1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.commons.math4.neuralnet.twod.util;
19
20 import java.util.Map;
21 import java.util.concurrent.ConcurrentHashMap;
22 import org.apache.commons.math4.neuralnet.Neuron;
23 import org.apache.commons.math4.neuralnet.twod.NeuronSquareMesh2D;
24
25 /**
26 * Helper class to find the grid coordinates of a neuron.
27 * @since 3.6
28 */
29 public class LocationFinder {
30 /** Identifier to location mapping. */
31 private final Map<Long, Location> locations = new ConcurrentHashMap<>();
32
33 /**
34 * Container holding a (row, column) pair.
35 */
36 public static class Location {
37 /** Row index. */
38 private final int row;
39 /** Column index. */
40 private final int column;
41
42 /**
43 * @param row Row index.
44 * @param column Column index.
45 */
46 public Location(int row,
47 int column) {
48 this.row = row;
49 this.column = column;
50 }
51
52 /**
53 * @return the row index.
54 */
55 public int getRow() {
56 return row;
57 }
58
59 /**
60 * @return the column index.
61 */
62 public int getColumn() {
63 return column;
64 }
65 }
66
67 /**
68 * Builds a finder to retrieve the locations of neurons that
69 * belong to the given {@code map}.
70 *
71 * @param map Map.
72 *
73 * @throws IllegalStateException if the network contains non-unique
74 * identifiers. This indicates an inconsistent state due to a bug in
75 * the construction code of the underlying
76 * {@link org.apache.commons.math4.neuralnet.Network network}.
77 */
78 public LocationFinder(NeuronSquareMesh2D map) {
79 final int nR = map.getNumberOfRows();
80 final int nC = map.getNumberOfColumns();
81
82 for (int r = 0; r < nR; r++) {
83 for (int c = 0; c < nC; c++) {
84 final Long id = map.getNeuron(r, c).getIdentifier();
85 if (locations.get(id) != null) {
86 throw new IllegalStateException();
87 }
88 locations.put(id, new Location(r, c));
89 }
90 }
91 }
92
93 /**
94 * Retrieves a neuron's grid coordinates.
95 *
96 * @param n Neuron.
97 * @return the (row, column) coordinates of {@code n}, or {@code null}
98 * if no such neuron belongs to the {@link #LocationFinder(NeuronSquareMesh2D)
99 * map used to build this instance}.
100 */
101 public Location getLocation(Neuron n) {
102 return locations.get(n.getIdentifier());
103 }
104 }