnSquare)
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return false;
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if (sideToMove == WHITE)
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@ -167,16 +175,11 @@ namespace {
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}
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else
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{
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// Case 1: Stalemate
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// Case 1: Stalemate (possible pawn files are only from A to D)
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if ( whiteKingSquare == SQ_A8
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&& pawnSquare == SQ_A7
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&& (blackKingSquare == SQ_C7 || blackKingSquare == SQ_C8))
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return true;
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if ( whiteKingSquare == SQ_H8
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&& pawnSquare == SQ_H7
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&& (blackKingSquare == SQ_F7 || blackKingSquare == SQ_F8))
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return true;
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}
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return false;
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}
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@ -202,77 +205,47 @@ namespace {
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bool unknownFound = false;
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Bitboard b;
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Square s;
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int idx;
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Result r;
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// King moves
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b = pos.wk_attacks();
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while (b)
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{
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s = pop_1st_bit(&b);
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idx = compute_index(s, pos.blackKingSquare, pos.pawnSquare, BLACK);
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r = bb[compute_index(s, pos.blackKingSquare, pos.pawnSquare, BLACK)];
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switch (bb[idx]) {
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case RESULT_LOSS:
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if (r == RESULT_LOSS)
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return RESULT_WIN;
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case RESULT_UNKNOWN:
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if (r == RESULT_UNKNOWN)
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unknownFound = true;
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case RESULT_DRAW:
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case RESULT_INVALID:
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break;
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default:
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assert(false);
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}
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}
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// Pawn moves
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if (square_rank(pos.pawnSquare) < RANK_7)
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{
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s = pos.pawnSquare + DELTA_N;
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idx = compute_index(pos.whiteKingSquare, pos.blackKingSquare, s, BLACK);
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r = bb[compute_index(pos.whiteKingSquare, pos.blackKingSquare, s, BLACK)];
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switch (bb[idx]) {
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case RESULT_LOSS:
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if (r == RESULT_LOSS)
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return RESULT_WIN;
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case RESULT_UNKNOWN:
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if (r == RESULT_UNKNOWN)
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unknownFound = true;
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case RESULT_DRAW:
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case RESULT_INVALID:
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break;
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default:
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assert(false);
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}
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// Double pawn push
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if ( square_rank(s) == RANK_3
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&& s != pos.whiteKingSquare
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&& s != pos.blackKingSquare)
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{
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s += DELTA_N;
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idx = compute_index(pos.whiteKingSquare, pos.blackKingSquare, s, BLACK);
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r = bb[compute_index(pos.whiteKingSquare, pos.blackKingSquare, s, BLACK)];
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switch (bb[idx]) {
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case RESULT_LOSS:
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if (r == RESULT_LOSS)
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return RESULT_WIN;
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case RESULT_UNKNOWN:
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if (r == RESULT_UNKNOWN)
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unknownFound = true;
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case RESULT_DRAW:
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case RESULT_INVALID:
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break;
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default:
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assert(false);
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}
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}
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}
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return unknownFound ? RESULT_UNKNOWN : RESULT_DRAW;
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@ -290,30 +263,20 @@ namespace {
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bool unknownFound = false;
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Bitboard b;
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Square s;
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int idx;
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Result r;
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// King moves
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b = pos.bk_attacks();
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while (b)
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{
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s = pop_1st_bit(&b);
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idx = compute_index(pos.whiteKingSquare, s, pos.pawnSquare, WHITE);
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r = bb[compute_index(pos.whiteKingSquare, s, pos.pawnSquare, WHITE)];
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switch (bb[idx]) {
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case RESULT_DRAW:
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if (r == RESULT_DRAW)
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return RESULT_DRAW;
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case RESULT_UNKNOWN:
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if (r == RESULT_UNKNOWN)
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unknownFound = true;
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case RESULT_WIN:
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case RESULT_INVALID:
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break;
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default:
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assert(false);
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}
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}
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return unknownFound ? RESULT_UNKNOWN : RESULT_LOSS;
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}
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@ -23,7 +23,7 @@
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#include "endgame.h"
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#include "pawns.h"
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extern int probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm);
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extern uint32_t probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm);
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namespace {
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