GRASS GIS 8 Programmer's Manual  8.4.0dev(2024)-f4d8c62acd
hevmax.c
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1 /* hevmax.c CCMATH mathematics library source code.
2  *
3  * Copyright (C) 2000 Daniel A. Atkinson All rights reserved.
4  * This code may be redistributed under the terms of the GNU library
5  * public license (LGPL). ( See the lgpl.license file for details.)
6  * ------------------------------------------------------------------------
7  */
8 
9 #include <stdlib.h>
10 #include "ccmath.h"
11 
12 double hevmax(Cpx *a, Cpx *u, int n)
13 {
14  Cpx *x, *p, h;
15 
16  double e, ep, s, t, te = 1.e-12;
17 
18  int k, j;
19 
20  x = (Cpx *)calloc(n, sizeof(Cpx));
21  x[0].re = 1.;
22  e = 0.;
23  do {
24  for (k = 0, p = a, s = t = 0.; k < n; ++k) {
25  for (j = 0, h.re = h.im = 0.; j < n; ++j, ++p) {
26  h.re += p->re * x[j].re - p->im * x[j].im;
27  h.im += p->im * x[j].re + p->re * x[j].im;
28  }
29  s += h.re * h.re + h.im * h.im;
30  t += h.re * x[k].re + h.im * x[k].im;
31  u[k] = h;
32  }
33  ep = e;
34  e = s / t;
35  s = 1. / sqrt(s);
36  for (k = 0; k < n; ++k) {
37  u[k].re *= s;
38  u[k].im *= s;
39  x[k] = u[k];
40  }
41  } while (fabs(e - ep) > fabs(te * e));
42  free(x);
43  return e;
44 }
double hevmax(Cpx *a, Cpx *u, int n)
Definition: hevmax.c:12
double t
Definition: r_raster.c:39
void free(void *)
Definition: la.h:54
double re
Definition: ccmath.h:39
double im
Definition: ccmath.h:39
#define x