Author: Gerd Isenberg
Date: 15:49:34 03/25/04
Go up one level in this thread
On March 25, 2004 at 18:30:17, Gerd Isenberg wrote:
>On March 25, 2004 at 08:36:18, Vasik Rajlich wrote:
>
>>On March 24, 2004 at 18:59:02, Gerd Isenberg wrote:
>>
>>>Some minor changes because inOne == inThree is not general enough.
>>>Better to look for no further growing:
>>>if ( (inThree & ~(fromBB|inOne|inTwo)) == 0 && ...
>>>
>>>
>>>// fixed is subset of tabu (may be equal), the set of all own blocked
>>>// and backward pawns.
>>>// tabu may contain enemy pawn attacks which don't terminate the attack ray
>>>
>>>BitBoard getTrappedBishopSquares(BitBoard fixed, BitBoard tabu, int n)
>>>{
>>> BitBoard trappedBishopSquares = 0;
>>> BitBoard potb = ~tabu;
>>> while ( potb ) {
>>> BitBoard fromBB = potb & -potb;
>>> BitBoard inOne = fillBishopAttacks(fromBB, ~fixed) & ~tabu;
>>> BitBoard inTwo = fillBishopAttacks(inOne, ~fixed) & ~tabu;
>>> BitBoard inThree = fillBishopAttacks(inTwo, ~fixed) & ~tabu;
>>> // tag all reachable in up to three moves as done
>>> potb &= ~(fromBB|inOne|inTwo|inThree);
>>> inThree &= ~(fromBB|inOne|inTwo); // growing?
>>> if ( inThree == 0 && popCount(inOne|inTwo) < n )
>>> trappedBishopSquares |= (fromBB|inOne|inTwo);
>>> }
>>> return trappedBishopSquares;
>>>}
>>>
>>>popCount > n considers the whole fill area reachable in two moves.
>>
>>Gerd,
>>
>>thanks, I'll try it in Rybka.
>
>I'll too in IsiChessXMM ;-)
>
>As Sune already mentioned,
>
>fillBishopOccluded(fromBB, ~tabu)
>
>is a bit faster (one 64-bit shift,two ands less for each of four directions)
>than
>
>fillBishopAttacks(fromBB, ~tabu) & ~tabu;
>
>But the latter has the option, to distinguish between mechanical own fixed pawns
>(or defended enemy pawns) and additional enemy pawn controls ...
>
>fillBishopAttacks(fromBB, ~fixed) & ~tabu;
oups wrong! fillOccluded is still faster here than getAttacks and may even
supplied with an additional masking out of enemy pawn attacks.
fillBishopOccluded(fromBB, ~fixed) & ~tabu;
// fixed is subset of taboo (may be equal), the set of all own blocked
// and backward pawns.
// tabu may contain enemy pawn attacks which don't terminate the attack ray
BitBoard getTrappedBishopSquares(BitBoard fixed, BitBoard taboo, int n)
{
BitBoard trappedBishopSquares = 0;
BitBoard potb = ~taboo;
while ( potb ) {
BitBoard fromBB = potb & -potb;
BitBoard inOne = fillBishopOccluded(fromBB, ~fixed) & ~taboo;
BitBoard inTwo = fillBishopOccluded(inOne, ~fixed) & ~taboo;
BitBoard inThree = fillBishopOccluded(inTwo, ~fixed) & ~taboo;
// tag all reachable in up to three moves as done
potb &= ~inThree;
inThree &= ~inTwo; // growing?
if ( inThree == 0 && popCount(inTwo) < n )
trappedBishopSquares |= inTwo;
}
return trappedBishopSquares;
}
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