Concurrent write to gpuArray
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Is there a way for multiple threads of an arrayfun or other structure to write to the same gpuArray matrix, if I do not care about the order of writes (it is a array of falses and i only ever write trues) and will not read the array by gather until all threads are finished? Doing this by local output and reduction will consume too much memory.
Application: a monochrome 2d rasterizer that processes multiple polygons onto the frame buffer simultaneously
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Answers (2)
Matt J
on 8 Aug 2015
Edited: Matt J
on 8 Aug 2015
Even if there's a way, I think it will be very slow. GPUs are not designed to share large data across threads. However, one strategy might be to use gpuArray.arrayfun to prepare a table of the values to be written and their matrix coordinates (I,J,S). Then later, on the CPU, do
A_new=A_old+sparse(I,J,S)
Or, use accumarray instead of sparse(), if the resulting matrix is not sparse. Each GPU thread could compute a single triplet I(k),J(k), S(k) effectively assuming these computations are small, parallel, and don't share large data
Joss Knight
on 2 Sep 2015
In short, no, not in MATLAB code. arrayfun has to write one value per thread to a separate output address. Write a CUDAKernel or MEX function in C++.
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