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kpk.c
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/*----------------------------------------------------------------------+
| |
| kpk.c -- pretty fast KPK endgame table generator |
| |
+----------------------------------------------------------------------*/
/*
* Copyright (C) 2015-2016, Marcel van Kervinck
* All rights reserved
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/*----------------------------------------------------------------------+
| Includes |
+----------------------------------------------------------------------*/
// C standard
#include <stdint.h>
#include <stdlib.h>
// Own interface
#include "kpk.h"
/*----------------------------------------------------------------------+
| Definitions |
+----------------------------------------------------------------------*/
enum { N = a2-a1, S = -N, E = b1-a1, W = -E }; // Derived geometry
#define inPawnZone(square) (rank(square)!=rank1 && rank(square)!=rank8)
#define conflict(wKing,wPawn,bKing) (wKing==wPawn || wPawn==bKing || wKing==bKing)
#define dist(a,b) (abs(file(a)-file(b)) | abs(rank(a)-rank(b))) // logical-or as max()
#define wInCheck(wKing,wPawn,bKing) (dist(wKing,bKing)==1)
#define bInCheck(wKing,wPawn,bKing) (dist(wKing,bKing)==1 \
|| (file(wPawn)!=fileA && wPawn+N+W==bKing) \
|| (file(wPawn)!=fileH && wPawn+N+E==bKing))
// Square set macros (no need to adapt these to the specific geometry)
#define bit(i) (1ULL << (i))
#define mask 0x0101010101010101ULL
#define allW(set) ((set) >> 8)
#define allE(set) ((set) << 8)
#define allS(set) (((set) & ~mask) >> 1)
#define allN(set) (((set) << 1) & ~mask)
#define allKing(set) (allW(allN(set)) | allN(set) | allE(allN(set)) \
| allW(set) | allE(set) \
| allW(allS(set)) | allS(set) | allE(allS(set)))
#define arrayLen(a) ((int) (sizeof(a) / sizeof((a)[0])))
enum { white, black };
#define kpIndex(wKing,wPawn) (((wKing) << 5) + (file(wPawn) << 3) + rank(wPawn))
#define wKingSquare(ix) ((ix)>>5)
#define wPawnSquare(ix) square(((ix)>>3)&3, (ix)&7)
/*----------------------------------------------------------------------+
| Data |
+----------------------------------------------------------------------*/
static uint64_t kpkTable[2][64*32];
static const int kingSteps[] = { N+W, N, N+E, W, E, S+W, S, S+E };
/*----------------------------------------------------------------------+
| Functions |
+----------------------------------------------------------------------*/
int kpkProbe(int side, int wKing, int wPawn, int bKing)
{
if (!kpkTable[0][1]) kpkGenerate();
if (file(wPawn) >= 4) {
wKing ^= square(7, 0);
wPawn ^= square(7, 0);
bKing ^= square(7, 0);
}
int ix = kpIndex(wKing, wPawn);
int bit = (kpkTable[side][ix] >> bKing) & 1;
return (side == white) ? bit : -bit;
}
int kpkGenerate(void)
{
uint64_t valid[ arrayLen(kpkTable[0]) ];
for (int ix=0; ix<arrayLen(kpkTable[0]); ix++) {
int wKing = wKingSquare(ix), wPawn = wPawnSquare(ix);
// Positions after winning pawn promotion (we can ignore stalemate here)
if (rank(wPawn) == rank8 && wKing != wPawn) {
uint64_t lost = ~allKing(bit(wKing)) & ~bit(wKing) & ~bit(wPawn);
if (dist(wKing, wPawn) > 1)
lost &= ~allKing(bit(wPawn));
kpkTable[black][ix] = lost;
}
// Valid positions after black move, pawn capture allowed
valid[ix] = ~allKing(bit(wKing));
if (rank(wPawn) != rank8 && file(wPawn) != fileA) valid[ix] &= ~bit(wPawn+N+W);
if (rank(wPawn) != rank8 && file(wPawn) != fileH) valid[ix] &= ~bit(wPawn+N+E);
}
int changed;
do {
for (int ix=0; ix<arrayLen(kpkTable[0]); ix++) {
int wKing = wKingSquare(ix), wPawn = wPawnSquare(ix);
if (!inPawnZone(wPawn))
continue;
// White king moves
uint64_t won = 0;
for (int i=0; i<arrayLen(kingSteps); i++) {
int to = wKing + kingSteps[i];
int jx = ix + kpIndex(kingSteps[i], 0);
if (dist(wKing, to & 63) == 1 && to != wPawn)
won |= kpkTable[black][jx] & ~allKing(bit(to));
}
// White pawn moves
if (wPawn+N != wKing) {
won |= kpkTable[black][ix+kpIndex(0,N)] & ~bit(wPawn+N);
if (rank(wPawn) == rank2 && wPawn+N+N != wKing)
won |= kpkTable[black][ix+kpIndex(0,N+N)]
& ~bit(wPawn+N) & ~bit(wPawn+N+N);
}
kpkTable[white][ix] = won & ~bit(wPawn);
}
changed = 0;
for (int ix=0; ix<arrayLen(kpkTable[0]); ix++) {
if (!inPawnZone(wPawnSquare(ix)))
continue;
// Black king moves
uint64_t isBad = kpkTable[white][ix] | ~valid[ix];
uint64_t canDraw = allKing(~isBad);
uint64_t hasMoves = allKing(valid[ix]);
uint64_t lost = hasMoves & ~canDraw;
changed += (kpkTable[black][ix] != lost);
kpkTable[black][ix] = lost;
}
} while (changed);
return sizeof kpkTable;
}
int kpkSelfCheck(void)
{
int counts[] = { // As given by Steven J. Edwards (1996):
163328 / 2, 168024 / 2, // - Legal positions per side
124960 / 2, 97604 / 2 // - Non-draw positions per side
};
for (int ix=0; ix<arrayLen(kpkTable[0]); ix++) {
int wKing = wKingSquare(ix), wPawn = wPawnSquare(ix);
for (int bKing=0; bKing<boardSize; bKing++) {
if (!inPawnZone(wPawn) || conflict(wKing, wPawn, bKing))
continue;
counts[0] -= !bInCheck(wKing, wPawn, bKing);
counts[1] -= !wInCheck(wKing, wPawn, bKing);
counts[2] -= !bInCheck(wKing, wPawn, bKing) && ((kpkTable[white][ix] >> bKing) & 1);
counts[3] -= !wInCheck(wKing, wPawn, bKing) && ((kpkTable[black][ix] >> bKing) & 1);
}
}
return !counts[0] && !counts[1] && !counts[2] && !counts[3];
}
/*----------------------------------------------------------------------+
| |
+----------------------------------------------------------------------*/