I don't like this conclusion, I would prefer to figure out how to refine the fft selection process. The only reason I can see to avoid the lengths that are not multiples of 16K, 32K, etc. is that one block in the second nomalize kernel will have some idle threads. For example, using 1701k fft and threads = 512, one out of 27 blocks in normalize2_kernel has about 42% idle threads. But this is only 42% of 1/27 of ~1/7 of ~1/4 of the total iteration time. Hardly noticible. To test this I ran a few iterations with fft = 1701k and the iteration times matched well with the prediction from the cufftbench test, 3.238 actual as opposed to 3.234 predicted. (I use 2 * cb + a * fft, a = .00044 for my 570.)

Thanks for pointing me back to previous posts in this thread. I thought I had read the entire thing several times over, but looking for msft's posts about fft length, I found whole sections I must have slept through. In particular there are many posts which have cufftbench data I had never seen before.

I hope this is the correct thread for my questions:

This week I downloaded CL to see what my GTX570 could do.
The self test ("-r") ran twice without problems (apart of annoying sound from the gfx card, varying with different FFT lengths).

Then I decided to do some "real" LL-ing and put a M59.xxx.xxx exponent in worktodo.txt.
CL ran for a while (CL choose FFT length 3670016) and then stopped due to rounding error. After starting CL again it went on a while, but then stopped again (again err >= 0.35). That happened several times, so I wonder if the result has even a chance of being correct because of the huge(?) number of rounding errors (>10 until now).

Then I tried M26026433 to compare the residues with the residues frmky kindly published. At 350101 iterations I got a rounding error (and CL exited), but the residues matchted up to 350000 iterations. After starting CL once more the residues still matched, but 30000 iterations later the next rounding error appeared.
So should I continue on the M59.xxx.xxx exponent (about 1/2 of the work is done), or is it just a waste of time, since the result is probably not correct?

The other thing I don't know is why the rounding errors appear and disappear despite using the same FFT length. Does it mean the gfx card is faulty? CPU temperatur was up to 69C, CPU about 71C (probably because of Mprime95). I use the precompiled CUDALucas-2.03_cuda4.0_sm_20-x86-64.exe, Windows7 64bit, and a GigaByte GV-N570OC-13I.

Any comments are welcome.

Current changes are being made to address your issues and others, as well. v2.05 should be ready for testing soon. We'll post when the version is up for testing.

Jerry

[QUOTE=flashjh;330929]Current changes are being made to address your issues and others, as well. v2.05 should be ready for testing soon. We'll post when the version is up for testing.

Jerry[/QUOTE]
Current changes are being made to address "increasing the FFT size on the fly" when the default one is too small and this is found later in the test, to avoid re-starting everything from the beginning.

However, this is not his problem, as the errors are NOT reproducible. His problem is thermal.

@Keldor: Please run some temperature monitoring software (GPU-Z from PowerTech is a good start) and monitor the temperature of your card. When it gets very hot, it may spit random things, which CL will treat like errors. The "noises from the card" is an indicative of the fact that the fans are running like crazy. You may have to clean the dust, and ensure a proper ventilation around your computer case. Under a closed desk or in a very warm ambient, it will not feel so comfortable.

Edit: and do DC for a while, expos around 30M-35M, until you are sure the card is running well and stable. Only after that you can go to first-time-LL. Otherwise you will feel very sorry 2 years later when I will find a prime during DC for an exponent you did LL and got bad residue... :razz:

Thank you for the information.
The GPU temperatur stayed always < 70C, which shouldn't be a problem since fan speed is about 50% (sorry for the typing error in my first post, the first "CPU" should be "GPU").
The "noises from the card" are not from the fans. I can reproduce them with the self-test or by going to the loading screen of some games. (Sounds like in this video [URL]http://www.youtube.com/watch?v=CzHwXuujpZo[/URL] but it's not a CL problem.)

So I will complete the current exponent (3/4 done) and switch to DC (or TF) afterwards.

[URL="http://www.youtube.com/watch?v=CzHwXuujpZo"][/URL]

In that case you must have just gotten unlucky and been assigned an exponent that's right near an FFT crossover point.

2.05 will have code to deal with these issues without straight up aborting.

[QUOTE=Keldor;330794]... and a GigaByte GV-N570OC-13I.

Any comments are welcome.[/QUOTE]
I am afraid I have bad news for you.

Welcome to the club -- in two senses: 1) to the mersenneforum, and 2) the club of unlucky GV-N570OC-13I owners.

I am not alone here who already swapped this particular card multiple times (there's at least one more owner who was likewise lured by the attractive design). I returned one of them (without charge) when it failed many cuda tests (genefer, cudalucas, some others). With the second specimen, I am stuck for half a year, during which I already had two RMAs, and now in the process of the third RMA. It fails every 1.5-2 months (blows some transistors-or-capacitors* with nasty smell). This time I picked up the phone and complained, and got a verbal assurance that I am not going to receive the same card again (with a few replaced VRM elements) and I got a prepaid label this time. We’ll see what will be different this time. /sigh/

In comparison, my other card (EVGA 560-448 OC, twin-fan variant) works without any problems for a year.


____________
[SIZE=1]*I cannot tell precisely because these are under the sink and I am not curious enough to open and mess with the paste later to put it together again.[/SIZE]

The sound bit is also a true and annoying feature. I second that.
("It is a sound card!" :w00t:)

In my case, it is not that much annoying - maybe you have a worse specimen. In my hands, it was apparent for some very short job units, e.g. cudalucas -st2, or for many tests that I ran while debugging mmff-gfn on small ranges. For normal jobs, the card is silent.

[QUOTE=Batalov;330976]The sound bit is also a true and annoying feature. I second that.
("It is a sound card!" :w00t:)

In my case, it is not that much annoying - maybe you have a worse specimen. In my hands, it was apparent for some very short job units, e.g. cudalucas -st2, or for many tests that I ran while debugging mmff-gfn on small ranges. For normal jobs, the card is silent.[/QUOTE]

With three fans, yeah! My single fan GPU gets loud with the fan over ~55%
Under that, quiet.

Three fans are in fact silent[I][B]er[/B][/I] than one.

It is not the fans. It is probably not the GPU either, but some of the external circuitry; the VRMs, maybe. If they do vibrate under changing load characteristics (from idle to load, and again, and so on four thousand times under cudalucas -st2), hence the sound (it is similar to the 8-bit Mario brothers or Leisure Suit Larry type el cheapo music from the 80s) and hence the eventual blowups. That's just my guess.

If you have seen the Matrix, the sound is reminiscent of the sound that you can hear when Neo all covers with liguid metal and the POV camera flies into his mouth. :davieddy:

[QUOTE=LaurV;330930]Current changes are being made to address "increasing the FFT size on the fly" when the default one is too small and this is found later in the test, to avoid re-starting everything from the beginning. [/QUOTE]

Does the code already use an FFT-length-independent savefile format? That makes such length-changing hacks much simpler to effect.