Java tutorial
/* * 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.apache.commons.math3.linear; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.lang.reflect.Array; import java.util.Arrays; import org.apache.commons.math3.Field; import org.apache.commons.math3.FieldElement; import org.apache.commons.math3.exception.MathArithmeticException; import org.apache.commons.math3.exception.OutOfRangeException; import org.apache.commons.math3.exception.NoDataException; import org.apache.commons.math3.exception.NumberIsTooSmallException; import org.apache.commons.math3.exception.NullArgumentException; import org.apache.commons.math3.exception.DimensionMismatchException; import org.apache.commons.math3.exception.ZeroException; import org.apache.commons.math3.exception.util.LocalizedFormats; import org.apache.commons.math3.fraction.BigFraction; import org.apache.commons.math3.fraction.Fraction; import org.apache.commons.math3.util.FastMath; import org.apache.commons.math3.util.Precision; /** * A collection of static methods that operate on or return matrices. * * @version $Id: MatrixUtils.java 1422313 2012-12-15 18:53:41Z psteitz $ */ public class MatrixUtils { /** * The default format for {@link RealMatrix} objects. * @since 3.1 */ public static final RealMatrixFormat DEFAULT_FORMAT = RealMatrixFormat.getInstance(); /** * A format for {@link RealMatrix} objects compatible with octave. * @since 3.1 */ public static final RealMatrixFormat OCTAVE_FORMAT = new RealMatrixFormat("[", "]", "", "", "; ", ", "); /** * Private constructor. */ private MatrixUtils() { super(); } /** * Returns a {@link RealMatrix} with specified dimensions. * <p>The type of matrix returned depends on the dimension. Below * 2<sup>12</sup> elements (i.e. 4096 elements or 64×64 for a * square matrix) which can be stored in a 32kB array, a {@link * Array2DRowRealMatrix} instance is built. Above this threshold a {@link * BlockRealMatrix} instance is built.</p> * <p>The matrix elements are all set to 0.0.</p> * @param rows number of rows of the matrix * @param columns number of columns of the matrix * @return RealMatrix with specified dimensions * @see #createRealMatrix(double[][]) */ public static RealMatrix createRealMatrix(final int rows, final int columns) { return (rows * columns <= 4096) ? new Array2DRowRealMatrix(rows, columns) : new BlockRealMatrix(rows, columns); } /** * Returns a {@link FieldMatrix} with specified dimensions. * <p>The type of matrix returned depends on the dimension. Below * 2<sup>12</sup> elements (i.e. 4096 elements or 64×64 for a * square matrix), a {@link FieldMatrix} instance is built. Above * this threshold a {@link BlockFieldMatrix} instance is built.</p> * <p>The matrix elements are all set to field.getZero().</p> * @param <T> the type of the field elements * @param field field to which the matrix elements belong * @param rows number of rows of the matrix * @param columns number of columns of the matrix * @return FieldMatrix with specified dimensions * @see #createFieldMatrix(FieldElement[][]) * @since 2.0 */ public static <T extends FieldElement<T>> FieldMatrix<T> createFieldMatrix(final Field<T> field, final int rows, final int columns) { return (rows * columns <= 4096) ? new Array2DRowFieldMatrix<T>(field, rows, columns) : new BlockFieldMatrix<T>(field, rows, columns); } /** * Returns a {@link RealMatrix} whose entries are the the values in the * the input array. * <p>The type of matrix returned depends on the dimension. Below * 2<sup>12</sup> elements (i.e. 4096 elements or 64×64 for a * square matrix) which can be stored in a 32kB array, a {@link * Array2DRowRealMatrix} instance is built. Above this threshold a {@link * BlockRealMatrix} instance is built.</p> * <p>The input array is copied, not referenced.