asc26 amss-ncku initialized

AMSS_NCKU_source/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
+
+!-------------
+SUBROUTINE four1(dataa,nn,isign)
+implicit none
+INTEGER::isign,nn
+double precision,dimension(2*nn)::dataa
+INTEGER::i,istep,j,m,mmax,n
+double precision::tempi,tempr
+DOUBLE PRECISION::theta,wi,wpi,wpr,wr,wtemp
+n=2*nn
+j=1
+do i=1,n,2
+  if(j.gt.i)then
+     tempr=dataa(j)
+     tempi=dataa(j+1)
+     dataa(j)=dataa(i)
+     dataa(j+1)=dataa(i+1)
+     dataa(i)=tempr
+     dataa(i+1)=tempi
+  endif
+  m=nn
+1 if ((m.ge.2).and.(j.gt.m)) then
+  j=j-m
+  m=m/2
+goto 1
+  endif
+j=j+m
+enddo
+mmax=2
+2  if (n.gt.mmax) then
+     istep=2*mmax
+     theta=6.28318530717959d0/(isign*mmax)
+     wpr=-2.d0*sin(0.5d0*theta)**2
+     wpi=sin(theta)
+     wr=1.d0
+     wi=0.d0
+     do m=1,mmax,2
+       do i=m,n,istep
+         j=i+mmax
+         tempr=sngl(wr)*dataa(j)-sngl(wi)*dataa(j+1)
+         tempi=sngl(wr)*dataa(j+1)+sngl(wi)*dataa(j)
+         dataa(j)=dataa(i)-tempr
+         dataa(j+1)=dataa(i+1)-tempi
+         dataa(i)=dataa(i)+tempr
+         dataa(i+1)=dataa(i+1)+tempi
+       enddo
+          wtemp=wr
+          wr=wr*wpr-wi*wpi+wr
+          wi=wi*wpr+wtemp*wpi+wi
+     enddo
+mmax=istep
+goto 2
+endif
+return
+END SUBROUTINE four1