Author: Dave Gomboc
Date: 09:42:54 09/22/01
Go up one level in this thread
On September 22, 2001 at 12:06:36, Uri Blass wrote: >On September 22, 2001 at 10:05:58, Robert Hyatt wrote: > >>On September 22, 2001 at 00:48:21, Uri Blass wrote: >> >>> >>>I do not express an opinion about the possible speed improvement that you can >>>get from parallel search today but >>>I do not see that the rest is already there. >>> >>>1)The fact that you need 2 minutes to implement R=3 in Cray blitz means nothing >>>if you did not test R=3 when you tested the speed improvement from parallel >>>search. >> >> >>I don't know what you mean here. In the Cray Blitz papers, I used R=1. That >>was what I used in the normal program. I have also reported here (many times) >>on the speedup for Crafty. Which is right in line with Cray Blitz. >> >>Null move has _nothing_ to do with parallel search efficiency. I have data >>from Cray Blitz with _no_ null-move. With R=1. And with Crafty with >>R=2 and R=2~3. There is no difference in the performance that I can find. >> >>So this entire discussion leaves me wondering just exactly what he is talking >>about. >> >> >> >>> >>>2)Vincent is right that the machine is hell slower than nowadays single cpus >>>because he talks about Cray blitz from 15 years ago and not about the latest >>>cray blitz that can search 7M nodes per second. >> >>15 years ago would be the YMP. That is not "hell slow". The machine had >>8 cpus at roughly 200mhz although that is not the way to measure the speed of >>a machine that can produce multiple arithmetic results in one clock cycle. >> >>I'd take that old YMP, circa 1986, over _any_ PC today for pure >>number-crunching. >> >> >> >> >>> >>>I understand that his claim is about long time control and the only way to test >>>if he is right is to take a lot of positions from games when the machine changes >>>it's mind after a long search and to compare the time that it needs >>>to do it without parallel search and the time that it needs to do it with >>>parallel search when the hash tables are the same. >> >> >>His claim is simply nonsense. I have explained why already. If he can produce >>a speedup of > 2 with 2 processors, then using two processes on a single-cpu >>machine will produce a speedup > 1. The proof is trivial. And the concept >>is ridiculous. >> >> >> >> >> >>> >>>I have positions when Deep Fritz changed it's mind after a long search from my >>>correspondence games but I have not multi processor. >>>If people are interested in testing it I may send them my positions >>>and they may use them in order to test the speed improvement of Deep Fritz from >>>parallel search. >>> >>>I agree that speed improvement of more than being 2 times faster from 2 >>>processors means that it is possible to improve the program when it is using 1 >>>proccesor. >>> >>>Uri >> >> >>Which means the test is simply invalid. The sequential search has to be fixed >>first. > >It means that the test is an important test because if the 2 processors are more >than twice faster than one processor for some programs then it is clear that >there is a room for improvement in the sequential search in the future(it is >possible that there is a room for improvement at long time control but the >programmers simply did not care for that because they care only about tournament >time control). > >It is also important for buyers to know it because if Deep Fritz with 2 >processors is more than twice faster than Deep Fritz with one processor at long >time control(I do not claim that it is the case) then it means that 2 processors >can be more important for correspondence games. > >Uri It isn't that there is room for improvement in the sequential search "in the future", it's that there is room for improvement in the sequential search _immediately_. Now, if that improvement isn't made, then you're testing a good parallel implementation against a poor sequential implementation, so your speedup value is meaningless. Dave
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