Author: José Carlos
Date: 10:36:46 09/12/04
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Hi Scott, [...] >I thought this is what he was talking about too. My take on Ed's page is that >he extends the depth in qsearch at which he will consider checking moves by 2 >ply when a side in check only has 1 legal way out. This is _way_ different than >extending by 2 ply in the main search -- that would cause a node explosion >especially if you also extend on the checking move! > >I tried Ed's idea in qsearch too and found the same thing as you, José. Then I >decided to try to restrict where I did it... 1. to only do it when the guy in >check's king safety score indicated that he was in some danger and 2. to only do >it when the side in check has not had a chance to stand pat yet. Oh and 3. I >don't do it past a certain number of plies from the root... something like >iterate_depth * 3 or so. This keeps it under control but it doesn't solve Ed's >tricky mate in 30 by checking a million times with the knight position (Note: >Stuart: that is the position you posted last week, so you're on the right track >for solving it!) I understand that you're talking about in-check positions, not generate-checks positions, right? There're are some problems in both types of positions, but I think it's generate-checks positions that blow up the tree. In these positions, you need hashing (as Ed says in other post) and I also found useful to try some restrictions, for example not trying checks with SEE < 0 (Tord's idea), disable it in some endings, like queen endings, not trying checks in clearly lost positions, and some other ideas that I don't remember now. [...] >This is what I do too. Write a legal move generator and only do it when you're >in check. Then you can detect stuff like: 1. One legal move, 2. In check by >more than one piece, 3. No legal king moves etc... I extend to some degree on >all of these. Interesting. I also detected all of those but didn't extend. All in all, I wasn't using fractional extensions there. If I continue with chess programming some day, I'll try those extensions. José C.
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