#include "bitboard.h"
#include "bitcount.h"
+#include "misc.h"
#include "rkiss.h"
CACHE_LINE_ALIGNMENT
namespace {
+ // De Bruijn sequences. See chessprogramming.wikispaces.com/BitScan
+ const uint64_t DeBruijn_64 = 0x218A392CD3D5DBFULL;
+ const uint32_t DeBruijn_32 = 0x783A9B23;
+
CACHE_LINE_ALIGNMENT
int BSFTable[64];
Bitboard masks[], unsigned shifts[], Square deltas[], Fn index);
}
-/// first_1() finds the least significant nonzero bit in a nonzero bitboard.
-/// pop_1st_bit() finds and clears the least significant nonzero bit in a
-/// nonzero bitboard.
-
-#if defined(IS_64BIT) && !defined(USE_BSFQ)
+/// lsb()/msb() finds the least/most significant bit in a nonzero bitboard.
+/// pop_lsb() finds and clears the least significant bit in a nonzero bitboard.
-Square first_1(Bitboard b) {
- return Square(BSFTable[((b & -b) * 0x218A392CD3D5DBFULL) >> 58]);
-}
+#if !defined(USE_BSFQ)
-Square pop_1st_bit(Bitboard* b) {
- Bitboard bb = *b;
- *b &= (*b - 1);
- return Square(BSFTable[((bb & -bb) * 0x218A392CD3D5DBFULL) >> 58]);
-}
+Square lsb(Bitboard b) {
-#elif !defined(USE_BSFQ)
+ if (Is64Bit)
+ return Square(BSFTable[((b & -b) * DeBruijn_64) >> 58]);
-Square first_1(Bitboard b) {
b ^= (b - 1);
uint32_t fold = unsigned(b) ^ unsigned(b >> 32);
- return Square(BSFTable[(fold * 0x783A9B23) >> 26]);
+ return Square(BSFTable[(fold * DeBruijn_32) >> 26]);
}
-Square pop_1st_bit(Bitboard* b) {
+Square pop_lsb(Bitboard* b) {
Bitboard bb = *b;
*b = bb & (bb - 1);
+
+ if (Is64Bit)
+ return Square(BSFTable[((bb & -bb) * DeBruijn_64) >> 58]);
+
bb ^= (bb - 1);
uint32_t fold = unsigned(bb) ^ unsigned(bb >> 32);
- return Square(BSFTable[(fold * 0x783A9B23) >> 26]);
+ return Square(BSFTable[(fold * DeBruijn_32) >> 26]);
}
-Square last_1(Bitboard b) {
+Square msb(Bitboard b) {
unsigned b32;
int result = 0;
void Bitboards::print(Bitboard b) {
+ sync_cout;
+
for (Rank rank = RANK_8; rank >= RANK_1; rank--)
{
std::cout << "+---+---+---+---+---+---+---+---+" << '\n';
for (File file = FILE_A; file <= FILE_H; file++)
- std::cout << "| " << (b & make_square(file, rank) ? "X " : " ");
+ std::cout << "| " << (b & (file | rank) ? "X " : " ");
std::cout << "|\n";
}
- std::cout << "+---+---+---+---+---+---+---+---+" << std::endl;
+ std::cout << "+---+---+---+---+---+---+---+---+" << sync_endl;
}
Bitboard b = 1ULL << i;
b ^= b - 1;
b ^= b >> 32;
- BSFTable[(uint32_t)(b * 0x783A9B23) >> 26] = i;
+ BSFTable[(uint32_t)(b * DeBruijn_32) >> 26] = i;
}
else
- BSFTable[((1ULL << i) * 0x218A392CD3D5DBFULL) >> 58] = i;
+ BSFTable[((1ULL << i) * DeBruijn_64) >> 58] = i;
int steps[][9] = { {}, { 7, 9 }, { 17, 15, 10, 6, -6, -10, -15, -17 },
{}, {}, {}, { 9, 7, -7, -9, 8, 1, -1, -8 } };