Node:CFFT1MX, Previous:ZFFT1MX, Up:Multi-1D FFT


CFFT1MX Routine Documentation

CFFT1MX (MODE,SCALE,INPL,NSEQ,N,X,INCX1,INCX2,
Y,INCY1,INCY2,COMM,INFO) 		SUBROUTINE
INTEGER MODE Input
The value of MODE on input determines the operation performed by CFFT1MX.
On input:
  • MODE=0 : only initializations (specific to the value of N) are performed; this is usually followed by calls to the same routine with MODE=-1 or 1.
  • MODE=-1 : a forward transform is performed. Initializations are assumed to have been performed by a prior call to CFFT1MX.
  • MODE=1 : a backward (reverse) transform is performed. Initializations are assumed to have been performed by a prior call to CFFT1MX.
  • MODE=-2 : initializations and a forward transform are performed.
  • MODE=2 : initializations and a backward transform are performed.

REAL SCALE Input
On input: SCALE is the scaling factor to apply to the output sequences

LOGICAL INPL Input
On input: if INPL is .TRUE. then X is overwritten by the output sequences; otherwise the output sequences are returned in Y.

INTEGER NSEQ Input
On input: NSEQ is the number of sequences to be transformed

INTEGER N Input
On input: N is the number of elements in each sequence to be transformed

COMPLEX X(1+(N-1)*INCX1+(NSEQ-1)*INCX2) Input/Output
On input: X contains the NSEQ complex sequences of length N to be transformed; the ith element of sequence j is stored in X(1+(i-1)*INCX1+(j-1)*INCX2).
On output: if INPL is .TRUE. then X contains the transformed sequences in the same locations as on input; otherwise X remains unchanged.

INTEGER INCX1 Input
On input: INCX1 is the increment used to store successive elements of a given sequence in X (INCX1=1 for contiguous data).
Constraint: INCX1 > 0.

INTEGER INCX2 Input
On input: INCX2 is the increment used to store corresponding elements of successive sequences in X (INCX2=N for contiguous data).
Constraint: INCX2 > 0.

COMPLEX Y(1+(N-1)*INCY1+(NSEQ-1)*INCY2) Output
On output: if INPL is .FALSE. then Y contains the transformed sequences with the ith element of sequence j stored in Y(1+(i-1)*INCY1+(j-1)*INCY2); otherwise Y is not referenced.

INTEGER INCY1 Input
On input: INCY1 is the increment used to store successive elements of a given sequence in Y. If INPL is .TRUE. then INCY1 is not referenced.
Constraint: INCY1 > 0.

INTEGER INCY2 Input
On input: INCY2 is the increment used to store corresponding elements of successive sequences in Y (INCY2=N for contiguous data). If INPL is .TRUE. then INCY2 is not referenced.
Constraint: INCY2 > 0.

COMPLEX COMM(5*N+100) Input/Output
COMM is a communication array. Some portions of the array are used to store initializations for subsequent calls with the same sequence length N. The remainder is used as temporary store.

INTEGER INFO Output
On output: INFO is an error indicator. On successful exit, INFO contains 0. If INFO = -i on exit, the i-th argument had an illegal value. 

     Example:
     C     Forward FFTs are performed unscaled and in-place on two
     C     contiguous vectors stored in the first two columns of X.
     C     Manipulations are stored in 2nd and 3rd columns of X which are
     C     then transformed back.
     C
             COMPLEX X(N,3)
             SCALE = 1.0
             INPL = .TRUE.
             CALL CFFT1MX(0,SCALE,INPL,2,N,X,1,N,DUM,1,N,COMM,INFO)
             CALL CFFT1MX(-1,SCALE,INPL,2,N,X,1,N,DUM,1,N,COMM,INFO)
             DO 10 I = 1, N
                X(I,3) = X(I,1)*CONJG(X(I,2))/REAL(N)
                X(I,2) = CMPLX(0.0D0,1.0D0)*X(I,2)/REAL(N)
        10   CONTINUE
             CALL CFFT1MX(1,SCALE,INPL,2,N,X(1,2),1,N,DUM,1,N,COMM,INFO)