w3ft38.f File Reference

Computes 2.5 x 2.5 n. More...

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Functions/Subroutines
subroutine	w3ft38 (fln, gn, pln, fl, work, trigs)
	Computes 2.5 x 2.5 n.

Detailed Description

Computes 2.5 x 2.5 n.

hemi. grid-scaler

Author

Ralph Jones

Date

1993-07-23

Definition in file w3ft38.f.

Function/Subroutine Documentation

w3ft38()

subroutine w3ft38	(	complex, dimension( 31 , 31 )	fln,
		real, dimension(145,37)	gn,
		real, dimension( 32, 31, 37 )	pln,
		complex, dimension( 31 )	fl,
		real, dimension(144)	work,
		real, dimension(216)	trigs
	)

Computes 2.5 x 2.5 n.

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

Program History Log:

Date	Programmer	Comment
1993-07-23	Ralph Jones	New version of w3ft08(), 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]	FLN	961 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 real work space for subr. w3ft12()
[in]	TRIGS	216 precomputed trig funcs. Used in w3ft12(), computed by w3fa13()
[out]	GN	(145,37) grid values. 5365 point grid is type 29 or 1d hex o.n. 84

Note

w3ft08() 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)         (REAL ON CRAY)
DOUBLE PRECISION COLRA            (REAL ON CRAY)
 
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

Definition at line 53 of file w3ft38.f.