hash.cpp

#include "hash.h"

HElem HTable[HASH_SIZE];

ull zobristPieces[14][64], zobristPlayer, zobristCastling[4], zobristEnPassant[64];

// Initialize the hashing numbers and other hash initialization stuff
void InitHash()
{
	for (int i=0; i<14; ++i)
		for (int j=0; j<64; ++j)
			zobristPieces[i][j] = GetRand64();
	zobristPlayer = GetRand64();
	for (int i=0; i<4; ++i)
		zobristCastling[i] = GetRand64();
	for (int i=0; i<64; ++i)
		zobristEnPassant[i] = GetRand64();
}

// Calculate a Zorbist Key from a given board
// should not be used very often
// the key should be maintained in the Board class with MakeMove
ull GetZobristKey(const Board &board)
{
	ull key=0;

	// white pieces
	for (int i=PAWN_W; i<=KING_W; ++i) {
		ull aux = board.bb[i];
		for (int pp = LSBi(aux); pp != 64; pp = LSBi(aux))
			key ^= zobristPieces[i][pp];
	}

	// black pieces
	for (int i=PAWN_B; i<=KING_B; ++i) {
		ull aux = board.bb[i];
		for (int pp = LSBi(aux); pp != 64; pp = LSBi(aux))
			key ^= zobristPieces[i][pp];
	}

	// castling flags
	ull aux = board.castling;
	for (int pp = LSBi(aux); pp != 64; pp = LSBi(aux))
		key ^= zobristCastling[pp];

	// enPassant
	key ^= zobristEnPassant[board.enPassant];

	// who moves
	if (board.player) key ^= zobristPlayer;

	return key;
}

ull GetPawnZobristKey(const Board &board)
{
	ull aux, key=0;
	aux = board.bb[PAWN_W];
	for (int pp = LSBi(aux); pp != 64; pp = LSBi(aux))
		key ^= zobristPieces[13][pp];
	aux = board.bb[PAWN_B];
	for (int pp = LSBi(aux); pp != 64; pp = LSBi(aux))
		key ^= zobristPieces[13][pp];
	return key;
}

void SetHElem(const int index, const HElem elem)
{
	// Replace key if table position is empty OR
	// if number of pieces in stored table is greater or equal to new elem OR
	// if calculated depth in table is less than the new elem depth

	if (HTable[index].npiece == 0 ||
		(HTable[index].npiece && HTable[index].npiece >= elem.npiece) ||
		(HTable[index].depth < elem.depth)) {

		HTable[index] = elem;
	}
}