CUDALucas 2.04 self-tests pass, but testing fails

[johnp17321]

Hi,

I'm new to CUDALucas and trying it on my Ubuntu desktop with a GeForce GTX 550 Ti. It seems to work fine for small exponents but on larger, known Mersenne primes like M2976221, I get errors such as:

------- DEVICE 0 -------
name                GeForce GTX 550 Ti
totalGlobalMem      1073610752
sharedMemPerBlock   49152
regsPerBlock        32768
warpSize            32
memPitch            2147483647
maxThreadsPerBlock  1024
maxThreadsDim[3]    1024,1024,64
maxGridSize[3]      65535,65535,65535
totalConstMem       65536
Compatibility       2.1
clockRate (MHz)     1903
textureAlignment    512
deviceOverlap       1
multiProcessorCount 4

Continuing work from a partial result of M2976221 fft length = 160K iteration = 40037
Iteration = 40062 >= 1000 && err =   0.5 >= 0.35, fft length = 160K, writing checkpoint file (because -t is enabled) and exiting.

Anyone know what's up with that? Do I need to do some more testing/tuning or is my graphics card busted somehow?

-- John

[bcp19]

I've not worked much with cudalucas, but from what I've been reading, some of the 500 series cards seem to need a downclock to run error free.

[kladner]

The round off errors are like what I got with the VRAM running too fast (though within spec.)

If you are operating under Windows, you can use one of the several utilities out there like MSI Afterburner to adjust the memory clock. This core clock speed is likely not the issue.

[johnp17321]

Thanks bcp and kladner. This is a Linux-only box; are there any GPU downclocking tools available for *nix? Don't feel like buying (or, ahem... "buying") Windoze just to be able to downclock, but maybe I will if it's the only option.

[chalsall]

Originally Posted by johnp17321

Thanks bcp and kladner. This is a Linux-only box; are there any GPU downclocking tools available for *nix? Don't feel like buying (or, ahem... "buying") Windoze just to be able to downclock, but maybe I will if it's the only option.

Sadly, at the moment, running Winblows is the only option to down-clock Nvidia cards.

We Linux users tend not to game much (thus we tend to use GPUs for compute), so we're considered parasitic....

[kracker]

Originally Posted by chalsall

...
We Linux users tend not to game much (thus we tend to use GPUs for compute), so we're considered parasitic....

...because there are NO games for linux(at the moment) that requires more than a entry-low end gpu.

Sorry.

But seriously, Nvidia needs to pay more attention to linux... I hear AMD has overclock on linux, though. (AMDOverdriveCtrl)

[chalsall]

Originally Posted by kracker

...because there are NO games for linux(at the moment) that requires more than a entry-low end gpu.

IMHO, Linux users tend to be a little more serious. Those Linux users who play games would probably be less interested in Frames per Second (FpS) in some First Person Shooter (FPS), and more interested in how many moves ahead could be analyzed in Chess or Go et al.

Originally Posted by kracker

But seriously, Nvidia needs to pay more attention to linux... I hear AMD has overclock on linux, though. (AMDOverdriveCtrl)

Understand that Nvidia and AMD are also playing a game.

And we, their consumers, are their pawns....

[kracker]

Originally Posted by chalsall

Understand that Nvidia and AMD are also playing a game.

And we, their consumers, are their pawns....

Indeed. Right now in gaming, they are quite tied, although I don't know about TF performance between the two for $...

[chalsall]

Originally Posted by kracker

Indeed. Right now in gaming, they are quite tied, although I don't know about TF performance between the two for $...

You've hit the nail on the head. They're fighting between themselves about gaming.

Compute be damned.

As an aside, is there an OpenCL Lucas test yet?