dbl_sortrus.c

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/****************************************************************************/
/*                                                                          */
/*  This file is part of QSopt_ex.                                          */
/*                                                                          */
/*  (c) Copyright 2006 by David Applegate, William Cook, Sanjeeb Dash,      */
/*  and Daniel Espinoza                                                     */
/*                                                                          */
/*  Sanjeeb Dash ownership of copyright in QSopt_ex is derived from his     */
/*  copyright in QSopt.                                                     */
/*                                                                          */
/*  This code may be used under the terms of the GNU General Public License */
/*  (Version 2.1 or later) as published by the Free Software Foundation.    */
/*                                                                          */
/*  Alternatively, use is granted for research purposes only.               */
/*                                                                          */
/*  It is your choice of which of these two licenses you are operating      */
/*  under.                                                                  */
/*                                                                          */
/*  We make no guarantees about the correctness or usefulness of this code. */
/*                                                                          */
/****************************************************************************/

/* RCSINFO $Id: dbl_sortrus.c,v 1.2 2003/11/05 16:47:22 meven Exp $ */
/****************************************************************************/
/*                                                                          */
/*  This file is part of CONCORDE                                           */
/*                                                                          */
/*  (c) Copyright 1995--1999 by David Applegate, Robert Bixby,              */
/*  Vasek Chvatal, and William Cook                                         */
/*                                                                          */
/*  Permission is granted for academic research use.  For other uses,       */
/*  contact the authors for licensing options.                              */
/*                                                                          */
/*  Use at your own risk.  We make no guarantees about the                  */
/*  correctness or usefulness of this code.                                 */
/*                                                                          */
/****************************************************************************/

/****************************************************************************/
/*                                                                          */
/*                         SORTING ROUTINES                                 */
/*                                                                          */
/*                             TSP CODE                                     */
/*                                                                          */
/*   Written by:  Applegate, Bixby, Chvatal, and Cook                       */
/*   DATE:  February 24, 1994                                               */
/*                                                                          */
/*    EXPORTED FUNCTIONS:                                                   */
/*                                                                          */
/*  char *ILLutil_linked_radixsort (char *data, char *datanext,              */
/*      char *dataval, int valsize)                                         */
/*    USAGE:                                                                */
/*      head = (bar *) ILLutil_linked_radixsort ((char *) head,              */
/*         (char *) &(head->next), (char *) &(head->val), sizeof (int));    */
/*    Then head is the start of the linked list in increasing order of      */
/*    val, with next as the field that links the bars.                      */
/*    WARNING: DOES NOT HANDLE NEGATIVE NUMBERS PROPERLY.                   */
/*                                                                          */
/*  void ILLutil_int_array_quicksort (int *len, int n)                       */
/*    len - the array to be sorted                                          */
/*    n - the number of elements in len                                     */
/*    Uses quicksort to put len in increasing order.                        */
/*                                                                          */
/*  void ILLutil_int_perm_quicksort (int *perm, int *len, int n)             */
/*    perm - must be allocated and initialized by the calling routine,      */
/*           it will be arranged in increasing order of len.                */
/*    n - the number of elements in perm and len.                           */
/*                                                                          */
/*  void ILLutil_double_perm_quicksort (int *perm, double *len, int n)       */
/*    perm - must be allocated and initialized by the calling routine,      */
/*           it will be arranged in increasing order of len.                */
/*    n - the number of elements in perm and len.                           */
/*                                                                          */
/*  void ILLutil_rselect (int *arr, int l, int r, int m,                     */
/*      double *coord, ILLrandstate *rstate)                                 */
/*    arr - permutation that will be rearranged                             */
/*    l,r - specify the range of arr that we are interested in              */
/*    m - is the index into l,r that is the break point for the perm        */
/*    coord - gives the keys that determine the ordering                    */
/*                                                                          */
/****************************************************************************/

#include "qs_config.h"
#include "machdefs.h"
#include "dbl_util.h"
#include "except.h"
#ifdef USEDMALLOC
#include "dmalloc.h"
#endif


#define dbl_BITS_PER_PASS (8)

