mirror of
https://git.planet-casio.com/Lephenixnoir/OpenLibm.git
synced 2025-01-01 06:23:39 +01:00
65 lines
2.2 KiB
Fortran
65 lines
2.2 KiB
Fortran
*DECK SINTI
|
|
SUBROUTINE SINTI (N, WSAVE)
|
|
C***BEGIN PROLOGUE SINTI
|
|
C***PURPOSE Initialize a work array for SINT.
|
|
C***LIBRARY SLATEC (FFTPACK)
|
|
C***CATEGORY J1A3
|
|
C***TYPE SINGLE PRECISION (SINTI-S)
|
|
C***KEYWORDS FFTPACK, FOURIER TRANSFORM
|
|
C***AUTHOR Swarztrauber, P. N., (NCAR)
|
|
C***DESCRIPTION
|
|
C
|
|
C Subroutine SINTI initializes the array WSAVE which is used in
|
|
C subroutine SINT. The prime factorization of N together with
|
|
C a tabulation of the trigonometric functions are computed and
|
|
C stored in WSAVE.
|
|
C
|
|
C Input Parameter
|
|
C
|
|
C N the length of the sequence to be transformed. The method
|
|
C is most efficient when N+1 is a product of small primes.
|
|
C
|
|
C Output Parameter
|
|
C
|
|
C WSAVE a work array with at least INT(3.5*N+16) locations.
|
|
C Different WSAVE arrays are required for different values
|
|
C of N. The contents of WSAVE must not be changed between
|
|
C calls of SINT.
|
|
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 RFFTI
|
|
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 PI 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 890531 REVISION DATE from Version 3.2
|
|
C 891214 Prologue converted to Version 4.0 format. (BAB)
|
|
C 920501 Reformatted the REFERENCES section. (WRB)
|
|
C***END PROLOGUE SINTI
|
|
DIMENSION WSAVE(*)
|
|
C***FIRST EXECUTABLE STATEMENT SINTI
|
|
IF (N .LE. 1) RETURN
|
|
PI = 4.*ATAN(1.)
|
|
NP1 = N+1
|
|
NS2 = N/2
|
|
DT = PI/NP1
|
|
KS = N+2
|
|
KF = KS+NS2-1
|
|
FK = 0.
|
|
DO 101 K=KS,KF
|
|
FK = FK+1.
|
|
WSAVE(K) = 2.*SIN(FK*DT)
|
|
101 CONTINUE
|
|
CALL RFFTI (NP1,WSAVE(KF+1))
|
|
RETURN
|
|
END
|