GPU enabled functions react slow on first call
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Dear community, I want to utilize the GPU of my system to accelerate matrix multiplication. From the list of GPU-enabled functions, I can see that "mtimes" is available, therefore it should be accessible using gpuArrays.
My system is:
Matlab R2016b
Visual Studio 2013
CUDA 9.0
GTX 1070
I start by defining two matrices as gpuArrays:
>>gDexMat=gpuArray(DexMat);
>> gx_PD=gpuArray(x_PD);
>> whos gDexMat gx_PD
Name Size Bytes Class Attributes
gDexMat 200000x1000 4 gpuArray
gx_PD 1000x200000 4 gpuArray
I then perform the multiplication, gather the data and stop the time how long it took:
>> tic;gIQMat=gx_PD*gDexMat;IQMat=gather(gIQMat);toc %doing the demodulation
Elapsed time is 0.528126 seconds.
>> tic;gIQMat=gx_PD*gDexMat;IQMat=gather(gIQMat);toc
Elapsed time is 0.414626 seconds.
>> tic;gIQMat=gx_PD*gDexMat;IQMat=gather(gIQMat);toc
Elapsed time is 0.405255 seconds.
In this example, the time it took is pretty constant. However, when I start Matlab the first time, the execution may take extremely long, up to 45 seconds. Even the first call:
>>gDexMat=gpuArray(DexMat);
Can sometimes take up to a minute.
Does any body have any ideas why this is happening? Best, Ludwig
采纳的回答
Joss Knight
2017-10-27
1 个投票
MATLAB R2016b is built with CUDA 7.5. The first time you load the GPU libs they have to be just-in-time compiled to match your Pascal-architecture GPU. See the answer here for an explanation and some steps to prevent this compilation happening every time.
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