Reduce cuFFT memory usage by re-using the memory space between the forward and backward FFT operations#3
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This is achieved by sharing the memory space between the cuFFT operations (since they cannot be executed in parallel), and only allocated the memory needed by the largest operation (though in this case they -should- be the same References https://docs.nvidia.com/cuda/cufft/index.html\#function-cufftgetsizemany https://docs.nvidia.com/cuda/cufft/index.html\#function-cufftsetautoallocation + further functions in 3.7
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Hey Cees,
Not the patch I was intending to upstream next, but I've been having endless issues with OpenMP forcing itself to be serial, so here's a quick win I came across.
cuFFT allows you to manage your memory usage yourself, so here we can only allocate the larger memory block needed for the cuFFT operation rather than allocating two separate blocks for each FFT. This saves me around 2GB in VRAM in my normal configuration, and I ran a test to compare it to what you've mentioned in the past (20 subbands I believe?) and it should be ~1GB saved in your case, so you could increase nforward or sample even more DMs
Cheers,
David