Author: Robert Hyatt
Date: 08:08:16 07/10/02
Go up one level in this thread
On July 10, 2002 at 08:14:07, José de Jesús García Ruvalcaba wrote: >On July 10, 2002 at 00:47:06, Peter Kappler wrote: > >>On July 09, 2002 at 19:42:37, Robert Hyatt wrote: >> >>>On July 09, 2002 at 17:41:09, Uri Blass wrote: >>> >>>>On July 09, 2002 at 15:25:17, Robert Hyatt wrote: >>>> >>>>>On July 09, 2002 at 13:30:55, Marc van Hal wrote: >>>>> >>>>>>On July 09, 2002 at 02:36:22, Uri Blass wrote: >>>>>> >>>>>>>On July 09, 2002 at 01:34:04, John Reynolds wrote: >>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> If I understand correctly, Diep is using a Supercomputer, shouldn't it be doing >>>>>>>>much better in this tournament, or is it to early to Judge? I mean the Computer >>>>>>>>World Championship ofcourse. >>>>>>> >>>>>>>You did not understand correctly >>>>>>> >>>>>>>see http://www.talkchess.com/forums/1/message.html?238965 >>>>>>> >>>>>>>I also read that in another post that the prices for one hour of the super >>>>>>>computer are very high so I guess that people need to be rich in order to use >>>>>>>the super computer. >>>>>>> >>>>>>>I guess that in order to use the super computer you need a lot of hours of >>>>>>>testing in the super computer to see that things work and if you need to pay >>>>>>>some hundreds of dollars for an hour then it is something that most programmers >>>>>>>cannot even consider and I talk only about 60 cpu's because the prices for 1024 >>>>>>>cpu's are even higher. >>>>>>> >>>>>>>Uri >>>>>> >>>>>> >>>>>>In fact I saw the statements of the WCCC and I ad once was thinking some >>>>>>programs will perform worse if they are just installed on a computer >>>>>>Leading to false results >>>>>>All program with learning have trouble with this only one more then the other. >>>>>>I don't know the reason of this but I do know this from expierince. >>>>>>But in fact it is like a Tournament player who prepared his games and when he >>>>>>has to play the tournament he has to forget everthing he prepared. >>>>>> >>>>>>Marc van Hal >>>>> >>>>> >>>>>There are several issues: >>>>> >>>>>1. using unusual hardware is non-trivial. NUMA machines are one example. >>>>> >>>>>2. Going faster may well cause your eval to misbehave as it is very easy to >>>>>tune an evaluation to a specific search depth and going much deeper or shallower >>>>>can cause some of that tuning to be wrong. >>>> >>>>I agree about the other problems but 2 is not a serious problem. >>> >>> >>>First question, have you _ever_ done this? I have. And I have been burned >>>by it. >>> >>>Second question, did you ever see my comments about how we almost lost (or >>>didn't win) the 1986 WCCC event due to this _very_ problem? If not, I can >>>re-tell the story again. >>> >> >>Yes, please re-tell. >> >> >>>Believe me it _is_ a problem. From someone who developed a chess engine on >>>a machine running 100 nodes per second, and then played on a machine >>>searching 1000 times faster. It can be a _serious_ problem. >>> >>> >>>>Every program that I know is going to play better if you give it 10 hours per >>>>move and not 3 minutes per move. >>>> >>>>Uri >>> >>>Sorry, but you don't know "every program". >>> >> >>Nor did he claim to. >> >>I can't see this happening (weaker play with 200x speedup) unless you have a >>major bug like a sign error in a large positional term like passed-pawn scoring >>or king safety. But that's far beyond what I would consider a "badly-tuned" >>eval. >> >>Actually, forget that, I think the entire eval would have to be backwards for >>that much extra speed to weaken you. I'd gladly invert just my king safety for >>a 200x speedup. ;) >> >>-Peter > >Deeper searches help even if the eval (material and positional) is reversed, the >only requirement is to give mate-scores correctly. >José. What if you have code that evaluates holes in the pawn structure by seeing if they can be used. But to do this, you need some search depth to give the pieces a chance to "hop around" and reach different squares that might exploit the holes. But at shallow depths, the pieces can't reach squares that can use the hole, so you get no penalty for the hole. Now you add a penalty for the hole by itself. And on slow hardware you now make pretty good decisions about when a hole is acceptable and when it is not. And then you run a search to a depth that is twice is deep, so that you suddenly activate _both_ penalties. The penalty for having a hole, _and_ the penalty for having pieces positions that can take advantage of the hole. Suddenly your "good decisions" are no longer good due to extra "paranoia". That is _the_ problem. Any program should play well if it can go deep enough to understand everything. But the eval is a way of plugging long-term oversights with short-sighted eval terms that fix the problem.
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