CFFTI(3)

SYNOPSIS
SUBROUTINE CFFTI (N, WSAVE)

NAME
cffti - Initialize a work array for CFFTF and CFFTB.

LIBRARY
SLATEC (FFTPACK)

CATEGORY
J1A2

TYPE
COMPLEX (RFFTI-S, CFFTI-C)

KEYWORDS
FFTPACK, FOURIER TRANSFORM

AUTHOR
Swarztrauber, P. N., (NCAR)

DESCRIPTION
******************************************************************** * NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE * ******************************************************************** * * * This routine uses non-standard Fortran 77 constructs and will * * be removed from the library at a future date. You are * * requested to use CFFTI1. * * * ******************************************************************** Subroutine CFFTI initializes the array WSAVE which is used in both CFFTF and CFFTB. The prime factorization of N together with a tabulation of the trigonometric functions are computed and stored in WSAVE. Input Parameter N the length of the sequence to be transformed Output Parameter WSAVE a work array which must be dimensioned at least 4*N+15. The same work array can be used for both CFFTF and CFFTB as long as N remains unchanged. Different WSAVE arrays are required for different values of N. The contents of WSAVE must not be changed between calls of CFFTF or CFFTB.

REFERENCES
P. N. Swarztrauber, Vectorizing the FFTs, in Parallel Computations (G. Rodrigue, ed.), Academic Press, 1982, pp. 51-83.

ROUTINES CALLED
CFFTI1

REVISION HISTORY (YYMMDD)
790601 DATE WRITTEN
830401 Modified to use SLATEC library source file format.
860115 Modified by Ron Boisvert to adhere to Fortran 77 by changing dummy array size declarations (1) to (*).
861211 REVISION DATE from Version 3.2
881128 Modified by Dick Valent to meet prologue standards.
891214 Prologue converted to Version 4.0 format. (BAB)
900131 Routine changed from user-callable to subsidiary because of non-standard Fortran 77 arguments in the call to CFFTB1. (WRB)
920501 Reformatted the REFERENCES section. (WRB)