Author: Andrew Dados
Date: 16:00:12 03/27/01
Go up one level in this thread
On March 27, 2001 at 18:12:42, Christophe Theron wrote: >On March 27, 2001 at 14:08:03, Robert Hyatt wrote: > >>On March 27, 2001 at 12:55:10, Christophe Theron wrote: >> >>> >>> >>>That's right. >>> >>>Actually as the title says, the message is directed to people who are >>>considering to buy a dual. >>> >>>As far as I know quads are so expensive that it would be ridiculous to buy one >>>just to play chess. >>> >>> >>> >> >> >> >>At the moment, perhaps. 6 years ago duals were just as expensive. Now they >>are dirt cheap. As quads become more common, their prices will continue to >>drop. 5 years ago a quad MB for pentium pro 200s would set you back almost >>$8,000. Today you can buy an Intel SC450NX for 2500 bucks, that includes >>three hot-swappable 400 wat power supplies, motherboard, 6-slot hot-swap raid >>disk cage, 3 on-board scsi controllers, 1 on-board video controller, etc. >> >>All you lack is cpus, memory and drives. >> >>That is a huge reduction. The curve is going downward each year. Now the >>quads are slowly reaching reasonable price points while the 8-way boxes are >>way expensive. In 5 years that too will change I'll bet... > > > >So I would advice people who are considering buying a dual right now to delay >their buy by several years... > > > > > >>>You are always thinking with unlimited resources in mind! >>> >>>I don't disagree with you here, but in real life there are people wondering if >>>it's worth it to buy a dual. >>> >>>And depending on how much money they can put on it, they will have to choose >>>between a single 1.GHz and a dual 1GHz. >> >>OK... but there the dual will perform like a 1.7ghz machine. Which will >>turn into around 60 rating points improvement. That is not trivially >>ignorable. >> >>Each time I teach a parallel programming course here, I will find around one >>out of every 10 students has a dual-processor machine already. And when I ask >>what they paid, they generally say 500-1000 US bucks... > > > >In the place I live, I cannot even buy a dual. I must order it overseas. > >Bob, there are people outside the United State of America, you know. > >You are very lucky to live in a place where you can get all kind of high tech >stuffs for a fraction of your monthly salary, but in other countries a dual >represents a huge amount of money. > >For example, a dual represents more than my average monthly salary. > > > > > >>>If you can afford to buy a dual 1.2GHz, then you just stop after reading the >>>first paragraph. >>> >>>If not, then I think the rest is worth reading... >>> >>> >>> >>> >>>>That is flawed. For multiple reasons. The shared hash table holds _most_ EGTB >>>>results after a single probe. The EGTB cache is threaded and shares data read >>>>between the two (or more threads). With the compression scheme Eugene uses, >>>>the reads are kept to a minimum. I have run extensive tests on my quad with >>>>one single 9-gig SCSI drive servicing 4 threads for EGTB reads. I don't see >>>>any severe strangulation due to disk backlogs. most threads are searching >>>>close enough to each other in the tree that they are probing the _same_ >>>>tablebases. The caching Eugene wrote handles this quite well. >>> >>> >>> >>>OK, I admit that I have not done any test on this issue, so your input is >>>appreciated. >>> >>>If my figures are wrong I will publish an update for this text. >>> >>>Do you have any measure of the slowdown expected when 2 thread are accesing >>>intensively the same EGTB files? That would help us to compute the corresponding >>>ELO loss. >> >>I generally don't notice any degradation at all. Mainly because of the large >>well-managed cache buffers, no doubt. But then the operating system also does >>a lot of file caching on top of what Eugene does, and all of this (on a 512mb >>machine) goes a long way toward controlling "disk buzz". > > > >Well on my computer when I set up an endgame position I have my hard disk >working really hard. > >I can hardly see how this poor hard disk could manage to serve two threads >instead of one without some performance penalty. > >On the other hand, if you need to have a high perf SCSI drive to satisfy the >needs of the dual, and such an amount of memory, this has to be added to the >invoice. > >Remember that all this is about what you get for the money, what you need really >and is it worth it. > > > > > >>>I did not try to cover quads in the message because I don't think many people >>>could afford to buy one. >>> >> >>I realize that. But 5 years ago you wouldn't have found anyond considering >>buying a dual either. Quads will eventually reach the same pricing level, >>based on a curve over the last 5 years.. > > > >People, wait for 5 years before you buy a SMP machine. > > > > > >>>So far I have seen a number of people on CCC asking for duals, but nobody ever >>>said he was considering to buy a quad. >>> >>> >>> >>> >>> >>>>>A difference in ELO points in real life turns into a winning percentage. >>>>>That's exactly what ELO means, and how it is computed. >>>>> >>>>>For winning percentages above 20% and under 80%, there is an approximated >>>>>formula that works pretty well: >>>>> >>>>> ELOdiff = ( WinPercentage - 50 ) * 7 >>>>> >>>>>From this you can deduce how to compute WinPercentage if you have the ELOdiff: >>>>> >>>>> WinPercentage = ELOdiff / 7 + 50 >>>>> >>>>>If ELOdiff=25, then WinPercentage = 53.57% (we are between 20% and 80% >>>>>so our above formula applies). >>>>> >>>>>So we are talking about a difference of 3.5 games each time you play 100. >>>>> >>>>> >>>>>**************************************************************************** >>>>>** When you play 100 games with your dual 1GHz against ** >>>>>** your single 1.2GHz, you can expect the dual to win typically ** >>>>>** by a 3.5 games margin. ** >>>>>**************************************************************************** >>>> >>>> >>>>I would change that to >>>> >>>>winpct=60/7+50 which is about 60%. Out of 100 games that turns into winning >>>>60 and losing 40. BTW in your above comment you need to double that 3.5. If >>>>I win 53.5 games out of 100, you win 46.5. The _difference_ is 7 games. Not >>>>3.5 >>> >>> >>>When you win a game, your opponent loses it. I don't count this as 2 games. >>> >>> >>> >>> >> >>Then maybe your term wasn't clear to me instead. You said "I win 53.5% of >>the games. Out of 100 games that is a difference of 3.5 games." If I win >>53.5% of the games, you win 46.5% of the games. That is a bit different >>since our scores are separated by 7, not 3.5... > > > >OK, OK. I don't want to split hairs. > >What counts is the difference between the winning percentage and 50%. Because it >is what you multiply by 7 to get an estimate of the ELO difference. > >If I run a match with even hardware, I win 50 out of 100 games. > >If I run a match with a dual I win 53.5 out of 100 games. > >With my dual I win 3.5 more games. OK? NO, you win 7 games more then before :) before: 100 draws; now: 93 draws and 7 wins... -Andrew- > > > > Christophe
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