WSJT-X/lib/four2a.f90

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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)
integer*8 plan(NPMAX),nl(NPMAX),nloc
data nplan/0/
common/patience/npatience
include 'fftw3.f90'
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