Author: Matthew Hull
Date: 09:25:36 05/05/04
Go up one level in this thread
On May 05, 2004 at 12:21:31, Robert Hyatt wrote: >On May 05, 2004 at 12:12:59, Matthew Hull wrote: > >>On May 05, 2004 at 11:37:50, Robert Hyatt wrote: >> >>>On May 05, 2004 at 10:25:23, Matthew Hull wrote: >>> >>>>On May 05, 2004 at 04:44:19, martin fierz wrote: >>>> >>>>>On May 04, 2004 at 21:06:30, Robert Hyatt wrote: >>>>> >>>>>>On May 04, 2004 at 18:21:07, martin fierz wrote: >>>>>> >>>>>>>On May 04, 2004 at 13:44:21, Robert Hyatt wrote: >>>>>>> >>>>>>>>On May 04, 2004 at 10:49:42, martin fierz wrote: >>>>>>>> >>>>>>>>>On May 04, 2004 at 07:32:01, Rolf Tueschen wrote: >>>>>>>>> >>>>>>>>>>On May 04, 2004 at 07:11:15, martin fierz wrote: >>>>>>>>>> >>>>>>>>>>>On May 03, 2004 at 22:50:58, Robert Hyatt wrote: >>>>>>>>>>> >>>>>>>>>>>>If you recall, I _have_ given some error estimates in the past. Remember the >>>>>>>>>>>>wildly varying speedup numbers I showed you the first time this issue came up? >>>>>>>>>>> >>>>>>>>>>>i recall that you gave wildly varying speedup numbers, and an explanation for >>>>>>>>>>>why this happens. i don't recall a real error estimate, but that can be either >>>>>>>>>>>because >>>>>>>>>>>-> you gave one and i didn't see it >>>>>>>>>>>-> you gave one, i saw it and forgot >>>>>>>>>>>-> you didn't give one at all >>>>>>>>>>> >>>>>>>>>>>so... what kind of numbers would you give if you were pressed? >>>>>>>>>> >>>>>>>>>> >>>>>>>>>>Isn't it impolite to imply the third option if Bob JUST said that he did give >>>>>>>>>>some? >>>>>>>>> >>>>>>>>>no - asking questions always has to be allowed among scientists. forbidding to >>>>>>>>>ask questions is the hallmark of religious fanatics and fascists... but i >>>>>>>>>digress :-) >>>>>>>>>bob says he gave numbers, which he did. but IIRC, he never gave an error >>>>>>>>>estimate. so i am allowed to ask for it, and it is not at all impolite to do so. >>>>>>>>>what he did show is the speedup in about 30 different positions, which could >>>>>>>>>vary wildly depending on the position. >>>>>>>>> >>>>>>>>>i don't know why you think you have to stand up and defend bob every time >>>>>>>>>somebody says something about him you don't like. just leave that up to him. he >>>>>>>>>can take it :-) >>>>>>>>> >>>>>>>>>cheers >>>>>>>>> martin >>>>>>>> >>>>>>>> >>>>>>>>I wasn't offended. I hope my answer was ok. >>>>>>> >>>>>>>i didn't think you'd be offended, and your answer was ok, but...why don't you >>>>>>>take N (preferably N>>30...) positions and compute the standard deviation of >>>>>>>your speedup numbers, and the standard deviation of the average speedup? you can >>>>>>>still discuss the meaning of this, but at least you have an error margin you can >>>>>>>attach to your speedup. i don't see anything wrong with that!? even if the >>>>>>>probability distribution is obviously not a normal distribution, you can >>>>>>>probably approximate it as such, and get an idea of it's width from these >>>>>>>numbers. >>>>>>> >>>>>>>>This is not an easy question to deal with. >>>>>>> >>>>>>>>IE if you take the standard deviation of a set of random numbers between >>>>>>>>0 and N what do you get? That is what the speedup numbers look like for some >>>>>>>>positions. For others the speedup is a near-perfect constant value. Add some >>>>>>>>perfect constants plus some randomly distributed values and exactly what does >>>>>>>>the SD show? :) >>>>>>> >>>>>>>i don't quite understand your question. if you take enough positions, then you >>>>>>>will get something sensible, i would think. if you doubt this, you can take e.g. >>>>>>>10'000 sequential positions from crafty's ICC log, and bunch them together in >>>>>>>groups of 1000, and compute average speedup + stdev-of-average-speedup for each >>>>>>>of the bunches. i can't imagine that you get 10 wildly differing values, as your >>>>>>>statement above suggests. >>>>>>> >>>>>>>cheers >>>>>>> martin >>>>>> >>>>>> >>>>>>It isn't so easy