inverse2_2d Subroutine

  subroutine inverse2_2d (phixf, phi, nny, nnx)
    use fft_work, only: FFT_TO_SPECTRAL_SPACE, delete_fft, init_rcfftw
    use kt_grids, only: naky, nakx => ntheta0, aky
    use job_manage, only: time_message
    use fft_work, only: time_fft
    implicit none
    real, intent(in) :: phixf(:,:)
    complex, intent(out) :: phi(:,:)
    integer, intent(in) :: nnx, nny
    complex, allocatable :: aphi(:,:)
    real, allocatable :: phix(:,:)
    real :: fac
    integer :: ik, it
    type (fft_type) :: xf2d

    !May be inefficient to create and destroy this fft plan
    !on every call to the routine. We may want to move this
    !variable to module level and check its created flag.
#if FFT == _FFTW3_
    call init_rcfftw (xf2d, FFT_TO_SPECTRAL_SPACE, nny, nnx, 1)
#endif    

    allocate (aphi (nny/2+1, nnx))
    allocate (phix (nny, nnx))
    phix(:,:)=0.; aphi(:,:)=cmplx(0.,0.)

    phix(:,:)=transpose(phixf(:,:))

    ! transform
    call time_message(.false., time_fft, ' FFT')
#if FFT == _FFTW3_
    call FFTW_PREFIX(_execute_dft_r2c) (xf2d%plan, phix, aphi)
#endif
    call time_message(.false., time_fft, ' FFT')

    ! scale, dealias and transpose
    do it=1,nakx
       do ik=1,naky
          fac = 2.0
          if (aky(ik) < epsilon(0.0)) fac = 1.0
          phi(it,ik) = aphi(ik,it)*fac*xf2d%scale
       end do
    end do

    deallocate (aphi, phix)
    !RN> this statement causes error for lahey with DEBUG. I don't know why
    !<DD>Reinstating after discussion with RN, if this causes anyone an issue
    !    then we can guard this line with some directives.   
    call delete_fft(xf2d)
  end subroutine inverse2_2d