Author: Uri Blass
Date: 20:02:16 03/27/01
Go up one level in this thread
On March 27, 2001 at 19:55:50, Andrew Dados wrote: >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... Both tests are 100 games. I counted only wins and draws. The rest of the games are losses(35 in the first case and 28 in the second case) Uri
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