w3ft39.f File Reference

Computes 2.5x2.5 n. More...

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Functions/Subroutines
subroutine	w3ft39 (vln, gn, pln, fl, work, trigs, rcos)
	Computes 2.5 x 2.5 n.

Detailed Description

Computes 2.5x2.5 n.

hemi. grid-vector.

Author

Ralph Jones

Date

1993-07-23

Definition in file w3ft39.f.

Function/Subroutine Documentation

w3ft39()

subroutine w3ft39	(	complex, dimension( 32 , 31 )	vln,
		real, dimension(145,37)	gn,
		real, dimension( 32, 31, 37 )	pln,
		complex, dimension( 31 )	fl,
		real, dimension(144)	work,
		real, dimension(216)	trigs,
		real, dimension(37)	rcos
	)

Computes 2.5 x 2.5 n.

hemi. grid of 145 x 37 points from spectral coefficients in a rhomboidal 30 resolution representing a vector field.

Program History Log:

Date	Programmer	Comment
1993-07-23	Ralph Jones	New version of w3ft09(), takes out w3fa12()

makes pln 3 dimensions, pln is computed one time in main program, trades memory for more speed. w3fa12() used 70% of cpu time.

Parameters

[in]	VLN	992 complex coeff.
[in]	PLN	(32,31,37) real space with legendre polynomials computed by w3fa12().
[in]	FL	31 complex space for fourier coeff.
[in]	WORK	144 work space for subr. w3ft12()
[in]	TRIGS	216 precomputed trig funcs. used in w3ft12, computed by w3fa13().
[in]	RCOS	37 reciprocal cosine latitudes of 2.5 x 2.5 grid must be computed before first call to w3ft11 using sr w3fa13().
[out]	GN	(145,37) grid values. 5365 point grid is type 29 or 1d o.n. 84

Note

w3ft09() was optimized to run in a small amount of memory, it was not optimized for speed, 70 percent of the time was used by subroutine w3fa12() computing the legendre polynomials. Since the legendre polynomials are constant they need to be computed only once in a program. By moving w3fa12() to the main program and computing pln as a (32,31,37) array and changing this subroutine to use pln as a three dimension array the running time was cut 70 percent. Add following code to main program to compute eps, pln, trigs, and rcos one time in program.

DOUBLE PRECISION EPS(992)
DOUBLE PRECISION COLRA
 
REAL             PLN( 32, 31, 37 )
REAL             RCOS(37)
REAL             TRIGS(216)
 
DATA  pi /3.14159265/
 
drad = 2.5 * pi / 180.0
CALL w3fa11(eps,30)
CALL w3fa13(trigs,rcos)
DO lat = 1,37
  colra = (lat - 1) * drad
  CALL w3fa12 (pln(1,1,lat), colra, 30, eps)
END DO

Author

Ralph Jones

Date

1993-07-23

Definition at line 57 of file w3ft39.f.