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- *DECK RFFTI
- SUBROUTINE RFFTI (N, WSAVE)
- C***BEGIN PROLOGUE RFFTI
- 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
- DIMENSION WSAVE(*)
- C***FIRST EXECUTABLE STATEMENT RFFTI
- IF (N .EQ. 1) RETURN
- CALL RFFTI1 (N,WSAVE(N+1),WSAVE(2*N+1))
- RETURN
- END
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