</p> * * @param data input array * @return RealMatrix containing the values of the array * @throws org.apache.commons.math3.exception.DimensionMismatchException * if {@code data} is not rectangular (not all rows have the same length). * @throws NoDataException if a row or column is empty. * @throws NullArgumentException if either {@code data} or {@code data[0]} * is {@code null}. * @throws DimensionMismatchException if {@code data} is not rectangular. * @see #createRealMatrix(int, int) */ public static RealMatrix createRealMatrix(double[][] data) throws NullArgumentException, DimensionMismatchException, NoDataException { if (data == null || data[0] == null) { throw new NullArgumentException(); } return (data.length * data[0].length <= 4096) ? new Array2DRowRealMatrix(data) : new BlockRealMatrix(data); } /** * Returns a {@link FieldMatrix} whose entries are the the values in the * the input array. * <p>The type of matrix returned depends on the dimension. Below * 2<sup>12</sup> elements (i.e. 4096 elements or 64×64 for a * square matrix), a {@link FieldMatrix} instance is built. Above * this threshold a {@link BlockFieldMatrix} instance is built.</p> * <p>The input array is copied, not referenced.</p> * @param <T> the type of the field elements * @param data input array * @return a matrix containing the values of the array. * @throws org.apache.commons.math3.exception.DimensionMismatchException * if {@code data} is not rectangular (not all rows have the same length). * @throws NoDataException if a row or column is empty. * @throws NullArgumentException if either {@code data} or {@code data[0]} * is {@code null}. * @see #createFieldMatrix(Field, int, int) * @since 2.0 */ public static <T extends FieldElement<T>> FieldMatrix<T> createFieldMatrix(T[][] data) throws DimensionMismatchException, NoDataException, NullArgumentException { if (data == null || data[0] == null) { throw new NullArgumentException(); } return (data.length * data[0].length <= 4096) ? new Array2DRowFieldMatrix<T>(data) : new BlockFieldMatrix<T>(data); } /** * Returns <code>dimension x dimension</code> identity matrix. * * @param dimension dimension of identity matrix to generate * @return identity matrix * @throws IllegalArgumentException if dimension is not positive * @since 1.1 */ public static RealMatrix createRealIdentityMatrix(int dimension) { final RealMatrix m = createRealMatrix(dimension, dimension); for (int i = 0; i < dimension; ++i) { m.setEntry(i, i, 1.0); } return m; } /** * Returns <code>dimension x dimension</code> identity matrix. * * @param <T> the type of the field elements * @param field field to which the elements belong * @param dimension dimension of identity matrix to generate * @return identity matrix * @throws IllegalArgumentException if dimension is not positive * @since 2.0 */ public static <T extends FieldElement<T>> FieldMatrix<T> createFieldIdentityMatrix(final Field<T> field, final int dimension) { final T zero = field.getZero(); final T one = field.getOne(); @SuppressWarnings("unchecked") final T[][] d = (T[][]) Array.newInstance(field.getRuntimeClass(), new int[] { dimension, dimension }); for (int row = 0; row < dimension; row++) { final T[] dRow = d[row]; Arrays.fill(dRow, zero); dRow[row] = one; } return new Array2DRowFieldMatrix<T>(field, d, false); } /** * Returns a diagonal matrix with specified elements. * * @param diagonal diagonal elements of the matrix (the array elements * will be copied) * @return diagonal matrix * @since 2.0 */ public static RealMatrix createRealDiagonalMatrix(final double[] diagonal) { final RealMatrix m = createRealMatrix(diagonal.length, diagonal.length); for (int i = 0; i < diagonal.length; ++i) { m.setEntry(i, i, diagonal[i]); } return m; } /** * Returns a diagonal matrix with specified elements. * * @param <T> the type of the field elements * @param diagonal diagonal elements of the matrix (the array elements * will be copied) * @return diagonal matrix * @since 2.0 */ public static <T extends FieldElement<T>> FieldMatrix<T> createFieldDiagonalMatrix(final T[] diagonal) { final FieldMatrix<T> m = createFieldMatrix(diagonal[0].getField(), diagonal.length, diagonal.length); for (int i = 0; i < diagonal.length; ++i) { m.setEntry(i, i, diagonal[i]); } return m; } /** * Creates a {@link RealVector} using the data from the input array. * * @param data the input data * @return a data.length RealVector * @throws NoDataException if {@code data} is empty. * @throws NullArgumentException if {@code data} is {@code null}. */ public static RealVector createRealVector(double[] data) throws NoDataException, NullArgumentException { if (data == null) { throw new NullArgumentException(); } return new ArrayRealVector(data, true); } /** * Creates a {@link FieldVector} using the data from the input array. * * @param <T> the type of the field elements * @param data the input data * @return a data.length FieldVector * @throws NoDataException if {@code data} is empty. * @throws NullArgumentException if {@code data} is {@code null}. * @throws ZeroException if {@code data} has 0 elements */ public static <T extends FieldElement<T>> FieldVector<T> createFieldVector(final T[] data) throws NoDataException, NullArgumentException, ZeroException { if (data == null) { throw new NullArgumentException(); } if (data.length == 0) { throw new ZeroException(LocalizedFormats.VECTOR_MUST_HAVE_AT_LEAST_ONE_ELEMENT); } return new ArrayFieldVector<T>(data[0].getField(), data, true); } /** * Create a row {@link RealMatrix} using the data from the input * array. * * @param rowData the input row data * @return a 1 x rowData.length RealMatrix * @throws NoDataException if {@code rowData} is empty. * @throws NullArgumentException if {@code rowData} is {@code null}. */ public static RealMatrix createRowRealMatrix(double[] rowData) throws NoDataException, NullArgumentException { if (rowData == null) { throw new NullArgumentException(); } final int nCols = rowData.length; final RealMatrix m = createRealMatrix(1, nCols); for (int i = 0; i < nCols; ++i) { m.setEntry(0, i, rowData[i]); } return m; } /** * Create a row {@link FieldMatrix} using the data from the input * array. * * @param <T> the type of the field elements * @param rowData the input row data * @return a 1 x rowData.length FieldMatrix * @throws NoDataException if {@code rowData} is empty. * @throws NullArgumentException if {@code rowData} is {@code null}. */ public static <T extends FieldElement<T>> FieldMatrix<T> createRowFieldMatrix(final T[] rowData) throws NoDataException, NullArgumentException { if (rowData == null) { throw new NullArgumentException(); } final int nCols = rowData.length; if (nCols == 0) { throw new NoDataException(LocalizedFormats.AT_LEAST_ONE_COLUMN); } final FieldMatrix<T> m = createFieldMatrix(rowData[0].getField(), 1, nCols); for (int i = 0; i < nCols; ++i) { m.setEntry(0, i, rowData[i]); } return m; } /** * Creates a column {@link RealMatrix} using the data from the input * array. * * @param columnData the input column data * @return a columnData x 1 RealMatrix * @throws NoDataException if {@code columnData} is empty. * @throws NullArgumentException if {@code columnData} is {@code null}. */ public static RealMatrix createColumnRealMatrix(double[] columnData) throws NoDataException, NullArgumentException { if (columnData == null) { throw new NullArgumentException(); } final int nRows = columnData.length; final RealMatrix m = createRealMatrix(nRows, 1); for (int i = 0; i < nRows; ++i) { m.setEntry(i, 0, columnData[i]); } return m; } /** * Creates a column {@link FieldMatrix} using the data from the input * array. * * @param <T> the type of the field elements * @param columnData the input column data * @return a columnData x 1 FieldMatrix * @throws NoDataException if {@code data} is empty. * @throws NullArgumentException if {@code columnData} is {@code null}. */ public static <T extends FieldElement<T>> FieldMatrix<T> createColumnFieldMatrix(final T[] columnData) throws NoDataException, NullArgumentException { if (columnData == null) { throw new NullArgumentException(); } final int nRows = columnData.length; if (nRows == 0) { throw new NoDataException(LocalizedFormats.AT_LEAST_ONE_ROW); } final FieldMatrix<T> m = createFieldMatrix(columnData[0].getField(), nRows, 1); for (int i = 0; i < nRows; ++i) { m.setEntry(i, 0, columnData[i]); } return m; } /** * Checks whether a matrix is symmetric, within a given relative tolerance. * * @param matrix Matrix to check. * @param relativeTolerance Tolerance of the symmetry check. * @param raiseException If {@code true}, an exception will be raised if * the matrix is not symmetric. * @return {@code true} if {@code matrix} is symmetric. * @throws NonSquareMatrixException if the matrix is not square. * @throws NonSymmetricMatrixException if the matrix is not symmetric. */ private static boolean isSymmetricInternal(RealMatrix matrix, double relativeTolerance, boolean raiseException) { final int rows = matrix.getRowDimension(); if (rows != matrix.getColumnDimension()) { if (raiseException) { throw new NonSquareMatrixException(rows, matrix.getColumnDimension()); } else { return false; } } for (int i = 0; i < rows; i++) { for (int j = i + 1; j < rows; j++) { final double mij = matrix.getEntry(i, j); final double mji = matrix.getEntry(j, i); if (FastMath.abs(mij - mji) > FastMath.max(FastMath.abs(mij), FastMath.abs(mji)) * relativeTolerance) { if (raiseException) { throw new NonSymmetricMatrixException(i, j, relativeTolerance); } else { return false; } } } } return true; } /** * Checks whether a matrix is symmetric. * * @param matrix Matrix to check. * @param eps Relative tolerance. * @throws NonSquareMatrixException if the matrix is not square. * @throws NonSymmetricMatrixException if the matrix is not symmetric. * @since 3.1 */ public static void checkSymmetric(RealMatrix matrix, double eps) { isSymmetricInternal(matrix, eps, true); } /** * Checks whether a matrix is symmetric. * * @param matrix Matrix to check. * @param eps Relative tolerance. * @return {@code true} if {@code matrix} is symmetric. * @since 3.1 */ public static boolean isSymmetric(RealMatrix matrix, double eps) { return isSymmetricInternal(matrix, eps, false); } /** * Check if matrix indices are valid. * * @param m Matrix. * @param row Row index to check. * @param column Column index to check. * @throws OutOfRangeException if {@code row} or {@code column} is not * a valid index. */ public static void checkMatrixIndex(final AnyMatrix m, final int row, final int column) throws OutOfRangeException { checkRowIndex(m, row); checkColumnIndex(m, column); } /** * Check if a row index is valid. * * @param m Matrix. * @param row Row index to check. * @throws OutOfRangeException if {@code row} is not a valid index. */ public static void checkRowIndex(final AnyMatrix m, final int row) throws OutOfRangeException { if (row < 0 || row >= m.getRowDimension()) { throw new OutOfRangeException(LocalizedFormats.ROW_INDEX, row, 0, m.getRowDimension() - 1); } } /** * Check if a column index is valid. * * @param m Matrix. * @param column Column index to check. * @throws OutOfRangeException if {@code column} is not a valid index. */ public static void checkColumnIndex(final AnyMatrix m, final int column) throws OutOfRangeException { if (column < 0 || column >= m.getColumnDimension()) { throw new OutOfRangeException(LocalizedFormats.COLUMN_INDEX, column, 0, m.getColumnDimension() - 1); } } /** * Check if submatrix ranges indices are valid. * Rows and columns are indicated counting from 0 to {@code n - 1}. * * @param m Matrix. * @param startRow Initial row index. * @param endRow Final row index. * @param startColumn Initial column index. * @param endColumn Final column index. * @throws OutOfRangeException if the indices are invalid. * @throws NumberIsTooSmallException if {@code endRow < startRow} or * {@code endColumn < startColumn}. */ public static void checkSubMatrixIndex(final AnyMatrix m, final int startRow, final int endRow, final int startColumn, final int endColumn) throws