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Remove popcount16() (official-stockfish#2038)

This is a non-functional simplification / code-style change.

This popcount16 method does nothing but initialize the PopCnt16 arrays.

This can be done in a single bitset line, which is less lines and more clear. Performance for this code is moot.

No functional change.
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protonspring authored and mcostalba committed Mar 10, 2019
1 parent acc47e8 commit b8efa0daac897e1b8f3efb9ca09ec4151492f1e0
Showing with 2 additions and 9 deletions.
  1. +2 −9 src/bitboard.cpp
@@ -19,6 +19,7 @@
*/

#include <algorithm>
#include <bitset>

#include "bitboard.h"
#include "misc.h"
@@ -49,14 +50,6 @@ namespace {
Bitboard BishopTable[0x1480]; // To store bishop attacks

void init_magics(Bitboard table[], Magic magics[], Direction directions[]);

// popcount16() counts the non-zero bits using SWAR-Popcount algorithm
unsigned popcount16(unsigned u) {
u -= (u >> 1) & 0x5555U;
u = ((u >> 2) & 0x3333U) + (u & 0x3333U);
u = ((u >> 4) + u) & 0x0F0FU;
return (u * 0x0101U) >> 8;
}
}


@@ -85,7 +78,7 @@ const std::string Bitboards::pretty(Bitboard b) {
void Bitboards::init() {

for (unsigned i = 0; i < (1 << 16); ++i)
PopCnt16[i] = (uint8_t)popcount16(i);
PopCnt16[i] = std::bitset<16>(i).count();

for (Square s = SQ_A1; s <= SQ_H8; ++s)
SquareBB[s] = (1ULL << s);

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