Author: Vincent Diepeveen
Date: 05:46:10 08/08/00
Go up one level in this thread
On August 07, 2000 at 05:28:00, Andrew Williams wrote: >On August 06, 2000 at 20:15:46, Vincent Diepeveen wrote: > >>On August 06, 2000 at 16:48:16, Andrew Williams wrote: >> >>>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. >> >>DIEP uses hell of a lot nodes more if i use MTD. >> > >It's not clear from this if you're saying you've tried it and you've got >the figures, or if you are speculating that DIEP would be worse with MTD? > It is using a lot more nodes using MTD. Didn't i clearly write that down? Note that DIEP using PVS can better use -infinite,infinite as root window than using a small window. In the positions as described: tough positions, i figured out that in case of fail lows (even if they're small) that it needs a lot more nodes. In case of fail highs it might save nodes of course. That's simply not interesting basically. Positions that fail high i give more search time anyway, and you search in that kind of positions already deeper anyway. >Andrew > > >>A pawn in DIEP is 1000 points worth. >> >>So correct me if i'm wrong: >> >>If this iteration i'm at +0.300 next iteration i'm at +0.600 with PVS, >>then how many researches do i need with MTD? >> >>>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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