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Reduce cuFFT memory usage by re-using the memory space between the forward and backward FFT operations #3

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Reduce cuFFT memory usage by re-using the memory space between the forward and backward FFT operations #3

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22 changes: 22 additions & 0 deletions cdmt.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,7 @@ int main(int argc,char *argv[])
unsigned char *cbuf,*dcbuf;
float *fbuf,*dfbuf;
float *bs1,*bs2,*zavg,*zstd;
void* cufftworkarea;
cufftComplex *cp1,*cp2,*dc,*cp1p,*cp2p;
cufftHandle ftc2cf,ftc2cb;
int idist,odist,iembed,oembed,istride,ostride;
Expand Down Expand Up @@ -188,13 +189,33 @@ int main(int argc,char *argv[])
checkCudaErrors(cudaMalloc((void **) &ddm,sizeof(float)*ndm));
checkCudaErrors(cudaMemcpy(ddm,dm,sizeof(float)*ndm,cudaMemcpyHostToDevice));


// Disable initial memory allocates and silence the compiler warnings;
// Nvidia uses a custom compiler frontend so GCC pragmas do not work.
// This order-of-execution follows Nvidia's usage guidance
#pragma diag_suppress used_before_set
cufftSetAutoAllocation(ftc2cf, 0);
cufftSetAutoAllocation(ftc2cb, 0);
#pragma diag_default used_before_set
size_t cfSize, cbSize;

// Generate FFT plan (batch in-place forward FFT)
idist=nbin; odist=nbin; iembed=nbin; oembed=nbin; istride=1; ostride=1;
checkCudaErrors(cufftPlanMany(&ftc2cf,1,&nbin,&iembed,istride,idist,&oembed,ostride,odist,CUFFT_C2C,nfft*nsub));
checkCudaErrors(cufftGetSizeMany(ftc2cf,1,&nbin,&iembed,istride,idist,&oembed,ostride,odist,CUFFT_C2C,nfft*nsub, &cfSize));

// Generate FFT plan (batch in-place backward FFT)
idist=mbin; odist=mbin; iembed=mbin; oembed=mbin; istride=1; ostride=1;
checkCudaErrors(cufftPlanMany(&ftc2cb,1,&mbin,&iembed,istride,idist,&oembed,ostride,odist,CUFFT_C2C,nchan*nfft*nsub));
checkCudaErrors(cufftGetSizeMany(ftc2cb,1,&mbin,&iembed,istride,idist,&oembed,ostride,odist,CUFFT_C2C,nchan*nfft*nsub,&cbSize));


// Allocate the maxmimum memory needed
size_t minfftsize = cfSize > cbSize ? cfSize : cbSize;
checkCudaErrors(cudaMalloc((void**) &cufftworkarea, (size_t) minfftsize));
// Set the cuFFT handles to use this area
cufftSetWorkArea(ftc2cf, cufftworkarea);
cufftSetWorkArea(ftc2cb, cufftworkarea);

// Compute chirp
blocksize.x=32; blocksize.y=32; blocksize.z=1;
Expand Down Expand Up @@ -343,6 +364,7 @@ int main(int argc,char *argv[])
// Free plan
cufftDestroy(ftc2cf);
cufftDestroy(ftc2cb);
cudaFree(cufftworkarea);

return 0;
}
Expand Down