/*  solvru.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.)
 * ------------------------------------------------------------------------
 */
int solvru(double *a,double *b,int n)
{ int j,k; double fabs();
  double s,t,*p,*q;
  for(j=0,s=0.,p=a; j<n ;++j,p+=n+1) if((t=fabs(*p))>s) s=t;
  s*=1.e-16;
  for(j=n-1,p=a+n*n-1; j>=0 ;--j,p-=n+1){
    for(k=j+1,q=p+1; k<n ;) b[j]-=b[k++]* *q++;
    if(fabs(*p)<s) return -1;
    b[j]/= *p;
   }
  return 0;
}