Author: Tony Werten
Date: 22:57:38 08/16/05
Go up one level in this thread
On August 16, 2005 at 18:17:16, Robert Hyatt wrote: >On August 16, 2005 at 18:09:40, Dann Corbit wrote: > >>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. > >Yes it is. I need to know the "alpha" value for the root before I sic 4 >processors to work there else overhead goes up (the young-brothers wait type >approach)... :) Actually, you don't :) If the alternative is no splits at all, one might just let the processors search with their own alpha beta window for each move. Tony > > >> >>>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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