CFFT1M Routine Documentation

CFFT1M (MODE,M,N,X,COMM,INFO)

SUBROUTINE

INTEGER MODE

Input

The value of MODE on input determines the operation performed by CFFT1M. 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 : forward transforms are performed. Initializations are assumed to have been performed by a prior call to CFFT1M. MODE=1 : backward (reverse) transforms are performed. Initializations are assumed to have been performed by a prior call to CFFT1M. MODE=-2 : initializations and forward transforms are performed. MODE=2 : initializations and backward transforms are performed.

INTEGER M

Input

On input: M is the number of sequences to be transformed.

INTEGER N

Input

On input: N is the length of the complex sequences in X

COMPLEX X(N*M)

Input/Output

On input: X contains the M complex sequences of length N to be transformed. Element i of sequence j is stored in location i+(j-1)*N of X. On output: X contains the transformed sequences.

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:
             CALL CFFT1M(0,1,N,X,COMM,INFO)
             CALL CFFT1M(-1,2,N,X,COMM,INFO)
             DO 10 I = 1, N
                X(I,3) = X(I,1)*CONJG(X(I,2))
                X(I,2) = CMPLX(0.0D0,1.0D0)*X(I,2)
        10   CONTINUE
             CALL CFFT1M(1,2,N,X(1,2),COMM,INFO)