Author: Robert Hyatt
Date: 18:25:45 12/20/99
Go up one level in this thread
On December 20, 1999 at 14:24:04, James Swafford wrote:
>There is no such thing as a position with two legal ep captures.
>The ep flag is cleared immediately, so your code is crap.
Wrong. put a white pawn on d5 and f5. Black plays e5. White now has
_two_ possible enpassant captures, either dxe6 or fxe6.
>
>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.
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