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47 lines
1.7 KiB
Fortran
47 lines
1.7 KiB
Fortran
*DECK EZFFTI
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SUBROUTINE EZFFTI (N, WSAVE)
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C***BEGIN PROLOGUE EZFFTI
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C***PURPOSE Initialize a work array for EZFFTF and EZFFTB.
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C***LIBRARY SLATEC (FFTPACK)
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C***CATEGORY J1A1
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C***TYPE SINGLE PRECISION (EZFFTI-S)
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C***KEYWORDS FFTPACK, FOURIER TRANSFORM
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C***AUTHOR Swarztrauber, P. N., (NCAR)
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C***DESCRIPTION
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C
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C Subroutine EZFFTI initializes the work array WSAVE which is used in
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C both EZFFTF and EZFFTB. The prime factorization of N together with
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C a tabulation of the trigonometric functions are computed and
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C stored in WSAVE.
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C
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C Input Parameter
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C
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C N the length of the sequence to be transformed.
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C
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C Output Parameter
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C
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C WSAVE a work array which must be dimensioned at least 3*N+15.
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C The same work array can be used for both EZFFTF and EZFFTB
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C as long as N remains unchanged. Different WSAVE arrays
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C are required for different values of N.
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C
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C***REFERENCES P. N. Swarztrauber, Vectorizing the FFTs, in Parallel
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C Computations (G. Rodrigue, ed.), Academic Press,
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C 1982, pp. 51-83.
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C***ROUTINES CALLED EZFFT1
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C***REVISION HISTORY (YYMMDD)
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C 790601 DATE WRITTEN
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C 830401 Modified to use SLATEC library source file format.
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C 860115 Modified by Ron Boisvert to adhere to Fortran 77 by
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C changing dummy array size declarations (1) to (*).
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C 861211 REVISION DATE from Version 3.2
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C 881128 Modified by Dick Valent to meet prologue standards.
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C 891214 Prologue converted to Version 4.0 format. (BAB)
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C 920501 Reformatted the REFERENCES section. (WRB)
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C***END PROLOGUE EZFFTI
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DIMENSION WSAVE(*)
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C***FIRST EXECUTABLE STATEMENT EZFFTI
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IF (N .EQ. 1) RETURN
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CALL EZFFT1 (N,WSAVE(2*N+1),WSAVE(3*N+1))
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RETURN
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END
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