/* linalg/test_common.c
 *
 * Copyright (C) 2017, 2018, 2019, 2020 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_random_matrix(gsl_matrix * m, 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_random_complex_vector(gsl_vector_complex * v, gsl_rng * r)
{
  const size_t N = v->size;
  size_t i;

  for (i = 0; i < N; ++i)
    {
      gsl_complex vi;
      GSL_REAL(vi) = gsl_rng_uniform(r);
      GSL_IMAG(vi) = gsl_rng_uniform(r);
      gsl_vector_complex_set(v, i, vi);
    }

  return GSL_SUCCESS;
}

static int
create_random_matrix(gsl_matrix * m, gsl_rng * r)
{
  const size_t M = m->size1;
  const size_t N = m->size2;
  size_t i, j;

  for (i = 0; i < M; ++i)
    {
      for (j = 0; j < N; ++j)
        {
          double mij = gsl_rng_uniform(r);
          gsl_matrix_set(m, i, j, mij);
        }
    }

  return GSL_SUCCESS;
}

static int
create_random_complex_matrix(gsl_matrix_complex * m, gsl_rng * r)
{
  const size_t M = m->size1;
  const size_t N = m->size2;
  size_t i, j;

  for (i = 0; i < M; ++i)
    {
      for (j = 0; j < N; ++j)
        {
          gsl_complex mij;

          GSL_REAL(mij) = gsl_rng_uniform(r);
          GSL_IMAG(mij) = gsl_rng_uniform(r);

          gsl_matrix_complex_set(m, i, j, mij);
        }
    }

  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(CblasLower, CblasUnit, m, m);

  return GSL_SUCCESS;
}

static int
create_herm_matrix(gsl_matrix_complex * 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 re = gsl_rng_uniform(r);
          double im = (i != j) ? gsl_rng_uniform(r) : 0.0;
          gsl_complex z = gsl_complex_rect(re, im);

          gsl_matrix_complex_set(m, i, j, z);

          if (i != j)
            gsl_matrix_complex_set(m, j, i, gsl_complex_conjugate(z));
        }
    }

  return GSL_SUCCESS;
}

/* create symmetric banded matrix with p sub/super-diagonals */
static int
create_symm_band_matrix(const size_t p, gsl_matrix * m, gsl_rng * r)
{
  size_t i;

  gsl_matrix_set_zero(m);

  for (i = 0; i < p + 1; ++i)
    {
      gsl_vector_view subdiag = gsl_matrix_subdiagonal(m, i);
      create_random_vector(&subdiag.vector, r);

      if (i > 0)
        {
          gsl_vector_view superdiag = gsl_matrix_superdiagonal(m, i);
          gsl_vector_memcpy(&superdiag.vector, &subdiag.vector);
        }
    }

  return GSL_SUCCESS;
}

/* create (p,q) banded matrix */
static int
create_band_matrix(const size_t p, const size_t q, gsl_matrix * m, gsl_rng * r)
{
  size_t i;

  gsl_matrix_set_zero(m);

  for (i = 0; i <= p; ++i)
    {
      gsl_vector_view v = gsl_matrix_subdiagonal(m, i);
      create_random_vector(&v.vector, r);
    }

  for (i = 1; i <= q; ++i)
    {
      gsl_vector_view v = gsl_matrix_superdiagonal(m, i);
      create_random_vector(&v.vector, r);
    }

  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_posdef_complex_matrix(gsl_matrix_complex *m, gsl_rng *r)
{
  const size_t N = m->size1;
  const double alpha = 10.0 * N;
  size_t i;

  create_herm_matrix(m, r);

  for (i = 0; i < N; ++i)
    {
      gsl_complex * mii = gsl_matrix_complex_ptr(m, i, i);
      GSL_REAL(*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;
}

static int
create_posdef_band_matrix(const size_t p, 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_band_matrix(p, m, r);

  for (i = 0; i < N; ++i)
    {
      double *mii = gsl_matrix_ptr(m, i, i);
      *mii += alpha;
    }

  return GSL_SUCCESS;
}

/* transform dense symmetric banded matrix to compact form, with bandwidth p */
static int
symm2band_matrix(const size_t p, const gsl_matrix * m, gsl_matrix * bm)
{
  const size_t N = m->size1;

  if (bm->size1 != N)
    {
      GSL_ERROR("banded matrix requires N rows", GSL_EBADLEN);
    }
  else if (bm->size2 != p + 1)
    {
      GSL_ERROR("banded matrix requires p + 1 columns", GSL_EBADLEN);
    }
  else
    {
      size_t i;

      gsl_matrix_set_zero(bm);

      for (i = 0; i < p + 1; ++i)
        {
          gsl_vector_const_view diag = gsl_matrix_const_subdiagonal(m, i);
          gsl_vector_view v = gsl_matrix_subcolumn(bm, i, 0, N - i);

          gsl_vector_memcpy(&v.vector, &diag.vector);
        }

      return GSL_SUCCESS;
    }
}

/* transform general dense (p,q) banded matrix to compact banded form */
static int
gen2band_matrix(const size_t p, const size_t q, const gsl_matrix * A, gsl_matrix * AB)
{
  const size_t N = A->size2;

  if (AB->size1 != N)
    {
      GSL_ERROR("banded matrix requires N rows", GSL_EBADLEN);
    }
  else if (AB->size2 != 2*p + q + 1)
    {
      GSL_ERROR("banded matrix requires 2*p + q + 1 columns", GSL_EBADLEN);
    }
  else
    {
      size_t i;

      gsl_matrix_set_zero(AB);

      /* copy diagonal and subdiagonals */
      for (i = 0; i <= p; ++i)
        {
          gsl_vector_const_view v = gsl_matrix_const_subdiagonal(A, i);
          gsl_vector_view w = gsl_matrix_subcolumn(AB, p + q + i, 0, v.vector.size);
          gsl_vector_memcpy(&w.vector, &v.vector);
        }

      /* copy superdiagonals */
      for (i = 1; i <= q; ++i)
        {
          gsl_vector_const_view v = gsl_matrix_const_superdiagonal(A, i);
          gsl_vector_view w = gsl_matrix_subcolumn(AB, p + q - i, i, v.vector.size);
          gsl_vector_memcpy(&w.vector, &v.vector);
        }

      return GSL_SUCCESS;
    }
}