to get speedup. IE how would I take a position that took X >>>>>>seconds with 2 or 4 cpus and compute the 1 cpu time? Think about it carefully >>>>>>and you will see the problem. How to get the 1-cpu test case to have a properly >>>>>>loaded hash table, killer move table, history table, etc, before starting the >>>>>>search??? >>>>> >>>>>i don't understand this part at all. run the exact same test on a 1 CPU machine, >>>>>and then on an N-CPU machine. >>>>>the reason i don't understand this at all is that all the details you are >>>>>talking about are irrelevant. i want to know what happens if i run the same test >>>>>positions on a 1 CPU box or on a N CPU box. this is easy to answer, because it >>>>>can be determined experimentally. whether or not there are philosophical issues >>>>>as those you raise above can be discussed, but it doesn't stop you from getting >>>>>your number... >>>>> >>>>> >>>>>>The best bet is to take N positions where N is large. But then that is not the >>>>>>same as what happens in real games where the positions are connected via info >>>>>>passed from search to search in the hash table. >>>>> >>>>>not true if you use 1000 positions from crafty's ICC log file, where the exact >>>>>same thing happens, because these are also positions from real games, connected >>>>>to each other. >>>> >>>> >>>>The only way I can see how your idea would work is if crafty played a series of >>>>games searching to a fixed depth with a single processor. Then take the >>>>positions from those games and set them up in the order they occurred and time >>>>crafty's response to those positions to the same depth, but with 2 processors, >>>>then do it all over again with 3 processors, etc. That way for each run, the >>>>effects of cache relavency are not lost as would be the case in disconnected >>>>test set positions. >>>> >>>>Then you might have an idea of an expected speedup in actual games, rather than >>>>from disconnected test positions. >>>> >>>>That is a much more involved and time consuming test. I don't think he could >>>>have afforded that kind of CPU time on a CRAY. >>>> >>>> >>> >>> >>>That is actually what I did. I used a Cray for about a year. Multi-cpu tests >>>could get about 5 minutes of "dedicated whole-machine" every hour followed by a >>>checkpoint and 55 minute wait for the next "slot". >>> >>>That's why I said it took way over a year to run all the tests to get the >>>results. Only exception was the 1 cpu tests which ran for long times, but with >>>1 cpu I could rely on CPU time rather than elapsed time. >> >> >>Even so, we still can't see the effect of pondering on the hash tables, since we >>are searching to a fixed depth. So the resemblance to real game conditions is >>still somewhat wanting. > >I agree. I fiddled with this during the CB testing. IE it should be possible >to mimic the effect by doing a ponder search for a fixed period of time, then >reading in the move and continuing. I did this. But on occasion the wrong move >gets played and the _rest_ of the test is ruined... I would have to re-read the >DTS article to remember exactly how I did this stuff since we are talking 10 >years ago. > > >> >>I have a tangential question. Assuming you have scads of memory, could you make >>a copy of the hash table(s) and ponder using the copy, then if the predicted >>move was not made, simply "context switch" to the before-ponder hash table? >>Would there be any benefit in that? Would such a copy operation not do for >>short time controls? >> >> > > >I've never had that much memory, even on a Cray. :) Is there any merit to the idea in principle? > > > > >> >> >>> >>> >>> >>> >>> >>>>> >>>>>>It is just a very hard question to answer. And change the positions and you can >>>>>>change the answer significantly... >>>>> >>>>>perhaps, perhaps not. you didn't measure it, and so you can't say :-) >>>>> >>>>>cheers >>>>> martin
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