Author: Andrew Williams
Date: 13:48:16 08/06/00
Go up one level in this thread
On August 06, 2000 at 16:36:15, Vincent Diepeveen wrote: >Show me an MTD program that uses less nodes a ply as DIEP does. > I've no idea if Diep uses fewer nodes than others. However, even if it does, would you say this is due purely to the superiority of PVS over MTD? Surely your evaluation is different to other programs too? The point I want to make is that it's not helpful to Larry (or anyone anyone else) if you just say "MTD(f) sux! PVS rox!" UNLESS you provide some rationale for your opinion. Andrew PS Your "there are no commercial programs using MTD" argument doesn't really represent a rationale, in my opinion. >What diep is doing is very simple in search: > > PVS (starting with -infinite) > check extensions > checks in qsearch > nullmove R=3 > no other crap. no pruning. Perhaps at WMCC i prune a bit, > but that's because against computers playing is different. > > Yet i'm missing programs using less nodes a ply with MTD. > I"m missing *any* deep searching program that uses MTD actually. > >On August 06, 2000 at 10:31:58, An > > > >drew Williams wrote: > >>On August 06, 2000 at 09:38:18, Vincent Diepeveen wrote: >> >>>On August 05, 2000 at 11:37:01, Larry Griffiths wrote: >>> >>>>Which Algorithm is considered the best now-adays. >>> >>>Depends upon what kind of program you make. >>> >>>If you have an evaluation function that has patterns which all deliver >>>very small penalties and bonusses, from which the summation also adds up >>>to a near to material only evaluation, then MTD is an interesting >>>alternative. >> >>PostModernist uses MTD. It would be incorrect to describe its evaluation >>as being "near to material-only". This opinion (on MTD) is one that Vincent >>has expounded before, without much in the way of supporting evidence. >> >>> >>>If the evaluation function is either big, using a pawn as being >>>worth 1000 points instead of 1 point, the eval is huge, or having high scores >>>for for example king safety and or passers, >>>then you have only 1 option that outperforms >>>*anything*, and that's nullwindow search also called principal variation >>>search which is pretty easy to implement. >>> >>>Usually at the start of your program MTD looks interesting, if your >>>program gets better (more knowledge in eval, less bugs in search and >>>better move ordering), then PVS usually outperforms anything. >>> >> >>I don't think there is any evidence anywhere that supports Vincent's opinion >>about MTD. Just stating an opinion does not make it true :-) >> >>>My advice is to start with PVS and not look to the rest. >>> >>>>NegaScout? MTD? PVS? Others? I am looking to implement one of the best search >>>>type algorithms in my program. I would like to get it into the 2000 rated range >>>>as this has been my lifetime goal. Then, maybe install winboard or something so >>>>it can compete against other programs to get a rating. >>>>I dont like MTD as it seems to be complex. >>>> >>>>Larry. >> >>My advice would be to get a straight alpha-beta search working, starting >>with bounds of -inf..+inf. This won't be terribly competitive, but you >>can use it as a stable reference when you move on to more sophisticated >>approaches. When you're happy with your alpha-beta search, try implementing >>an aspiration-search, which is like alpha-beta except that you start with >>bounds of score-50 .. score+50, where score is the value returned from the >>previous iteration. You will need to provide some way of handling the case >>where the returned score from *this* search falls outside this "window". >>Once you've got your aspiration search working properly, you'll be in a >>strong position to decide where you want to go with your program. >> >>Above all, have fun with your program! >> >>Andrew Williams
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