NumberIsTooSmallException, OutOfRangeException { checkRowIndex(m, startRow); checkRowIndex(m, endRow); if (endRow < startRow) { throw new NumberIsTooSmallException(LocalizedFormats.INITIAL_ROW_AFTER_FINAL_ROW, endRow, startRow, false); } checkColumnIndex(m, startColumn); checkColumnIndex(m, endColumn); if (endColumn < startColumn) { throw new NumberIsTooSmallException(LocalizedFormats.INITIAL_COLUMN_AFTER_FINAL_COLUMN, endColumn, startColumn, false); } } /** * Check if submatrix ranges indices are valid. * Rows and columns are indicated counting from 0 to n-1. * * @param m Matrix. * @param selectedRows Array of row indices. * @param selectedColumns Array of column indices. * @throws NullArgumentException if {@code selectedRows} or * {@code selectedColumns} are {@code null}. * @throws NoDataException if the row or column selections are empty (zero * length). * @throws OutOfRangeException if row or column selections are not valid. */ public static void checkSubMatrixIndex(final AnyMatrix m, final int[] selectedRows, final int[] selectedColumns) throws NoDataException, NullArgumentException, OutOfRangeException { if (selectedRows == null) { throw new NullArgumentException(); } if (selectedColumns == null) { throw new NullArgumentException(); } if (selectedRows.length == 0) { throw new NoDataException(LocalizedFormats.EMPTY_SELECTED_ROW_INDEX_ARRAY); } if (selectedColumns.length == 0) { throw new NoDataException(LocalizedFormats.EMPTY_SELECTED_COLUMN_INDEX_ARRAY); } for (final int row : selectedRows) { checkRowIndex(m, row); } for (final int column : selectedColumns) { checkColumnIndex(m, column); } } /** * Check if matrices are addition compatible. * * @param left Left hand side matrix. * @param right Right hand side matrix. * @throws MatrixDimensionMismatchException if the matrices are not addition * compatible. */ public static void checkAdditionCompatible(final AnyMatrix left, final AnyMatrix right) throws MatrixDimensionMismatchException { if ((left.getRowDimension() != right.getRowDimension()) || (left.getColumnDimension() != right.getColumnDimension())) { throw new MatrixDimensionMismatchException(left.getRowDimension(), left.getColumnDimension(), right.getRowDimension(), right.getColumnDimension()); } } /** * Check if matrices are subtraction compatible * * @param left Left hand side matrix. * @param right Right hand side matrix. * @throws MatrixDimensionMismatchException if the matrices are not addition * compatible. */ public static void checkSubtractionCompatible(final AnyMatrix left, final AnyMatrix right) throws MatrixDimensionMismatchException { if ((left.getRowDimension() != right.getRowDimension()) || (left.getColumnDimension() != right.getColumnDimension())) { throw new MatrixDimensionMismatchException(left.getRowDimension(), left.getColumnDimension(), right.getRowDimension(), right.getColumnDimension()); } } /** * Check if matrices are multiplication compatible * * @param left Left hand side matrix. * @param right Right hand side matrix. * @throws DimensionMismatchException if matrices are not multiplication * compatible. */ public static void checkMultiplicationCompatible(final AnyMatrix left, final AnyMatrix right) throws DimensionMismatchException { if (left.getColumnDimension() != right.getRowDimension()) { throw new DimensionMismatchException(left.getColumnDimension(), right.getRowDimension()); } } /** * Convert a {@link FieldMatrix}/{@link Fraction} matrix to a {@link RealMatrix}. * @param m Matrix to convert. * @return the converted matrix. */ public static Array2DRowRealMatrix fractionMatrixToRealMatrix(final FieldMatrix<Fraction> m) { final FractionMatrixConverter converter = new FractionMatrixConverter(); m.walkInOptimizedOrder(converter); return converter.getConvertedMatrix(); } /** Converter for {@link FieldMatrix}/{@link Fraction}. */ private static class FractionMatrixConverter extends DefaultFieldMatrixPreservingVisitor<Fraction> { /** Converted array. */ private double[][] data; /** Simple