Alexandria  2.27.0
SDC-CH common library for the Euclid project
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NeihbourhoodFunc.cpp
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1 /*
2  * Copyright (C) 2012-2022 Euclid Science Ground Segment
3  *
4  * This library is free software; you can redistribute it and/or modify it under
5  * the terms of the GNU Lesser General Public License as published by the Free
6  * Software Foundation; either version 3.0 of the License, or (at your option)
7  * any later version.
8  *
9  * This library is distributed in the hope that it will be useful, but WITHOUT
10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
11  * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
12  * details.
13  *
14  * You should have received a copy of the GNU Lesser General Public License
15  * along with this library; if not, write to the Free Software Foundation, Inc.,
16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 #include "SOM/NeighborhoodFunc.h"
20 #include <algorithm> // std::max
21 #include <cmath>
22 
23 namespace Euclid {
24 namespace SOM {
25 namespace NeighborhoodFunc {
26 
28  std::size_t iteration, std::size_t total_iterations) {
29  double iter_factor = 1.0 * static_cast<double>(total_iterations - iteration) / static_cast<double>(total_iterations);
30  iter_factor = iter_factor * iter_factor; // We compare the squared distances
31  auto x = static_cast<double>(bmu.first - cell.first);
32  auto y = static_cast<double>(bmu.second - cell.second);
33  double dist_square = x * x + y * y;
34  if (dist_square < m_r_square * iter_factor) {
35  return 1.;
36  } else {
37  return 0.;
38  }
39 }
40 
41 Kohonen::Kohonen(std::size_t x_size, std::size_t y_size, double sigma_cutoff_mult)
42  : m_init_sigma(static_cast<double>(std::max(x_size, y_size)) / 2.)
43  , m_sigma_log(std::log(m_init_sigma))
44  , m_cutoff_mult_square{sigma_cutoff_mult * sigma_cutoff_mult} {}
45 
46 } // namespace NeighborhoodFunc
47 } // namespace SOM
48 } // namespace Euclid
double operator()(std::pair< std::size_t, std::size_t > bmu, std::pair< std::size_t, std::size_t > cell, std::size_t iteration, std::size_t total_iterations)
auto log
Kohonen(std::size_t x_size, std::size_t y_size, double sigma_cutoff_mult)