GPU wrong results
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Hello, I just started using GPU with matlab and I get some strange results. I run the following code
a = rand(2^10,2^10,'single');
G = gpuArray(a);
F = fft2(G);
err = isequal(gather(G), a)
Normally the value o 'err' should be 1, but in this case is not. If you call another function, e.g. instead of fft2 call atan, then the value of err is 1. Do you have any idea why this happens?
The GPU model is "GeForce GTX 580" and the matlab version is 2010b.
Thanks a lot.
7 Kommentare
Walter Roberson
am 31 Okt. 2011
It appears that the German Wischi-Waschi came down to English as "wishy-washy". I had no idea of the origin of the English term before.
Antworten (2)
Jan
am 27 Okt. 2011
Do you expect absolutely equal results without rounding errors? This will happen as an exception only. Please check:
g = gather(G);
disp(max(abs(g(:) - a(:))));
4 Kommentare
Jan
am 31 Okt. 2011
A large FFT2 produces some heat on the GPU. Does this influence the local memory such that your data are simply corrupted?
Thomas
am 2 Nov. 2011
Georgios, I ran it on our GPU pool
gpuDevice
tic ()
a = rand(2^10,2^10,'single');
G = gpuArray(a);
F = fft2(G);
err = isequal(gather(G), a)
toc ();
The output was ans =
parallel.gpu.CUDADevice handle
Package: parallel.gpu
Properties:
Name: 'Tesla M2070-Q'
Index: 1
ComputeCapability: '2.0'
SupportsDouble: 1
DriverVersion: 4.1000
MaxThreadsPerBlock: 1024
MaxShmemPerBlock: 49152
MaxThreadBlockSize: [1024 1024 64]
MaxGridSize: [65535 65535]
SIMDWidth: 32
TotalMemory: 5.6366e+09
FreeMemory: 5.5281e+09
MultiprocessorCount: 14
ClockRateKHz: 1147000
ComputeMode: 'Default'
GPUOverlapsTransfers: 1
KernelExecutionTimeout: 0
CanMapHostMemory: 1
DeviceSupported: 1
DeviceSelected: 1
err =
1
Elapsed time is 0.054194 seconds.
I am getting an err = 1 output..
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