Author: Robert Hyatt
Date: 20:11:47 09/21/01
Go up one level in this thread
On September 21, 2001 at 20:34:35, Vincent Diepeveen wrote: >On September 18, 2001 at 23:30:51, Dave Gomboc wrote: > >I already knew there are better move orderings possible because >i only get 0.85-0.90 cutoff rate versus most getting 0.90, however >static move ordering code is hell harder to write than simply >splitting in parallel and hoping it gives a quicker cutoff. > >The 0.92 from crafty is not entirely true , because we should not >forget that its fliprate is 0.05 versus mine is under 0.01 I don't follow that at all. If my 92% is higher than yours, then my "fliprate" must be lower... I don't see how it can be any other way. But in any case, my statistics on splitting at the wrong nodes suggests that I do very well there... > >So the qsearch can improve bigtime from crafty, because basically >that causes this bad fliprate! > >That all our move orderings can be improved was already known >and some years ago i posted bigtime about this subject but the same >Bob wrote here: > > "our move ordering is that optimal that we cannot improve it anymore". > I didn't say that. I said that our move ordering is producing the right move over 90% of the time, as I have carefully measured in my search statistics. 92% is a good average with 95% pretty common. That remaining 5% is not a huge problem. I certainly stand by the statement that if you can produce a > 2 speedup using 2 cpus, then you can copy that algorithm to a one processor machine and run faster than you have been running. Because your one-processor algorithm is bad. >completely contradicting with what is getting said now! > >>On September 18, 2001 at 18:27:01, Robert Hyatt wrote: > >>>Before you label a statement as ridiculous, find me _one_ person that will >>>side with you and say that "yes, it is possible to get a > 2 speedup using >>>only two cpus on anything but anomaly positions. Find _one_ person that will >>>agree... >> >>This is (okay, not very!) amusing... the statement is the exact opposite of >>reality, which (as Bob already knows) is that "it is only possible to get a < 2 >>speedup using only two cpus on anything but anomaly positions". >> >>If a parallel algorithm consistently outperformed a sequential algorithm, then >>you've just discovered a better sequential algorithm as well (use time-slicing). >> If you then don't use this better sequential algorithm to compare your parallel >>algorithm against, you'd be comparing a good parallel algorithm against a shitty >>sequential algorithm, which would make the speedup result worthless. >> >>It is absolutely key that when people compare their parallel algorithm to their >>sequential algorithm that they compare the best possible sequential algorithm. >>There are more than a few papers that don't do this... thankfully, at least some >>of them have been rejected. >> >>Dave
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