constructor. */ public FractionMatrixConverter() { super(Fraction.ZERO); } /** {@inheritDoc} */ @Override public void start(int rows, int columns, int startRow, int endRow, int startColumn, int endColumn) { data = new double[rows][columns]; } /** {@inheritDoc} */ @Override public void visit(int row, int column, Fraction value) { data[row][column] = value.doubleValue(); } /** * Get the converted matrix. * * @return the converted matrix. */ Array2DRowRealMatrix getConvertedMatrix() { return new Array2DRowRealMatrix(data, false); } } /** * Convert a {@link FieldMatrix}/{@link BigFraction} matrix to a {@link RealMatrix}. * * @param m Matrix to convert. * @return the converted matrix. */ public static Array2DRowRealMatrix bigFractionMatrixToRealMatrix(final FieldMatrix<BigFraction> m) { final BigFractionMatrixConverter converter = new BigFractionMatrixConverter(); m.walkInOptimizedOrder(converter); return converter.getConvertedMatrix(); } /** Converter for {@link FieldMatrix}/{@link BigFraction}. */ private static class BigFractionMatrixConverter extends DefaultFieldMatrixPreservingVisitor<BigFraction> { /** Converted array. */ private double[][] data; /** Simple constructor. */ public BigFractionMatrixConverter() { super(BigFraction.ZERO); } /** {@inheritDoc} */ @Override public void start(int rows, int columns, int startRow, int endRow, int startColumn, int endColumn) { data = new double[rows][columns]; } /** {@inheritDoc} */ @Override public void visit(int row, int column, BigFraction value) { data[row][column] = value.doubleValue(); } /** * Get the converted matrix. * * @return the converted matrix. */ Array2DRowRealMatrix getConvertedMatrix() { return new Array2DRowRealMatrix(data, false); } } /** Serialize a {@link RealVector}. * <p> * This method is intended to be called from within a private * <code>writeObject</code> method (after a call to * <code>oos.defaultWriteObject()</code>) in a class that has a * {@link RealVector} field, which should be declared <code>transient</code>. * This way, the default handling does not serialize the vector (the {@link * RealVector} interface is not serializable by default) but this method does * serialize it specifically. * </p> * <p> * The following example shows how a simple class with a name and a real vector * should be written: * <pre><code> * public class NamedVector implements Serializable { * * private final String name; * private final transient RealVector coefficients; * * // omitted constructors, getters ... * * private void writeObject(ObjectOutputStream oos) throws IOException { * oos.defaultWriteObject(); // takes care of name field * MatrixUtils.serializeRealVector(coefficients, oos); * } * * private void readObject(ObjectInputStream ois) throws ClassNotFoundException, IOException { * ois.defaultReadObject(); // takes care of name field * MatrixUtils.deserializeRealVector(this, "coefficients", ois); * } * * } * </code></pre> * </p> * * @param vector real vector to serialize * @param oos stream where the real vector should be written * @exception IOException if object cannot be written to stream * @see #deserializeRealVector(Object, String, ObjectInputStream) */ public static void serializeRealVector(final RealVector vector, final ObjectOutputStream oos) throws IOException { final int n = vector.getDimension(); oos.writeInt(n); for (int i = 0; i < n; ++i) { oos.writeDouble(vector.getEntry(i)); } } /** Deserialize a {@link RealVector} field in a class. * <p> * This method is intended to be called from within a private * <code>readObject</code> method (after a call to * <code>ois.defaultReadObject()</code>) in a class that has a * {@link RealVector} field, which should be declared <code>transient</code>. * This way, the default handling does not deserialize the vector (the {@link * RealVector} interface is not serializable by default) but this method does * deserialize it specifically. * </p> * @param instance instance in which the