Author: Robert Hyatt
Date: 21:01:02 09/30/04
Go up one level in this thread
On September 30, 2004 at 23:02:42, Uri Blass wrote: >On September 30, 2004 at 18:19:01, Robert Hyatt wrote: > >>On September 29, 2004 at 19:54:50, Stuart Cracraft wrote: >> >>>On September 29, 2004 at 18:34:40, Uri Blass wrote: >>> >>>>On September 29, 2004 at 18:20:45, martin fierz wrote: >>>> >>>>>On September 29, 2004 at 16:21:43, Uri Blass wrote: >>>>> >>>>> >>>>>>I think that it is clear that extending every nate threat by a full ply will >>>>>>blow your search. >>>>>> >>>>>>If you do not use partial extensions then I suggest that you do not extend mate >>>>>>threats unless you have some conditions to extend them only near the root and >>>>>>not every where. >>>>>> >>>>>>Uri >>>>> >>>>>i extend mate threat by a full ply always. and my search isn't blowing up, at >>>>>least not that i notice. then again, WAC 141 shows some strange behavior with my >>>>>latest version: >>>>> >>>>>MUSE 0.89.10 UCI 30 MB: >>>>> >>>>> 1 00:00 -1.65 Kg2g1 >>>>> 2+ 00:00 -2.36 Kg2f1 >>>>> 2 00:00 -2.36 Kg2f1 Nf4d3 >>>>> 3 00:00 -1.22 Kg2f1 Re8b8 Kf1e1 >>>>> 4 00:00 -2.13 Kg2f1 Kg8h7 Bb3d1 Nf4d3 >>>>> 5 00:00 -2.16 Kg2f1 Re8e2 Kf1g1 Nf4d5 Kg1f1 >>>>> 6+ 00:00 -1.66 Qc1xf4 >>>>> 6 01:24 M6 Qc1xf4 Bd6xf4 Rh4xh5 g6xh5 Rh1xh5 Bf4h6 Rh5xh6 >>>>> >>>>>it sees Qxf4 after 0 seconds (this is on a slowly 1.4GHz P4), but needs a very >>>>>long time to resolve it. but at least it sees Qxf4 in 0 seconds :-) >>>>> >>>>>cheers >>>>> martin >>>> >>>>If you extend also checks by a full ply then there are cases when there is a >>>>long sequence >>>>check ,escape threat mate,check,escape threat mate and it means that you may >>>>have big problems to search deep in position when one side threats mate but the >>>>opponenthas a lot of checks because he tries to do perpetual checks. >>>> >>>>You can easily search some lines to more than 100 plies at small depth and I do >>>>not believe that it is a good idea. >>>> >>>>Uri >>>> >>>> >>>>Uri >>> >>>This is very useful. Okay, in main search I can just start off with >>>revaluing check extension to 0.75 instead of 1 but I'd expect that >>>since I have few extensions, very few checks would be searched. >>>How would you handle reducing check extension value in such an >>>arrangement. >>> >>>Also, my quiescence search always investigates all check evasions >>>to any depth. Should I be doing that? >> >>Absolutely not. IE you capture at first q-search ply where you can also stand >>pat. Your opponent captures at the next ply and you try all moves to get out of >>check and eventually find a deep mate. It isn't forced as you can just stand >>pat at the first capture and all that searching was wasted... > >The searching was not wasted unless standing pat is better because you learned >that the capture is not good. >Let take 2 examples > >[D]r5k1/6pp/4b3/7q/8/4R3/5PPP/N2B2K1 w - - 0 1 > >If you search check evasion you can find that BxQ is bad and return the stand >pat score that is bad for white. > >[D]r5k1/6pp/4b3/7p/8/4R3/5PPP/N2B2K1 w - - 0 1 > >In this case of course you do not search after Bxh5 RxN+ because there is no >check evasion to do the score above alpha and alpha in the beginning was the >standpat score or something higher. > >Uri I've said this hundreds of times... I don't want my q-search to deal with that at all. Whether it does only captures or captures+checks+check evasions is _still_ way too selective. I can construct just as many positions where the best move is not a capture or a check, and the q-search returns the wrong value. So I prefer to reduce the q-search to a minumum and hopefully let my normal search go a ply or two deeper and handle that stuff correctly by looking at everything, not just a very selective subset of moves... My own personal preference of course... but WAC141 gives me absolutely no probelms either...
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