SLATEC Routines --- CFFTI1 ---

*DECK CFFTI1
      SUBROUTINE CFFTI1 (N, WA, IFAC)
C***BEGIN PROLOGUE  CFFTI1
C***PURPOSE  Initialize a real and an integer work array for CFFTF1 and
C            CFFTB1.
C***LIBRARY   SLATEC (FFTPACK)
C***CATEGORY  J1A2
C***TYPE      COMPLEX (RFFTI1-S, CFFTI1-C)
C***KEYWORDS  FFTPACK, FOURIER TRANSFORM
C***AUTHOR  Swarztrauber, P. N., (NCAR)
C***DESCRIPTION
C
C  Subroutine CFFTI1 initializes the work arrays WA and IFAC which are
C  used in both CFFTF1 and CFFTB1.  The prime factorization of N and a
C  tabulation of the trigonometric functions are computed and stored in
C  IFAC and WA, respectively.
C
C  Input Parameter
C
C  N       the length of the sequence to be transformed
C
C  Output Parameters
C
C  WA      a real work array which must be dimensioned at least 2*N.
C
C  IFAC    an integer work array which must be dimensioned at least 15.
C
C          The same work arrays can be used for both CFFTF1 and CFFTB1
C          as long as N remains unchanged.  Different WA and IFAC arrays
C          are required for different values of N.  The contents of
C          WA and IFAC must not be changed between calls of CFFTF1 or
C          CFFTB1.
C
C***REFERENCES  P. N. Swarztrauber, Vectorizing the FFTs, in Parallel
C                 Computations (G. Rodrigue, ed.), Academic Press,
C                 1982, pp. 51-83.
C***ROUTINES CALLED  (NONE)
C***REVISION HISTORY  (YYMMDD)
C   790601  DATE WRITTEN
C   830401  Modified to use SLATEC library source file format.
C   860115  Modified by Ron Boisvert to adhere to Fortran 77 by
C           (a) changing dummy array size declarations (1) to (*),
C           (b) changing references to intrinsic function FLOAT
C               to REAL, and
C           (c) changing definition of variable TPI by using
C               FORTRAN intrinsic function ATAN instead of a DATA
C               statement.
C   881128  Modified by Dick Valent to meet prologue standards.
C   890531  Changed all specific intrinsics to generic.  (WRB)
C   891214  Prologue converted to Version 4.0 format.  (BAB)
C   900131  Routine changed from subsidiary to user-callable.  (WRB)
C   920501  Reformatted the REFERENCES section.  (WRB)
C***END PROLOGUE  CFFTI1