Author: Uri Blass
Date: 13:03:54 08/22/04
Go up one level in this thread
On August 22, 2004 at 15:54:09, Stuart Cracraft wrote: >On August 22, 2004 at 04:00:53, Uri Blass wrote: > >>On August 21, 2004 at 23:56:48, Stuart Cracraft wrote: >> >>>On August 21, 2004 at 23:39:17, Stuart Cracraft wrote: >>> >>>>There was an error. The right position is: >>>> >>>>[D]5r1k/6p1/1n2Q2p/4p3/8/7P/PP4PK/R1B1q3 w >>>> >>> >>>It takes my program 142M nodes to get the right move for the >>>right reason in 10 minutes. This would be about 1.5 minutes >>>on a more modern PC. >>> >>>I am wondering, specifically, what tricks there are to get it >>>solved faster than this on non-parallel. >>> >>>Stuart >> >>What about check extensions and check in the qsearch? >> >>What is your main problem >>seeing that Qxb6 has negative evaluation or seeing that Bxh6 has better >>evaluation than Qxb6 >> >>In order to see that Qxb6 is losing >>You need to see the following line >> >>1.Qxb6 Rf1 2.Qd8+ Kh7 3.Qd3+ e4 4.Qxx Qh1# >> >>4...Qh1# is move that my qsearch detects so even without check extensions it >>seems to be only 7 plies of search >>2.Qd8+ and 3.Qd3+ are extended by 1 ply so I can see that 1.Qxb6 is losing the >>queen in 5 plies(the evaluation is only slightly behind 0 at this point) >> >>If you want to see that Bxh6 is at least a draw for white then check extensions >>may also help because white has a perpetual check but a lot of checks. >> >>You can use the botvinik extension that is doing partial extensions for >>threating the same piece move after move when the same piece may be also the >>king. >> >>I use the botvinik extension today only for checks. >> >>Uri > >Haven't heard of this one. Sounds interesting. So how do you tell that >you're threatening the same piece move after move? At what point do you >make that decision and grant the partial extension? (fractional same >thing?) > >Stuart In my case I simply extend partial extension when there is more than one consecutive check. If I have check at ply x and x+2 then I extend partial extension(one of the factor that I use to decide how much to extend is the number of legal moves of the side that is in check). I did not write a special code to try it for repeated threat against another piece. Uri
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