/* linalg/test_common.c

 *

 * Copyright (C) 2017 Patrick Alken

 * 

 * 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 <stdlib.h>

#include <gsl/gsl_math.h>

#include <gsl/gsl_blas.h>

#include <gsl/gsl_matrix.h>

#include <gsl/gsl_vector.h>

#include <gsl/gsl_rng.h>

static int create_random_vector(gsl_vector * v, gsl_rng * r);

static int create_posdef_matrix(gsl_matrix * m, gsl_rng * r);

static int create_hilbert_matrix2(gsl_matrix * m);

static int

create_random_vector(gsl_vector * v, gsl_rng * r)

{

  const size_t N = v->size;

  size_t i;

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

    {

      double vi = gsl_rng_uniform(r);

      gsl_vector_set(v, i, vi);

    }

  return GSL_SUCCESS;

}

static int

create_symm_matrix(gsl_matrix * m, gsl_rng * r)

{

  const size_t N = m->size1;

  size_t i, j;

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

    {

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

        {

          double mij = gsl_rng_uniform(r);

          gsl_matrix_set(m, i, j, mij);

        }

    }

  /* copy lower triangle to upper */

  gsl_matrix_transpose_tricpy('L', 0, m, m);

  return GSL_SUCCESS;

}

static int

create_posdef_matrix(gsl_matrix * m, gsl_rng * r)

{

  const size_t N = m->size1;

  const double alpha = 10.0 * N;

  size_t i;

  /* The idea is to make a symmetric diagonally dominant

   * matrix. Make a symmetric matrix and add alpha*I to

   * its diagonal */

  create_symm_matrix(m, r);

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

    {

      double mii = gsl_matrix_get(m, i, i);

      gsl_matrix_set(m, i, i, mii + alpha);

    }

  return GSL_SUCCESS;

}

static int

create_hilbert_matrix2(gsl_matrix * m)

{

  const size_t N = m->size1;

  size_t i, j;

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

    {

      for (j = 0; j < N; j++)

        {

          gsl_matrix_set(m, i, j, 1.0/(i+j+1.0));

        }

    }

  return GSL_SUCCESS;

}