field must be set up * @param fieldName name of the field within the class (may be private and final) * @param ois stream from which the real vector should be read * @exception ClassNotFoundException if a class in the stream cannot be found * @exception IOException if object cannot be read from the stream * @see #serializeRealVector(RealVector, ObjectOutputStream) */ public static void deserializeRealVector(final Object instance, final String fieldName, final ObjectInputStream ois) throws ClassNotFoundException, IOException { try { // read the vector data final int n = ois.readInt(); final double[] data = new double[n]; for (int i = 0; i < n; ++i) { data[i] = ois.readDouble(); } // create the instance final RealVector vector = new ArrayRealVector(data, false); // set up the field final java.lang.reflect.Field f = instance.getClass().getDeclaredField(fieldName); f.setAccessible(true); f.set(instance, vector); } catch (NoSuchFieldException nsfe) { IOException ioe = new IOException(); ioe.initCause(nsfe); throw ioe; } catch (IllegalAccessException iae) { IOException ioe = new IOException(); ioe.initCause(iae); throw ioe; } } /** Serialize a {@link RealMatrix}. * <p> * This method is intended to be called from within a private * <code>writeObject</code> method (after a call to * <code>oos.defaultWriteObject()</code>) in a class that has a * {@link RealMatrix} field, which should be declared <code>transient</code>. * This way, the default handling does not serialize the matrix (the {@link * RealMatrix} interface is not serializable by default) but this method does * serialize it specifically. * </p> * <p> * The following example shows how a simple class with a name and a real matrix * should be written: * <pre><code> * public class NamedMatrix implements Serializable { * * private final String name; * private final transient RealMatrix coefficients; * * // omitted constructors, getters ... * * private void writeObject(ObjectOutputStream oos) throws IOException { * oos.defaultWriteObject(); // takes care of name field * MatrixUtils.serializeRealMatrix(coefficients, oos); * } * * private void readObject(ObjectInputStream ois) throws ClassNotFoundException, IOException { * ois.defaultReadObject(); // takes care of name field * MatrixUtils.deserializeRealMatrix(this, "coefficients", ois); * } * * } * </code></pre> * </p> * * @param matrix real matrix to serialize * @param oos stream where the real matrix should be written * @exception IOException if object cannot be written to stream * @see #deserializeRealMatrix(Object, String, ObjectInputStream) */ public static void serializeRealMatrix(final RealMatrix matrix, final ObjectOutputStream oos) throws IOException { final int n = matrix.getRowDimension(); final int m = matrix.getColumnDimension(); oos.writeInt(n); oos.writeInt(m); for (int i = 0; i < n; ++i) { for (int j = 0; j < m; ++j) { oos.writeDouble(matrix.getEntry(i, j)); } } } /** Deserialize a {@link RealMatrix} field in a class. * <p> * This method is intended to be called from within a private * <code>readObject</code> method (after a call to * <code>ois.defaultReadObject()</code>) in a class that has a * {@link RealMatrix} field, which should be declared <code>transient</code>. * This way, the default handling does not deserialize the matrix (the {@link * RealMatrix} interface is not serializable by default) but this method does * deserialize it specifically. * </p> * @param instance instance in which the field must be set up * @param fieldName name of the field within the class (may be private and final) * @param ois stream from which the real matrix should be read * @exception ClassNotFoundException if a class in the stream cannot be found * @exception IOException if object cannot be read from the stream * @see #serializeRealMatrix(RealMatrix, ObjectOutputStream) */ public static void deserializeRealMatrix(final Object instance, final String fieldName, final ObjectInputStream ois) throws