title: use fftw3 with gfortran included in TDM-GCC-64
body: <p>I am trying to use <code>FFTW3</code> with <code>gfortran</code> compiler included in the <code>TDM-GCC-64</code> suite in Windows 7 platform.</p>
  
  <p>I have downloaded "fftw-3.3.4-dll64.zip" from the following page:</p>
  
  <p><a href="http://www.fftw.org/install/windows.html" rel="nofollow">http://www.fftw.org/install/windows.html</a></p>
  
  <p>I also created a fortran module described in the following tutorial:</p>
  
  <p><a href="http://www.fftw.org/doc/Defining-an-FFTW-module.html" rel="nofollow">http://www.fftw.org/doc/Defining-an-FFTW-module.html</a></p>
  
  <p>Now, I tried to compile the following fortrans program</p>
  
  <pre><code>program test
  
  use FFTW3 
  
  implicit none
  
  integer N
  parameter(N=4)
  
  integer*8 plan
    double complex in, out
    dimension in(N),out(N)
  
    integer i
  
    write(*,*) 'Input array:'
  
    do i = 1,N,1
      in(i) = dcmplx(float(i),float(i+1))
      write(*,*) '    in(',i,') = ',in(i)
    enddo
  
    call dfftw_plan_dft_1d ( plan, N, in, out, FFTW_FORWARD, FFTW_ESTIMATE )
  
    call dfftw_execute ( plan )
  
    write(*,*) 'Output array:'
    do i = 1,N,1
      write(*,*) '    out(',i,') = ',out(i)
    enddo
  
    call dfftw_destroy_plan ( plan )
  
    call dfftw_plan_dft_1d ( plan, N, out, in, FFTW_FORWARD, FFTW_ESTIMATE )
  
    call dfftw_execute ( plan )
  
    write(*,*) 'Output array after inverse FFT:'
    do i = 1,N,1
      write(*,*) '    ',N,' * in(',i,') = ',in(i)
    enddo
  
    call dfftw_destroy_plan ( plan )
  
    end
  </code></pre>
  
  <p>I tried to compile but the a couple of error messages popped up:</p>
  
  <p>undefined reference to <code>dfftw_plan_dft_1d_'
  undefined reference to</code>dfftw_execute_'
  ...</p>
  
  <p>The command used for compiling is:</p>
  
  <p>gfortran test.f90 -ffree-form -o test_fftw.exe</p>
  
  <p>I searched web up and down but have not found solutions to the problem. Could anyone help me out here? Thanks!!!</p>