/* multiroots/convergence.c

 * 

 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Brian Gough

 * 

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 3 of the License, or (at

 * your option) any later version.

 * 

 * This program is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * General Public License for more details.

 * 

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 */

#include <config.h>

#include <gsl/gsl_math.h>

#include <gsl/gsl_errno.h>

#include <gsl/gsl_multiroots.h>

int

gsl_multiroot_test_delta (const gsl_vector * dx, const gsl_vector * x, 

                     double epsabs, double epsrel)

{

  size_t i;

  int ok = 1;

  const size_t n = x->size ;

  if (epsrel < 0.0)

    {

      GSL_ERROR ("relative tolerance is negative", GSL_EBADTOL);

    }

  for (i = 0 ; i < n ; i++)

    {

      double xi = gsl_vector_get(x,i);

      double dxi = gsl_vector_get(dx,i);

      double tolerance = epsabs + epsrel * fabs(xi)  ;

      if (fabs(dxi) < tolerance || dxi == 0)

        {

          ok = 1;

        }

      else

        {

          ok = 0;

          break;

        }

    }

  if (ok)

    return GSL_SUCCESS ;

  return GSL_CONTINUE;

}

int

gsl_multiroot_test_residual (const gsl_vector * f, double epsabs)

{

  size_t i;

  double residual = 0;

  const size_t n = f->size;

  if (epsabs < 0.0)

    {

      GSL_ERROR ("absolute tolerance is negative", GSL_EBADTOL);

    }

  for (i = 0 ; i < n ; i++)

    {

      double fi = gsl_vector_get(f, i);

      residual += fabs(fi);

    }

  if (residual < epsabs)

    {

      return GSL_SUCCESS;

    }

  return GSL_CONTINUE ;

}