Author: Dann Corbit
Date: 15:09:40 08/16/05
Go up one level in this thread
On August 16, 2005 at 17:46:10, Robert Hyatt wrote: >On August 16, 2005 at 17:37:30, Uri Blass wrote: > >>On August 16, 2005 at 17:30:02, Paolo Casaschi wrote: >> >>>On August 16, 2005 at 17:26:28, Dann Corbit wrote: >>> >>>>On August 16, 2005 at 17:16:33, Paolo Casaschi wrote: >>>> >>>>>>I know that usually when program improve they improve in all time controls. >>>>>>I do not know of evaluation changes or search changes that make programs weaker >>>>>>at blitz but stronger at long time control. >>>>>> >>>>>>In thoery it can happen but I need to see a proof for it and I believe that >>>>>>fabien mainly test in blitz time control(he can correct me if I am wrong) >>>>>>because usually productive changes in blitz of adding knowledge to the >>>>>>evaluation are also productive at long time control. >>>>> >>>>>Do you have any proof or evidence that there is some correlation between blitz >>>>>strenght and slower speed strenght? >>>>>If you dont, then we can only compare assumptions and I tend to agree with Bob >>>>>Hyatt since the same non-correlation is evident with humans and because common >>>>>sense... >>>> >>>>There is definitely a general correlation between strength at blitz and strength >>>>at standard time control. However, there are also exceptions to the rule. >>>> >>>>For instance, we will expect Fruit to be stronger than Golem at blitz, in the >>>>same way that we would expect Kasparov to clobber me at blitz. >>>> >>>>On the other hand, Mike Valvo overperforms at blitz, and Amy used to >>>>underperform badly (it was mostly due to bad algorithms for time management at >>>>fast time control). >>> >>>Exactly my point. >>>There is some correlation but there are exceptions and it's possible that >>>different players have a different type of correlation, thus the point of Bob >>>Hyatt stands. >>> >>>--Paolo >> >>I still need to see an example for programs without significant bugs that show >>significant difference(Amy is not a good example because of bad time management) >> >>There may be cases when A is 50 elo weaker at blitz and 50 elo better at long >>time control but I doubt if you can find cases when A is 100 elo weaker at blitz >>and 100 elo stronger at long time control. >> >>Uri > > >I'm not going to waste all day here, but a parallel search program can play >worse in endgames than in the middlegame, if sufficient care is not taken. >Would you really want to sic 8 cpus on a position which on average only has 4 >moves or less? Overhead goes thru the roof. It seems that 4 threads could work on the root node, and 4 threads on the next elements of the pv as one possibility. Probably a gross oversimplification, of course. >Same thing happens in blitz. Trees are a fraction of their normal size. To >split them invites excessive search overhead. In extreme cases (I have seen >this in Crafty) I get to do _zero_ splits in a blitz game (this happened in a >couple of the games Peter played today in fact) which means the search is >running about 1/6 its normal performance level. Think a factor of 6 slower will >make a measurable difference in speed vs normal chess? Easily. over-compensate >for that and you greatly slow the search down by having excessive split >overhead. And screwing up on this side of the equation can make the parallel >search _slower_ than a single-processor search, which can totally wreck >performance... > >Enough of this for the moment. The problem is real...
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