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Use a Direction enum for Square deltas

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Currently the NORTH/WEST/SOUTH/EAST values are of type Square, but conceptually they are not squares but directions. This patch separates these values into a Direction enum and overloads addition and subtraction to allow adding a Square to a Direction (to get a new Square).

I have also slightly trimmed the possible overloadings to improve type safety. For example, it would normally not make sense to add a Color to a Color or a Piece to a Piece, or to multiply or divide them by an integer. It would also normally not make sense to add a Square to a Square.

This is a non-functional change.
This commit is contained in:
syzygy1
2017-12-04 17:52:31 +01:00
committed by Marco Costalba
parent 2acda1fde3
commit 822695d4d3
10 changed files with 81 additions and 63 deletions
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26
src/bitboard.cpp
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@@ -54,7 +54,7 @@ namespace {
Bitboard RookTable[0x19000]; // To store rook attacks
Bitboard BishopTable[0x1480]; // To store bishop attacks
void init_magics(Bitboard table[], Magic magics[], Square deltas[]);
void init_magics(Bitboard table[], Magic magics[], Direction directions[]);
// bsf_index() returns the index into BSFTable[] to look up the bitscan. Uses
// Matt Taylor's folding for 32 bit case, extended to 64 bit by Kim Walisch.
@@ -188,7 +188,7 @@ void Bitboards::init() {
for (Square s = SQ_A1; s <= SQ_H8; ++s)
for (int i = 0; steps[pt][i]; ++i)
{
Square to = s + Square(c == WHITE ? steps[pt][i] : -steps[pt][i]);
Square to = s + Direction(c == WHITE ? steps[pt][i] : -steps[pt][i]);
if (is_ok(to) && distance(s, to) < 3)
{
@@ -199,11 +199,11 @@ void Bitboards::init() {
}
}
Square RookDeltas[] = { NORTH, EAST, SOUTH, WEST };
Square BishopDeltas[] = { NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST };
Direction RookDirections[] = { NORTH, EAST, SOUTH, WEST };
Direction BishopDirections[] = { NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST };
init_magics(RookTable, RookMagics, RookDeltas);
init_magics(BishopTable, BishopMagics, BishopDeltas);
init_magics(RookTable, RookMagics, RookDirections);
init_magics(BishopTable, BishopMagics, BishopDirections);
for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
{
@@ -225,14 +225,14 @@ void Bitboards::init() {
namespace {
Bitboard sliding_attack(Square deltas[], Square sq, Bitboard occupied) {
Bitboard sliding_attack(Direction directions[], Square sq, Bitboard occupied) {
Bitboard attack = 0;
for (int i = 0; i < 4; ++i)
for (Square s = sq + deltas[i];
is_ok(s) && distance(s, s - deltas[i]) == 1;
s += deltas[i])
for (Square s = sq + directions[i];
is_ok(s) && distance(s, s - directions[i]) == 1;
s += directions[i])
{
attack |= s;
@@ -249,7 +249,7 @@ namespace {
// chessprogramming.wikispaces.com/Magic+Bitboards. In particular, here we
// use the so called "fancy" approach.
void init_magics(Bitboard table[], Magic magics[], Square deltas[]) {
void init_magics(Bitboard table[], Magic magics[], Direction directions[]) {
// Optimal PRNG seeds to pick the correct magics in the shortest time
int seeds[][RANK_NB] = { { 8977, 44560, 54343, 38998, 5731, 95205, 104912, 17020 },
@@ -269,7 +269,7 @@ namespace {
// the number of 1s of the mask. Hence we deduce the size of the shift to
// apply to the 64 or 32 bits word to get the index.
Magic& m = magics[s];
m.mask = sliding_attack(deltas, s, 0) & ~edges;
m.mask = sliding_attack(directions, s, 0) & ~edges;
m.shift = (Is64Bit ? 64 : 32) - popcount(m.mask);
// Set the offset for the attacks table of the square. We have individual
@@ -281,7 +281,7 @@ namespace {
b = size = 0;
do {
occupancy[size] = b;
reference[size] = sliding_attack(deltas, s, b);
reference[size] = sliding_attack(directions, s, b);
if (HasPext)
m.attacks[pext(b, m.mask)] = reference[size];