[TEST]UPSTREAM: Pick some source changes from 48080d0a97

* Sync new folder structure

AMSS_NCKU_source/AHF_Direct/FFT.f90

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+
+
+#if 0
+program checkFFT
+use dfport
+implicit none
+double precision::x
+integer,parameter::N=256
+double precision,dimension(N*2)::p
+double precision,dimension(N/2)::s
+integer::ncount,j,idum
+character(len=8)::tt
+tt=clock()
+idum=iachar(tt(8:8))-48
+p=0.0
+open(77,file='prime.dat',status='unknown')
+loop1:do ncount=1,N
+   x=ran(idum)
+   p(2*ncount-1)=x
+   write(77,'(f15.3)')x
+enddo loop1
+close(77)
+call four1(p,N,1)
+do j=1,N/2
+  s(j)=p(2*j)*p(2*j)+p(2*j-1)*p(2*j-1)
+enddo
+x=0.0
+do j=1,N/2
+  x=x+s(j)
+enddo
+s=s/x
+open(77,file='power.dat',status='unknown')
+do j=1,N/2
+  write(77,'(2(1x,f15.3))')dble(j-1)/dble(N),s(j)
+enddo
+close(77)
+end program checkFFT
+#endif
+
+!-------------
+! Optimized FFT using Intel oneMKL DFTI
+! Mathematical equivalence: Standard DFT definition
+!   Forward (isign=1):  X[k] = sum_{n=0}^{N-1} x[n] * exp(-2*pi*i*k*n/N)
+!   Backward (isign=-1): X[k] = sum_{n=0}^{N-1} x[n] * exp(+2*pi*i*k*n/N)
+! Input/Output: dataa is interleaved complex array [Re(0),Im(0),Re(1),Im(1),...]
+!-------------
+SUBROUTINE four1(dataa,nn,isign)
+use MKL_DFTI
+implicit none
+INTEGER, intent(in) :: isign, nn
+DOUBLE PRECISION, dimension(2*nn), intent(inout) :: dataa
+
+type(DFTI_DESCRIPTOR), pointer :: desc
+integer :: status
+
+! Create DFTI descriptor for 1D complex-to-complex transform
+status = DftiCreateDescriptor(desc, DFTI_DOUBLE, DFTI_COMPLEX, 1, nn)
+if (status /= 0) return
+
+! Set input/output storage as interleaved complex (default)
+status = DftiSetValue(desc, DFTI_PLACEMENT, DFTI_INPLACE)
+if (status /= 0) then
+   status = DftiFreeDescriptor(desc)
+   return
+endif
+
+! Commit the descriptor
+status = DftiCommitDescriptor(desc)
+if (status /= 0) then
+   status = DftiFreeDescriptor(desc)
+   return
+endif
+
+! Execute FFT based on direction
+if (isign == 1) then
+   ! Forward FFT: exp(-2*pi*i*k*n/N)
+   status = DftiComputeForward(desc, dataa)
+else
+   ! Backward FFT: exp(+2*pi*i*k*n/N)
+   status = DftiComputeBackward(desc, dataa)
+endif
+
+! Free descriptor
+status = DftiFreeDescriptor(desc)
+
+return
+END SUBROUTINE four1