#define dbl_NBINS (1<<dbl_BITS_PER_PASS)


static void dbl_select_EGlpNum_split (
  int *arr,
  int n,
  double * v,
  int *start,
  int *end,
  double * coord),
  dbl_select_EGlpNum_sort (
  int *arr,
  int n,
  double * coord),
  dbl_select_EGlpNum_sort_dsample (
  double * samp,
  int n);

void dbl_ILLutil_EGlpNum_perm_quicksort (
  int *perm,
  double * len,
  int n)
{
  int i, j, temp;
  double t;

  if (n <= 1)
    return;

  dbl_EGlpNumInitVar (t);
  dbl_ILL_SWAP (perm[0], perm[(n - 1) / 2], temp);

  i = 0;
  j = n;
  dbl_EGlpNumCopy (t, len[perm[0]]);

  for (;;)
  {
    do
      i++;
    while (i < n && dbl_EGlpNumIsLess (len[perm[i]], t));
    do
      j--;
    while (dbl_EGlpNumIsLess (t, len[perm[j]]));
    if (j < i)
      break;
    dbl_ILL_SWAP (perm[i], perm[j], temp);
  }
  dbl_ILL_SWAP (perm[0], perm[j], temp);

  dbl_EGlpNumClearVar (t);
  dbl_ILLutil_EGlpNum_perm_quicksort (perm, len, j);
  dbl_ILLutil_EGlpNum_perm_quicksort (perm + i, len, n - i);
}

/**********  Median - Select Routines **********/

/* dbl_NSAMPLES should be odd */
#define dbl_NSAMPLES 3
#define dbl_SORTSIZE 20


void dbl_ILLutil_EGlpNum_rselect (
  int *arr,
  int l,
  int r,
  int m,
  double * coord,
  ILLrandstate * rstate)
{
  double *samplevals = dbl_EGlpNumAllocArray (dbl_NSAMPLES);
  int i;
  int st, en;
  int n;

  arr += l;
  n = r - l + 1;
  m -= l;

  while (n > dbl_SORTSIZE)
  {
    for (i = 0; i < dbl_NSAMPLES; i++)
    {
      dbl_EGlpNumCopy (samplevals[i], coord[arr[ILLutil_lprand (rstate) % n]]);
    }
    dbl_select_EGlpNum_sort_dsample (samplevals, dbl_NSAMPLES);
    dbl_select_EGlpNum_split (arr, n, &(samplevals[(dbl_NSAMPLES - 1) / 2]),
                          &st, &en, coord);
    if (st > m)
    {
      n = st;
    }
    else if (en <= m)
    {
      arr += en;
      n -= en;
      m -= en;
    }
    else
    {
      return;
    }
  }

  dbl_select_EGlpNum_sort (arr, n, coord);
  dbl_EGlpNumFreeArray (samplevals);
  return;
}

static void dbl_select_EGlpNum_split (
  int *arr,
  int n,
  double * v,
  int *start,
  int *end,
  double * coord)
{
  int i, j, k;
  int t;

  i = 0;
  j = k = n;

  while (i < j)
  {
    if (dbl_EGlpNumIsLess (coord[arr[i]], *v))
    {
      i++;
    }
    else if (dbl_EGlpNumIsEqqual (coord[arr[i]], *v))
    {
      j--;
      dbl_ILL_SWAP (arr[i], arr[j], t);
    }
    else
    {
      j--;
      k--;
      t = arr[i];
      arr[i] = arr[j];
      arr[j] = arr[k];
      arr[k] = t;
    }
  }
  *start = j;
  *end = k;
  return;
}

static void dbl_select_EGlpNum_sort (
  int *arr,
  int n,
  double * coord)
{
  int i, j;
  int t;

  for (i = 1; i < n; i++)
  {
    t = arr[i];
    for (j = i; j > 0 && dbl_EGlpNumIsLess (coord[t], coord[arr[j - 1]]); j--)
    {
      arr[j] = arr[j - 1];
    }
    arr[j] = t;
  }
}

static void dbl_select_EGlpNum_sort_dsample (
  double * samp,
  int n)
{
  int i, j;
  double t;

  dbl_EGlpNumInitVar (t);

  for (i = 1; i < n; i++)
  {
    dbl_EGlpNumCopy (t, samp[i]);
    for (j = i; j > 0 && dbl_EGlpNumIsLess (t, samp[j - 1]); j--)
    {
      dbl_EGlpNumCopy (samp[j], samp[j - 1]);
    }
    dbl_EGlpNumCopy (samp[j], t);
  }
  dbl_EGlpNumClearVar (t);
}

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