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2013-03-14, 02:57   #221
LaurV
Romulan Interpreter

Jun 2011
Thailand

863510 Posts

Quote:
 Originally Posted by ewmayer Based on all the tests done to date, what is the error rate?
Unknown. Some people do "in house" double checks before reporting CL results, and "spidering" won't help. I have about 10% error rate for the tests I do. I never counted exactly, but I still remember Feb-March 2012, when CuLu changed to non-power-of-2 FFT and the intermediary versions used to give wrong residues, after that date I always run two copies of CuLu in two different cards, and maybe with two different FFT sizes, and report the result only if I have a match. This is still faster than using P95 in the loop, and anyhow it will need a third party to do the DC. So, the results reported to the server are not relevant. Also, if someone only do DCLL, they won't report mismatching results, and they will TC first.

For me, running in parallel allows me to catch the error in the earliest phase, and save the time which would be wasted if the test is allowed to finish. When I have two non matching residues, I re-do both from the last saving.

From my experience, with overclocking (water cooled) the errors are around 10%, maybe more. Without overclocking the value is much lower, maybe 2% or so, but I am still not confident enough to giveup "in-house double checking".

The 10% can look a lot, but you have to think about the fact that if you test 10 exponents of 50M, then you do 500M iterations, and if only one iteration in those 500M is wrong, you got one of your 10 expos wrong, so here is your 10%.

There is no mystery into it. For me the real mystery is how P95 (and the CPUs in general) can do 500 MILLIONS iterations, without getting any of them wrong....

 2013-03-14, 08:15 #222 ET_ Banned     "Luigi" Aug 2002 Team Italia 11·433 Posts I am running DC and LL on my cards. Since I started, I only had 3 non-matching results, two of them were subsequently found correct. Luigi
2013-03-14, 10:24   #223
ATH
Einyen

Dec 2003
Denmark

B4B16 Posts

Quote:
 Originally Posted by nucleon Another Titan double check match. Processing result: M( 29325073 )C, 0x23c2d7bc0d08e8d4, n = 1835008, CUDALucas v2.03 LL test successfully completes double-check of M29325073 CPU credit is 29.1622 GHz-days. To me looks like underclocking the RAM did the trick. The hard part now is to work out the most efficient use of this card. -- Craig
What options do you have for RAM clocking? Max is 6.008 Ghz? (According to the review articles):
Quote:
 Memory Clock 6.008GHz GDDR5
2500 Mhz now seems stable, have you tested the stability of anything between those?

Last fiddled with by ATH on 2013-03-14 at 10:25

2013-03-14, 11:43   #224
nucleon

Mar 2003
Melbourne

10038 Posts

Quote:
 Originally Posted by ATH What options do you have for RAM clocking? Max is 6.008 Ghz? (According to the review articles): 2500 Mhz now seems stable, have you tested the stability of anything between those?
It seems I can adjust in roughly 1MHz increments. The 2500 figure is based on a starting figure of 3000MHz. I guess the app I used measures the clock waveform, and the 6000MHz figure is the sexed-up DDR figure.

The reduction in performance was about 10+% ish. Given it takes a long time to verify stability, as LL double checks seem to be the only reliable way to verify. I'm too lazy to fiddle to optimize ram speed. (It's going to take a while :) )

-- Craig

 2013-03-14, 16:05 #225 Redarm     Apr 2012 Berlin Germany 3·17 Posts 2900 mhz produces errors (3.1ms per I M48) 2750mhz seems stable for now (3,35ms per I M48)
2013-03-14, 16:42   #226
frmky

Jul 2003
So Cal

23×11×23 Posts

Quote:
 Originally Posted by ewmayer Based on all the tests done to date, what is the error rate?
I'm using older cards that are not over clocked, but in what must now be well over 100 tests, I've had one known bad result. That's under a 1% error rate.

2013-03-14, 16:47   #227
ATH
Einyen

Dec 2003
Denmark

72×59 Posts

Quote:
 Originally Posted by Redarm 2900 mhz produces errors (3.1ms per I M48) 2750mhz seems stable for now (3,35ms per I M48)
Ok, so 2500mhz is pretty close to the unstable crossover. Wierd that these benchmark programs showed no errors.

Quote:
 Originally Posted by nucleon Doing further testing... Furmark - no issues MemtestG80 - no issues occt - no issues

 2013-03-14, 17:52 #228 Redarm     Apr 2012 Berlin Germany 3×17 Posts found a way to find errors produced by vram instructions coming soon ... (memtestg80 is essential)
2013-03-14, 19:32   #229
Brain

Dec 2009
Peine, Germany

33110 Posts
100M

Quote:
 Originally Posted by Redarm 2000h
2500MHz VRAM = 2070h:
Code:
E:\Eigene Dateien\Computing\CUDALucas\2.03\D0>CUDALucas-2.03-5.0-sm_35-x64.exe -threads 512 -f 20971520 -t 332192831
Warning: No ini file detected. Using defaults for non-specified options.
Starting M332192831 fft length = 20971520
Iteration 10000 M( 332192831 )C, 0x7e591d0cbd938d73, n = 20971520, CUDALucas v2.03 err = 0.0332 (3:44 real, 22.4112 ms/iter, ETA 2067:55:55)
Iteration 20000 M( 332192831 )C, 0xc2eda19e28f00bf4, n = 20971520, CUDALucas v2.03 err = 0.0339 (3:44 real, 22.4587 ms/iter, ETA 2072:14:52)
Iteration 30000 M( 332192831 )C, 0x4e96b2da36fcce56, n = 20971520, CUDALucas v2.03 err = 0.0352 (3:44 real, 22.4425 ms/iter, ETA 2070:41:49)
No guarantee for the residues... ;-)

2013-03-14, 19:38   #230
chalsall
If I May

"Chris Halsall"
Sep 2002

32×1,019 Posts

Quote:
 Originally Posted by Brain 2500MHz VRAM = 2070h
Less than three months...

Nope. Still doesn't Make Sense(tm)....

2013-03-14, 21:02   #231
kracker
ἀβουλία

"Mr. Meeseeks"
Jan 2012
California, USA

1000011011112 Posts

Quote:
 Originally Posted by chalsall Less than three months... Nope. Still doesn't Make Sense(tm)....
In one way it still makes sense to do them on CPU... I mean, 22 ms for a 30M exp.?? On a \$1000 card?

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