/**
* Retrieves the neuron at location {@code (i, j)} in the map. The neuron at position {@code (0,
* 0)} is located at the upper-left corner of the map.
*
* @param i Row index.
* @param j Column index.
* @return the neuron at {@code (i, j)}.
* @throws OutOfRangeException if {@code i} or {@code j} is out of range.
* @see #getNeuron(int,int,HorizontalDirection,VerticalDirection)
*/
public Neuron getNeuron(int i, int j) {
if (i < 0 || i >= numberOfRows) {
throw new OutOfRangeException(i, 0, numberOfRows - 1);
}
if (j < 0 || j >= numberOfColumns) {
throw new OutOfRangeException(j, 0, numberOfColumns - 1);
}
return network.getNeuron(identifiers[i][j]);
}
/** Creates the neighbour relationships between neurons. */
private void createLinks() {
// "linkEnd" will store the identifiers of the "neighbours".
final List<Long> linkEnd = new ArrayList<Long>();
final int iLast = numberOfRows - 1;
final int jLast = numberOfColumns - 1;
for (int i = 0; i < numberOfRows; i++) {
for (int j = 0; j < numberOfColumns; j++) {
linkEnd.clear();
switch (neighbourhood) {
case MOORE:
// Add links to "diagonal" neighbours.
if (i > 0) {
if (j > 0) {
linkEnd.add(identifiers[i - 1][j - 1]);
}
if (j < jLast) {
linkEnd.add(identifiers[i - 1][j + 1]);
}
}
if (i < iLast) {
if (j > 0) {
linkEnd.add(identifiers[i + 1][j - 1]);
}
if (j < jLast) {
linkEnd.add(identifiers[i + 1][j + 1]);
}
}
if (wrapRows) {
if (i == 0) {
if (j > 0) {
linkEnd.add(identifiers[iLast][j - 1]);
}
if (j < jLast) {
linkEnd.add(identifiers[iLast][j + 1]);
}
} else if (i == iLast) {
if (j > 0) {
linkEnd.add(identifiers[0][j - 1]);
}
if (j < jLast) {
linkEnd.add(identifiers[0][j + 1]);
}
}
}
if (wrapColumns) {
if (j == 0) {
if (i > 0) {
linkEnd.add(identifiers[i - 1][jLast]);
}
if (i < iLast) {
linkEnd.add(identifiers[i + 1][jLast]);
}
} else if (j == jLast) {
if (i > 0) {
linkEnd.add(identifiers[i - 1][0]);
}
if (i < iLast) {
linkEnd.add(identifiers[i + 1][0]);
}
}
}
if (wrapRows && wrapColumns) {
if (i == 0 && j == 0) {
linkEnd.add(identifiers[iLast][jLast]);
} else if (i == 0 && j == jLast) {
linkEnd.add(identifiers[iLast][0]);
} else if (i == iLast && j == 0) {
linkEnd.add(identifiers[0][jLast]);
} else if (i == iLast && j == jLast) {
linkEnd.add(identifiers[0][0]);
}
}
// Case falls through since the "Moore" neighbourhood
// also contains the neurons that belong to the "Von
// Neumann" neighbourhood.
// fallthru (CheckStyle)
case VON_NEUMANN:
// Links to preceding and following "row".
if (i > 0) {
linkEnd.add(identifiers[i - 1][j]);
}
if (i < iLast) {
linkEnd.add(identifiers[i + 1][j]);
}
if (wrapRows) {
if (i == 0) {
linkEnd.add(identifiers[iLast][j]);
} else if (i == iLast) {
linkEnd.add(identifiers[0][j]);
}
}
// Links to preceding and following "column".
if (j > 0) {
linkEnd.add(identifiers[i][j - 1]);
}
if (j < jLast) {
linkEnd.add(identifiers[i][j + 1]);
}
if (wrapColumns) {
if (j == 0) {
linkEnd.add(identifiers[i][jLast]);
} else if (j == jLast) {
linkEnd.add(identifiers[i][0]);
}
}
break;
default:
throw new MathInternalError(); // Cannot happen.
}
final Neuron aNeuron = network.getNeuron(identifiers[i][j]);
for (long b : linkEnd) {
final Neuron bNeuron = network.getNeuron(b);
// Link to all neighbours.
// The reverse links will be added as the loop proceeds.
network.addLink(aNeuron, bNeuron);
}
}
}
}
