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Speedup and simplify pinners and blockers

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To compute dicovered check or pinned pieces we use some bitwise
operators that are not really needed because already accounted for
at the caller site.

For instance in evaluation we compute:

     pos.pinned_pieces(Us) & s

Where pinned_pieces() is:

     st->blockersForKing[c] & pieces(c)

So in this case the & operator with pieces(c) is useless,
given the outer '& s'.

There are many places where we can use the naked blockersForKing[]
instead of the full pinned_pieces() or discovered_check_candidates().

This path is simpler than original and gives around 1% speed up for me.
Also tested for speed by mstembera and snicolet (neutral in both cases).

No functional change.
This commit is contained in:
Marco Costalba
2018-02-27 01:18:33 +01:00
committed by Stéphane Nicolet
parent d438720a1c
commit ad2a0e356e
5 changed files with 30 additions and 31 deletions
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11
src/movegen.cpp
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@@ -135,7 +135,7 @@ namespace {
// if the pawn is not on the same file as the enemy king, because we
// don't generate captures. Note that a possible discovery check
// promotion has been already generated amongst the captures.
Bitboard dcCandidates = pos.discovered_check_candidates();
Bitboard dcCandidates = pos.blockers_for_king(Them);
if (pawnsNotOn7 & dcCandidates)
{
Bitboard dc1 = shift<Up>(pawnsNotOn7 & dcCandidates) & emptySquares & ~file_bb(ksq);
@@ -241,7 +241,7 @@ namespace {
&& !(PseudoAttacks[Pt][from] & target & pos.check_squares(Pt)))
continue;
if (pos.discovered_check_candidates() & from)
if (pos.blockers_for_king(~us) & from)
continue;
}
@@ -336,7 +336,7 @@ ExtMove* generate<QUIET_CHECKS>(const Position& pos, ExtMove* moveList) {
assert(!pos.checkers());
Color us = pos.side_to_move();
Bitboard dc = pos.discovered_check_candidates();
Bitboard dc = pos.blockers_for_king(~us) & pos.pieces(us);
while (dc)
{
@@ -403,8 +403,9 @@ ExtMove* generate<EVASIONS>(const Position& pos, ExtMove* moveList) {
template<>
ExtMove* generate<LEGAL>(const Position& pos, ExtMove* moveList) {
Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
Square ksq = pos.square<KING>(pos.side_to_move());
Color us = pos.side_to_move();
Bitboard pinned = pos.blockers_for_king(us) & pos.pieces(us);
Square ksq = pos.square<KING>(us);
ExtMove* cur = moveList;
moveList = pos.checkers() ? generate<EVASIONS >(pos, moveList)