| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you under the Apache License, Version 2.0 (the |
| // "License"); you may not use this file except in compliance |
| // with the License. You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, |
| // software distributed under the License is distributed on an |
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| // KIND, either express or implied. See the License for the |
| // specific language governing permissions and limitations |
| // under the License. |
| |
| package org.spaceroots.mantissa.linalg; |
| |
| /** This class implements diagonal matrices of linear algebra. |
| |
| * @version $Id$ |
| * @author L. Maisonobe |
| |
| */ |
| |
| public class DiagonalMatrix |
| extends SquareMatrix { |
| |
| /** Simple constructor. |
| * This constructor builds a diagonal matrix of specified order, all |
| * elements on the diagonal being ones (so this is an identity matrix). |
| * @param order order of the matrix |
| */ |
| public DiagonalMatrix(int order) { |
| this(order, 1.0); |
| } |
| |
| /** Simple constructor. |
| * This constructor builds a diagonal matrix of specified order and |
| * set all diagonal elements to the same value. |
| * @param order order of the matrix |
| * @param value value for the diagonal elements |
| */ |
| public DiagonalMatrix(int order, double value) { |
| super(order); |
| for (int index = 0; index < order * order; index += order + 1) { |
| data[index] = value; |
| } |
| } |
| |
| /** Simple constructor. |
| * Build a matrix with specified elements. |
| * @param order order of the matrix |
| * @param data table of the matrix elements (stored row after row) |
| */ |
| public DiagonalMatrix(int order, double[] data) { |
| super(order, data); |
| } |
| |
| /** Copy constructor. |
| * @param d diagonal matrix to copy |
| */ |
| public DiagonalMatrix(DiagonalMatrix d) { |
| super(d); |
| } |
| |
| public Matrix duplicate() { |
| return new DiagonalMatrix(this); |
| } |
| |
| public void setElement(int i, int j, double value) { |
| if (i != j) { |
| throw new ArrayIndexOutOfBoundsException("cannot set elements" |
| + " out of diagonal in a" |
| + " diagonal matrix"); |
| } |
| super.setElement(i, j, value); |
| } |
| |
| public double getDeterminant(double epsilon) { |
| double determinant = data[0]; |
| for (int index = columns + 1; index < columns * columns; index += columns + 1) { |
| determinant *= data[index]; |
| } |
| return determinant; |
| } |
| |
| public SquareMatrix getInverse(double epsilon) |
| throws SingularMatrixException { |
| |
| DiagonalMatrix inv = new DiagonalMatrix (columns); |
| |
| for (int index = 0; index < columns * columns; index += columns + 1) { |
| if (Math.abs(data[index]) < epsilon) { |
| throw new SingularMatrixException(); |
| } |
| inv.data[index] = 1.0 / data[index]; |
| } |
| |
| return inv; |
| |
| } |
| |
| public Matrix solve(Matrix b, double epsilon) |
| throws SingularMatrixException { |
| |
| Matrix result = b.duplicate(); |
| |
| for (int i = 0; i < columns; ++i) { |
| double diag = data[i * (columns + 1)]; |
| if (Math.abs(diag) < epsilon) { |
| throw new SingularMatrixException(); |
| } |
| double inv = 1.0 / diag; |
| |
| NonNullRange range = result.getRangeForRow(i); |
| for (int index = i * b.columns + range.begin; |
| index < i * b.columns + range.end; |
| ++index) { |
| result.data[index] = inv * b.data[index]; |
| } |
| } |
| |
| return result; |
| |
| } |
| |
| public NonNullRange getRangeForRow(int i) { |
| return new NonNullRange(i, i + 1); |
| } |
| |
| public NonNullRange getRangeForColumn(int j) { |
| return new NonNullRange(j, j + 1); |
| } |
| |
| private static final long serialVersionUID = -2965166085913895323L; |
| |
| } |