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/* evmax.c CCMATH mathematics library source code.
*
* Copyright (C) 2000 Daniel A. Atkinson All rights reserved.
* This code may be redistributed under the terms of the GNU library
* public license (LGPL). ( See the lgpl.license file for details.)
* ------------------------------------------------------------------------
*/
#include <stdlib.h>
#include "ccmath.h"
double evmax(double *a, double *u, int n)
{
double *p, *q, *qm, *r, *s, *t;
double ev, evm, c, h;
int kc;
q = (double *)calloc(n, sizeof(double));
qm = q + n;
*(qm - 1) = 1.;
ev = 0.;
for (kc = 0; kc < 200; ++kc) {
h = c = 0.;
evm = ev;
for (p = u, r = a, s = q; s < qm;) {
*p = 0.;
for (t = q; t < qm;)
*p += *r++ * *t++;
c += *p * *p;
h += *p++ * *s++;
}
ev = c / h;
c = sqrt(c);
for (p = u, s = q; s < qm;) {
*p /= c;
*s++ = *p++;
}
if (((c = ev - evm) < 0. ? -c : c) < 1.e-16 * (ev < 0. ? -ev : ev)) {
free(q);
return ev;
}
}
free(q);
for (kc = 0; kc < n;)
u[kc++] = 0.;
return 0.;
}
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