# rffti.f

          SUBROUTINE RFFTI (N, WSAVE)
    C***BEGIN PROLOGUE  RFFTI
    ....
    ....
    Warning:   this routine is not intended to be user-callable.
    ....
    ....
    C***SUBSIDIARY
    C***PURPOSE  Initialize a work array for RFFTF and RFFTB.
    C***LIBRARY   SLATEC (FFTPACK)
    C***CATEGORY  J1A1
    C***TYPE      SINGLE PRECISION (RFFTI-S, CFFTI-C)
    C***KEYWORDS  FFTPACK, FOURIER TRANSFORM
    C***AUTHOR  Swarztrauber, P. N., (NCAR)
    C***DESCRIPTION
    C
    C   ********************************************************************
    C   *   NOTICE   NOTICE   NOTICE   NOTICE   NOTICE   NOTICE   NOTICE   *
    C   ********************************************************************
    C   *                                                                  *
    C   *   This routine uses non-standard Fortran 77 constructs and will  *
    C   *   be removed from the library at a future date.  You are         *
    C   *   requested to use RFFTI1.                                       *
    C   *                                                                  *
    C   ********************************************************************
    C
    C   Subroutine RFFTI initializes the array WSAVE which is used in
    C   both RFFTF and RFFTB.  The prime factorization of N together with
    C   a tabulation of the trigonometric functions are computed and
    C   stored in WSAVE.
    C
    C   Input Argument
    C
    C   N       the length of the sequence to be transformed.
    C
    C   Output Argument
    C
    C   WSAVE   a work array which must be dimensioned at least 2*N+15.
    C           The same work array can be used for both RFFTF and RFFTB
    C           as long as N remains unchanged.  Different WSAVE arrays
    C           are required for different values of N.  The contents of
    C           WSAVE must not be changed between calls of RFFTF or RFFTB.
    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  RFFTI1
    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           changing dummy array size declarations (1) to (*).
    C   861211  REVISION DATE from Version 3.2
    C   881128  Modified by Dick Valent to meet prologue standards.
    C   891214  Prologue converted to Version 4.0 format.  (BAB)
    C   900131  Routine changed from user-callable to subsidiary
    C           because of non-standard Fortran 77 arguments in the
    C           call to CFFTB1.  (WRB)
    C   920501  Reformatted the REFERENCES section.  (WRB)
    C***END PROLOGUE  RFFTI