/*

 * Implement Heap sort -- direct and indirect sorting

 * Based on descriptions in Sedgewick "Algorithms in C"

 *

 * Copyright (C) 1999  Thomas Walter

 *

 * 18 February 2000: Modified for GSL by Brian Gough

 *

 * This 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, or (at your option) any

 * later version.

 *

 * This source 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.

 */

static inline void FUNCTION (index, downheap) (size_t * p, const BASE * data, const size_t stride, const size_t N, size_t k);

static inline void

FUNCTION (index, downheap) (size_t * p, const BASE * data, const size_t stride, const size_t N, size_t k)

{

  const size_t pki = p[k];

  while (k <= N / 2)

    {

      size_t j = 2 * k;

      if (j < N && data[p[j] * stride] < data[p[j + 1] * stride])

        {

          j++;

        }

      if (!(data[pki * stride] < data[p[j] * stride])) /* avoid infinite loop if nan */

        {

          break;

        }

      p[k] = p[j];

      k = j;

    }

  p[k] = pki;

}

void

FUNCTION (gsl_sort, index) (size_t * p, const BASE * data, const size_t stride, const size_t n)

{

  size_t N;

  size_t i, k;

  if (n == 0)

    {

      return;   /* No data to sort */

    }

  /* set permutation to identity */

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

    {

      p[i] = i ;

    }

  /* We have n_data elements, last element is at 'n_data-1', first at

     '0' Set N to the last element number. */

  N = n - 1;

  k = N / 2;

  k++;                          /* Compensate the first use of 'k--' */

  do

    {

      k--;

      FUNCTION (index, downheap) (p, data, stride, N, k);

    }

  while (k > 0);

  while (N > 0)

    {

      /* first swap the elements */

      size_t tmp = p[0];

      p[0] = p[N];

      p[N] = tmp;

      /* then process the heap */

      N--;

      FUNCTION (index, downheap) (p, data, stride, N, 0);

    }

}

int

FUNCTION (gsl_sort_vector, index) (gsl_permutation * permutation, const TYPE (gsl_vector) * v)

{

  if (permutation->size != v->size)

    {

      GSL_ERROR ("permutation and vector lengths are not equal", GSL_EBADLEN);

    }

  FUNCTION (gsl_sort, index) (permutation->data, v->data, v->stride, v->size) ;

  return GSL_SUCCESS ;

}