I ran into a similar issue: http://stackoverflow.com/questions/13187443/nvidia-cufft-limit-on-sizes-and-batches-for-fft-with-scikits-cuda
The long and short of it is that CUFFT seems to have a limit of approximately 2^27 elements that it can operate on, in any combination of dimensions. In the StackOverflow post above, I was trying to make a plan for large batches of the same 1D FFTs and hit this limitation. You'll also notice that the benchmarks on the CUFFT site https://developer.nvidia.com/cuFFT go up to sizes of 2^25. I hypothesize that this is related to the 2^27 "Maximum width for a 1D texture reference bound to linear memory" limit that we see in Table 12 of the CUDA C Programming Guide http://docs.nvidia.com/cuda/cuda-c-programming-guide/#compute-capabilities. So since 4096**2 is 2^24, increasing to 8096 by 8096 gets very close to the limit, even though you'd think 2D FFTs would not be governed by the same limits as 1D FFT batches. You should be able to achieve 8096 by 8096 and larger 2D FFTs by performing two separate sequentual 1D FFTs, one horizontal and the other vertical. The runtimes should nominally be the same (they are for CPU FFTs), and the answer will be the same, up to machine precision. On Thu, Dec 5, 2013 at 9:53 AM, Jayanth Channagiri <[email protected]>wrote: > Hello > > I have a NVIDIA 2000 GPU. It has 192 CUDA cores and 1 Gb memory. > GB GDDR5 > > I am trying to calculate fft by GPU using pyfft. > I am able to calculate the fft only upto the array with maximum of 4096 x > 4096. > > But as soon after I increase the array size, it gives an error message > saying: > pycuda._driver.MemoryError: cuMemAlloc failed: out of memory > > Can anyone please tell me if this error means that my GPU is not > sufficient to calculate this array? Or is it my computer's memory? Or a > programming error? What is the maximum array size you can achieve with GPU? > Is there any information of how else can I calculate the huge arrays? > > Thank you very much in advance for the help and sorry if it is too > preliminary question. > > Jayanth > > > > > > _______________________________________________ > PyCUDA mailing list > [email protected] > http://lists.tiker.net/listinfo/pycuda > >
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