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.
! This version of four2a makes calls to the FFTW library to do the
! actual computations.
use fftw3
parameter (NPMAX=2100) !Max numberf of stored plans
parameter (NSMALL=16385) !Max half complex size of "small" FFTs
complex a(nfft) !Array to be transformed
complex aa(NSMALL) !Local copy of "small" a()
integer nn(NPMAX),ns(NPMAX),nf(NPMAX) !Params of stored plans
integer*8 nl(NPMAX),nloc !More params of plans
integer*8 plan(NPMAX) !Pointers to stored plans
logical found_plan
data nplan/0/ !Number of stored plans
common/patience/npatience,nthreads !Patience and threads for FFTW plans
save plan,nplan,nn,ns,nf,nl
if(nfft.lt.0) go to 999
nloc=loc(a)
found_plan = .false.
!$omp critical(four2a_setup)
do i=1,nplan
if(nfft.eq.nn(i) .and. isign.eq.ns(i) .and. &
iform.eq.nf(i) .and. nloc.eq.nl(i)) then
found_plan = .true.
exit
end if
enddo
if(i.ge.NPMAX) stop 'Too many FFTW plans requested.'
if (.not. found_plan) then
nplan=nplan+1
i=nplan
nn(i)=nfft
ns(i)=isign
nf(i)=iform
nl(i)=nloc
! Planning: FFTW_ESTIMATE, FFTW_ESTIMATE_PATIENT, FFTW_MEASURE,
! FFTW_PATIENT, FFTW_EXHAUSTIVE
nflags=FFTW_ESTIMATE
if(npatience.eq.1) nflags=FFTW_ESTIMATE_PATIENT
if(npatience.eq.2) nflags=FFTW_MEASURE
if(npatience.eq.3) nflags=FFTW_PATIENT
if(npatience.eq.4) nflags=FFTW_EXHAUSTIVE
if(nfft.le.NSMALL) then
jz=nfft
if(iform.le.0) jz=nfft/2+1
aa(1:jz)=a(1:jz)
endif
!$omp critical(fftw) ! serialize non thread-safe FFTW3 calls
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
!$omp end critical(fftw)
if(nfft.le.NSMALL) then
jz=nfft
if(iform.le.0) jz=nfft/2+1
a(1:jz)=aa(1:jz)
endif
end if
!$omp end critical(four2a_setup)
call sfftw_execute(plan(i))
return
999 continue
!$omp critical(four2a)
do i=1,nplan
! The test is only to silence a compiler warning:
if(ndim.ne.-999) then
!$omp critical(fftw) ! serialize non thread-safe FFTW3 calls
call sfftw_destroy_plan(plan(i))
!$omp end critical(fftw)
end if
enddo
nplan=0
!$omp end critical(four2a)
return
end subroutine four2a