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CULA • View topic - CULA is not using my GPU!?

CULA is not using my GPU!?

General discussion for CULA. Use this forum for questions, examples, feedback, and feature requests.

CULA is not using my GPU!?

Postby omidkar » Tue Apr 23, 2013 4:30 pm

Hi,

I am new to using CULA. I have a code in which a sparse linear system of equations is to be solved
using preconditioned conjugate gradient methods provided in CULA Sparse.
I have tried all solver&preconditioner combinations, but all of them appear to be much slower than the same code on CPU. Then I am thought perhaps CULA does not actually use my GPU. Using GPU-Z software, I monitored the performance of the GPU while the CULA code was running. It turned out that the Tesla K20 was not really used at all during the code running. Some of the details of my work is as follows:

I have two GPUs on my system, Tesla K20 and Quadro 600. But the one I'd like to use for my codes is Tesla K20. As you know, it is the latest available GPU from Nvidia, and is supposed to work superbly faster.
Also, I am using PGI Visual Fortran, which uses CUDA fortran architecture.
Finally, when running the code, after CULA initialization, I get the following warining:
"your GPU <Tesla K20c> does not have full double-precision perf. As such, you may not be able to use CULA Sparse to its full potential. Recommended cards include the Tesla 20 series and Quadro 6000".

Could somebody please help me with this issue?

Many thanks,

Omid
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Re: CULA is not using my GPU!?

Postby john » Wed Apr 24, 2013 5:53 am

You can ignore that warning - it is spurious and will be removed in the next version. NVIDIA doesn't provide a reliable way to detect full double precision, and the K20C has been misdetected by our warning code.

Your GPU will definitely be used for this computation. Performance will depend on which GPU was selected (there is a chance that your Quadro has been selected) and the matrix itself. You'll want to make sure the K20 is selected, by either using cudaSetDevice or the CUDA_VISIBLE_DEVICES environment variable. But even if the GPU is selected, it's possible that under certain circumstances the GPU could still be slower than the CPU - for instance if your matrix is very small, or if you converge in just a few iterations. It's all very problem dependent from here.
john
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Re: CULA is not using my GPU!?

Postby chongteng » Sat Sep 27, 2014 8:53 am

chongteng
 
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Joined: Mon May 05, 2014 7:34 am


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