SCFFT Routine Documentation

SCFFT (MODE,N,X,COMM,INFO)

SUBROUTINE

INTEGER MODE

Input

The value of MODE on input determines the operation performed by SCFFT. 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. MODE=1 : a real transform is performed. Initializations are assumed to have been performed by a prior call to SCFFT. MODE=2 : initializations and a real transform are performed.

INTEGER N

Input

On input: N is the length of the real sequence X

REAL X(N)

Input/Output

On input: X contains the real sequence of length N to be transformed. On output: X contains the transformed Hermitian sequence.

REAL COMM(3*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 SCFFT(0,N,X,COMM,INFO)
             CALL SCFFT(1,N,X,COMM,INFO)
             DO 10 I = N/2+2, N
                X(I) = -X(I)
        10   CONTINUE
             CALL CSFFT(1,N,X,COMM,INFO)