Author: Andrew Dados
Date: 16:55:50 03/27/01
Go up one level in this thread
On March 27, 2001 at 19:16:17, Uri Blass wrote: >On March 27, 2001 at 19:00:12, Andrew Dados wrote: > >>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- > >It is not clear. > >It also may be: >Before 35 wins and 30 draws. >After 35 wins and 37 draws. So first run would take 65 and second 72 games. I thought we were talking same number of games... > >In this case you win 0 games more than before and the 3.5 difference is only >because you lose less than before. > >Uri
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