Compiling FFTW with MPI in C

Question

I have installed both Open MPI and FFTW onto my mac. I've successfully used FFTW, now I'm trying to use it with MPI.

Here is what I am trying to run:

int main(int argc, char **argv){ clock_t time0, time1; int N = 10; fftw_complex *in, *out; fftw_plan p; MPI_Init(&argc, &argv); fftw_mpi_init(); in = (fftw_complex*) fftw_malloc(sizeof(fftw_complex) * N); out = (fftw_complex*) fftw_malloc(sizeof(fftw_complex) * N); p = fftw_mpi_plan_dft_1d(N, in, out,MPI_COMM_WORLD, FFTW_FORWARD, FFTW_ESTIMATE); for (int i = 0; i<N; i++) { in[i]=i+(i+1)*I; } time0 = clock(); fftw_execute(p); time1 = clock(); printf(" FFT time = %f \n\n", (float)(time1 - time0)/CLOCKS_PER_SEC); fftw_destroy_plan(p); fftw_free(in); fftw_free(out); MPI_Finalize(); return 0; }

Here is how I am attempting to compile:

gcc -I/usr/local/include test.c -L/usr/local/lib -lfftw3_mpi

This is nearly identical to how I compiled without mpi and all worked fine:

gcc -I/usr/local/include test.c -L/usr/local/lib -lfftw3

But Now I see a lot of this:

How can I fix this issue? I know I installed OpenMPI, the installation of FFTW failed without it.

I did that and still had the same issue but with different functions so I also added -lfftw3 and now it works, thank you!! — Burgundy
– Burgundy, Commented Sep 14, 2016 at 19:41
Actually it looks like OpenMPI isn't that straightforward -- try mpicc -I/usr/local/include test.c -L/usr/local/lib -lfftw3_mpi — Dmitri
– Dmitri, Commented Sep 14, 2016 at 20:25
it compiled both ways, both saw the same time computing the fft — Burgundy
– Burgundy, Commented Sep 14, 2016 at 21:36

petrmikheev · Accepted Answer · 2016-09-15 16:03:07Z

1

Add -lfftw3 after -lfftw3_mpi
Use mpicxx instead of gcc

Command: mpicxx test.c -lfftw3_mpi -lfftw3

answered Sep 15, 2016 at 16:03

petrmikheev

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