Author: James Swafford
Date: 11:24:04 12/20/99
Go up one level in this thread
There is no such thing as a position with two legal ep captures.
The ep flag is cleared immediately, so your code is crap.
Next time, email me. You know the address; we just exchanged
emails last week. There's a link on my site.
--
James
On December 20, 1999 at 12:57:08, Nicolas Carrasco wrote:
>Dear Guys,
>
>While I started studying how to write a Bitboard chess engine I read “Galahad
>Chess Engine” move generator from James F. Swafford publicated on:
>http://members.xoom.com/jswaff/chessprg/ at Move Generation section.
>NOTE: At the end you will have a link to download the move-gen.
>
>I wrote him several e-mails but never recived a reply.
>
>To generate the EP captures he does this that I think is wrong because he forget
>a position with two possible EP captures.
>
> if (posptr->epsquare<64) {
> to_map=bpmoves[posptr->epsquare]&posptr->whitepawns;
> if (to_map) {
> from_sq=LSB(to_map);
> m->m.b.from=from_sq;
> m->m.b.to=posptr->epsquare;
> m->m.b.promote=0;
> m->m.b.bits=21;
> m->score=0;
> m++;
> }
> }
>
>And nothing else for EP captures.
>
>I think the correct way is:
>
> if (posptr->epsquare<64) {
> to_map=bpmoves[posptr->epsquare]&posptr->whitepawns;
> while (to_map) {
> from_sq=LSB(to_map);
> to_map^=mask[to_sq];
> m->m.b.from=from_sq;
> m->m.b.to=posptr->epsquare;
> m->m.b.promote=0;
> m->m.b.bits=21;
> m->score=0;
> m++;
> }
> }
>
>Or:
>
> if (posptr->epsquare<64) {
> to_map=bpmoves[posptr->epsquare]&posptr->whitepawns;
> if (to_map) {
> from_sq=LSB(to_map);
> to_map^=mask[to_sq];
> m->m.b.from=from_sq;
> m->m.b.to=posptr->epsquare;
> m->m.b.promote=0;
> m->m.b.bits=21;
> m->score=0;
> m++;
> if (to_map) {
> from_sq=LSB(to_map);
> m->m.b.from=from_sq;
> m->m.b.to=posptr->epsquare;
> m->m.b.promote=0;
> m->m.b.bits=21;
> m->score=0;
> m++;
> }
> }
> }
>
>To James: Can you tell me your usual e-mail address?
>
>Thanks in advance and good luck.
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.