/*  ruinv.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 ruinv(double *a,int n)
{ int j; double fabs();
  double tt,z,*p,*q,*r,*s,*t;
  for(j=0,tt=0.,p=a; j<n ;++j,p+=n+1) if((z=fabs(*p))>tt) tt=z;
  tt*=1.e-16;
  for(j=0,p=a; j<n ;++j,p+=n+1){
    if(fabs(*p)<tt) return -1;
    *p=1./ *p;
    for(q=a+j,t=a; q<p ;t+=n+1,q+=n){
      for(s=q,r=t,z=0.; s<p ;s+=n) z-= *s * *r++;
      *q=z* *p;
     }
   }
  return 0;
}