Author: Robert Hyatt
Date: 09:21:31 05/05/04
Go up one level in this thread
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. :) > > >> >> >> >> >> >>>> >>>>>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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