fn_group_classes.hpp

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// Copyright (C) 2011 the authors listed below
// http://ecocpak.sourceforge.net
//
// Authors:
// - Dimitrios Bouzas (bouzas at ieee dot org)
// - Nikolaos Arvanitopoulos (niarvani at ieee dot org)
// - Anastasios Tefas (tefas at aiia dot csd dot auth dot gr)
//
// This file is part of the ECOC PAK C++ library. It is
// provided without any warranty of fitness for any purpose.
//
// You can redistribute this file and/or modify it under
// the terms of the GNU Lesser General Public License (LGPL)
// as published by the Free Software Foundation, either
// version 3 of the License or (at your option) any later
// version.
// (see http://www.opensource.org/licenses for more info)





void
group_classes
  (
  const ivec& labels,
  int* nr_class_ret,
  int** label_ret,
  int** start_ret,
  int** count_ret,
  int* perm
  )
  {
  int l = labels.n_rows;
  int max_nr_class = 16;
  int nr_class = 0;
  int* label = Malloc(int, max_nr_class);
  int* count = Malloc(int, max_nr_class);
  int* data_label = Malloc(int, l);
  int i;

  for(i = 0; i < l; i++)
    {
    int this_label = (int) labels[i];

    int j;
    for(j = 0; j < nr_class; j++)
      {
      if(this_label == label[j])
        {
        ++count[j];
        break;
        }
      }

    data_label[i] = j;
    if(j == nr_class)
      {
      if(nr_class == max_nr_class)
        {
        max_nr_class *= 2;
        label = (int*) realloc(label, max_nr_class * sizeof(int));
        count = (int*) realloc(count, max_nr_class * sizeof(int));
        }

      label[nr_class] = this_label;
      count[nr_class] = 1;
      ++nr_class;
      }
    }

  int* start = Malloc(int, nr_class);

  start[0] = 0;
  for(i = 1; i < nr_class; i++)
    {
    start[i] = start[i - 1] + count[i - 1];
    }

  for(i = 0; i < l; i++)
    {
    perm[start[data_label[i]]] = i;
    ++start[data_label[i]];
    }

  start[0] = 0;
  for(i = 1; i < nr_class; i++)
    {
    start[i] = start[i - 1] + count[i - 1];
    }

  *nr_class_ret = nr_class;
  *label_ret = label;
  *start_ret = start;
  *count_ret = count;
  free(data_label);
  }