Author: Sune Fischer
Date: 01:33:40 09/14/02
Go up one level in this thread
On September 14, 2002 at 04:10:46, Sune Fischer wrote:
>On September 13, 2002 at 20:28:01, Steffan Westcott wrote:
>
>>
>>Here is some more material for people interested in flood-fill based algorithms,
>>of the ilk I first mentioned in this article :
>>http://www.talkchess.com/forums/1/message.html?251180
>>
>>The following routine determines if a path of set bits in 'path' 8-way connect
>>(ie. king move) any set bit in sq1 with any set bit in sq2 (this is the same as
>>SquaresAreConnected). Also, it will return an array of bitboards showing all
>>possible shortest paths - This is probably best explained by showing an example
>>:
>
>Got it :)
>
>I just thought of another application on the passed pawns.
>This way one doesn't need a 8x64 byte table or calls to firstone().
>I can't say if it's faster than the lookup though, I'll probably
>use it anyway.
>
>//===================================================================
>// find the passed and semi-passed pawns:
>
>BITBOARD WhitePassedPawns(BITBOARD w_pawns,BITBOARD b_pawns) {
> BITBOARD passed=0,tempA,tempB;
> int i=0;
>
> tempA=(w_pawns<<8)&~b_pawns;
> while (tempA) {
> tempB=tempA&rank8;
> i+=8;
> if (tempB) // a pawn has reached the 8th rank
> passed|=tempB>>i; // shift it back to where it originally came from
> tempA=(tempA<<8)&~b_pawns;
> }
> return passed;
>}
>
>//===================================================================
>
>(disclamer: I didn't test it, but you get the idea)
>
>-S.
Actually this may be faster, on 64 bit chips anyway:
while (tempA) {
passed|=(tempA&rank8)>>(i+=8);
tempA=(tempA<<8)&~b_pawns;
}
-S.
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