Author: Gian-Carlo Pascutto
Date: 02:35:37 09/12/04
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On September 10, 2004 at 21:35:58, Stuart Cracraft wrote: >How do people get around the cost >of determining that there is only >1 legal move? > >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. I didn't see anyone hint at this rather simple solution which, in my experience, works perfectly fine: 1) if not in check, assume you have > 1 legal move and don't bother testing anything at all 2) if in check, just do the slow check of all moves. You can stop as soon as you see 2 legal moves, so generally only a few moves have to be tried. Case (2) is seldom enough that you should not slow down noticeably at all because of this. -- GCP
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