Author: José Carlos
Date: 09:45:05 09/11/04
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On September 11, 2004 at 12:04:23, Aivaras Juzvikas wrote: >On September 11, 2004 at 11:47:35, José Carlos wrote: > >>On September 10, 2004 at 21:35:58, Stuart Cracraft wrote: >> >>>I read, somewhere, and I forget who, about >>>if 1 legal move, extend 2 ply, >>>2 or more legal moves, then 1 ply. >>>Anyone have any stats on the effects >>>on play of the above instead of >>>always extend 1 legal move. Does it >>>blow up? >> >> >> I guess you read it in Ed's programming page about Rebel. He does that in >>qsearch, and regarding checking moves generation. >> I tried his idea in my private program and it didn't work for me. It generated >>too many nodes, but I probably did something wrong. >> >> >>>How do people get around the cost >>>of determining that there is only >>>1 legal move? >> >> >> If you're in check (you know it before generating moves) you can use a special >>move generator that generates only escapes from check (capturing checking piece, >>moving the king, putting a piece in between...). In that case, you know in >>advance the number of legal moves. > >how about puttin a piece in between which uncovers attack on king by another >piece?this legal move generator doesnt look so simple to me somehow, am i >missing smth? No, you aren't. It's not simple, but it's simpler that I had thought before trying. For your uncovered attack case, I calculate pinned pieces (easy with bitboards) and then I don't allow a pinned piece to cover a check. There're also other particular cases, like en passant, promotions, double checks... Once you think about them all and draw the algorithm, implementing it is easy. José C. >> >> José C. >> >> >>>For me, that's an expensive operation >>>involving usually dozens of makemove/unmakemove's >>>with a test to see if the king is attacked, >>>at every single node, before doing the search >>>of the 1 move with the increased depth. >>> >>>Only rarely is it just 1 legal move to get >>>out of check. But the determination of that >>>is not rare. It has to be done for every >>>sweep of the moves at each node. >>> >>>Thanks, >>> >>>Stuart
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