FFTW

From Vd

FFTW is installed at /site. There are two versions 2 and 3 installed for both AMD and Intel.

• fftw2/
• fftw2.intel/
• fftw3/
• fftw3.intel/

The libraries can be found at /site/fftw<version>/lib/libfftw3.a for the serial version and libfftw3_threads.a for the multi threaded version. Include files are found at /site/fftw<version>/include/ both for fortran (fftw3.f) and C (fftw3.h).

The number of threads are automatically detected from information about the node. The OMP_NUM_THREADS are not read by the FFTW library.

How to use

pathf90 -o fftw-test.x -intrinsic=PGI  -I/site/fftw3/include  -L/site/fftw3/lib fftw-test.f  -lfftw3

The -intrinsic=PGI is needed in order to use the rand(0) calling syntax.

     program fftwtest
c     
     include 'fftw3.f'
     parameter (N=4)
     double complex in, out
     dimension in(N), out(N)
     integer i
     integer*8 plan
c     
     do i=1,N
           in(i)=cmplx(rand(0),rand(0))
     enddo
c      
     write(*,110) in
c
     call dfftw_plan_dft_1d(plan,N,in,out,FFTW_FORWARD,FFTW_ESTIMATE)
     call dfftw_execute(plan)      
     write(*,110) out
c
     call dfftw_destroy_plan(plan)
c
110  format(8(f6.2))
c
     end

A testrun using a vector length N=100000000 took 39.4 seconds on a titan node.