subroutine four2a(a,nfft,ndim,isign,iform) ! IFORM = 1, 0 or -1, as data is ! complex, real, or the first half of a complex array. Transform ! values are returned in array DATA. They are complex, real, or ! the first half of a complex array, as IFORM = 1, -1 or 0. ! The transform of a real array (IFORM = 0) dimensioned N(1) by N(2) ! by ... will be returned in the same array, now considered to ! be complex of dimensions N(1)/2+1 by N(2) by .... Note that if ! IFORM = 0 or -1, N(1) must be even, and enough room must be ! reserved. The missing values may be obtained by complex conjugation. ! The reverse transformation of a half complex array dimensioned ! N(1)/2+1 by N(2) by ..., is accomplished by setting IFORM ! to -1. In the N array, N(1) must be the true N(1), not N(1)/2+1. ! The transform will be real and returned to the input array. parameter (NPMAX=100) parameter (NSMALL=16384) complex a(nfft) complex aa(NSMALL) integer nn(NPMAX),ns(NPMAX),nf(NPMAX),nl(NPMAX) integer*8 plan(NPMAX) !Actually should be i*8, but no matter ! data nplan/0/,npatience/1/ data nplan/0/,npatience/0/ include 'fftw3.f' save plan,nplan,nn,ns,nf,nl if(nfft.lt.0) go to 999 nloc=loc(a) do i=1,nplan if(nfft.eq.nn(i) .and. isign.eq.ns(i) .and. & iform.eq.nf(i) .and. nloc.eq.nl(i)) go to 10 enddo if(nplan.ge.NPMAX) stop 'Too many FFTW plans requested.' nplan=nplan+1 i=nplan nn(i)=nfft ns(i)=isign nf(i)=iform nl(i)=nloc ! Planning: FFTW_ESTIMATE, FFTW_ESTIMATE_PATIENT, FFTW_MEASURE, ! FFTW_PATIENT, FFTW_EXHAUSTIVE nflags=FFTW_ESTIMATE if(npatience.eq.1) nflags=FFTW_ESTIMATE_PATIENT if(npatience.eq.2) nflags=FFTW_MEASURE if(npatience.eq.3) nflags=FFTW_PATIENT if(npatience.eq.4) nflags=FFTW_EXHAUSTIVE if(nfft.le.NSMALL) then jz=nfft if(iform.eq.0) jz=nfft/2 do j=1,jz aa(j)=a(j) enddo endif if(isign.eq.-1 .and. iform.eq.1) then call sfftw_plan_dft_1d(plan(i),nfft,a,a,FFTW_FORWARD,nflags) else if(isign.eq.1 .and. iform.eq.1) then call sfftw_plan_dft_1d(plan(i),nfft,a,a,FFTW_BACKWARD,nflags) else if(isign.eq.-1 .and. iform.eq.0) then call sfftw_plan_dft_r2c_1d(plan(i),nfft,a,a,nflags) else if(isign.eq.1 .and. iform.eq.-1) then call sfftw_plan_dft_c2r_1d(plan(i),nfft,a,a,nflags) else stop 'Unsupported request in four2a' endif i=nplan if(nfft.le.NSMALL) then jz=nfft if(iform.eq.0) jz=nfft/2 do j=1,jz a(j)=aa(j) enddo endif 10 continue call sfftw_execute(plan(i)) return 999 do i=1,nplan ! The test is only to silence a compiler warning: if(ndim.ne.-999) call sfftw_destroy_plan(plan(i)) enddo return end subroutine four2a