ClassNotFoundException, IOException { try { // read the matrix data final int n = ois.readInt(); final int m = ois.readInt(); final double[][] data = new double[n][m]; for (int i = 0; i < n; ++i) { final double[] dataI = data[i]; for (int j = 0; j < m; ++j) { dataI[j] = ois.readDouble(); } } // create the instance final RealMatrix matrix = new Array2DRowRealMatrix(data, false); // set up the field final java.lang.reflect.Field f = instance.getClass().getDeclaredField(fieldName); f.setAccessible(true); f.set(instance, matrix); } catch (NoSuchFieldException nsfe) { IOException ioe = new IOException(); ioe.initCause(nsfe); throw ioe; } catch (IllegalAccessException iae) { IOException ioe = new IOException(); ioe.initCause(iae); throw ioe; } } /**Solve a system of composed of a Lower Triangular Matrix * {@link RealMatrix}. * <p> * This method is called to solve systems of equations which are * of the lower triangular form. The matrix {@link RealMatrix} * is assumed, though not checked, to be in lower triangular form. * The vector {@link RealVector} is overwritten with the solution. * The matrix is checked that it is square and its dimensions match * the length of the vector. * </p> * @param rm RealMatrix which is lower triangular * @param b RealVector this is overwritten * @throws DimensionMismatchException if the matrix and vector are not * conformable * @throws NonSquareMatrixException if the matrix {@code rm} is not square * @throws MathArithmeticException if the absolute value of one of the diagonal * coefficient of {@code rm} is lower than {@link Precision#SAFE_MIN} */ public static void solveLowerTriangularSystem(RealMatrix rm, RealVector b) throws DimensionMismatchException, MathArithmeticException, NonSquareMatrixException { if ((rm == null) || (b == null) || (rm.getRowDimension() != b.getDimension())) { throw new DimensionMismatchException((rm == null) ? 0 : rm.getRowDimension(), (b == null) ? 0 : b.getDimension()); } if (rm.getColumnDimension() != rm.getRowDimension()) { throw new NonSquareMatrixException(rm.getRowDimension(), rm.getColumnDimension()); } int rows = rm.getRowDimension(); for (int i = 0; i < rows; i++) { double diag = rm.getEntry(i, i); if (FastMath.abs(diag) < Precision.SAFE_MIN) { throw new MathArithmeticException(LocalizedFormats.ZERO_DENOMINATOR); } double bi = b.getEntry(i) / diag; b.setEntry(i, bi); for (int j = i + 1; j < rows; j++) { b.setEntry(j, b.getEntry(j) - bi * rm.getEntry(j, i)); } } } /** Solver a system composed of an Upper Triangular Matrix * {@link RealMatrix}. * <p> * This method is called to solve systems of equations which are * of the lower triangular form. The matrix {@link RealMatrix} * is assumed, though not checked, to be in upper triangular form. * The vector {@link RealVector} is overwritten with the solution. * The matrix is checked that it is square and its dimensions match * the length of the vector. * </p> * @param rm RealMatrix which is upper triangular * @param b RealVector this is overwritten * @throws DimensionMismatchException if the matrix and vector are not * conformable * @throws NonSquareMatrixException if the matrix {@code rm} is not * square * @throws MathArithmeticException if the absolute value of one of the diagonal * coefficient of {@code rm} is lower than {@link Precision#SAFE_MIN} */ public static void solveUpperTriangularSystem(RealMatrix rm, RealVector b) throws DimensionMismatchException, MathArithmeticException, NonSquareMatrixException { if ((rm == null) || (b == null) || (rm.getRowDimension() != b.getDimension())) { throw new DimensionMismatchException((rm == null) ? 0 : rm.getRowDimension(), (b == null) ? 0 : b.getDimension()); } if (rm.getColumnDimension() != rm.getRowDimension()) { throw new NonSquareMatrixException(rm.getRowDimension(), rm.getColumnDimension()); } int rows = rm.getRowDimension(); for (int i = rows - 1; i > -1; i--) { double diag = rm.getEntry(i, i); if (FastMath.abs(diag) < Precision.SAFE_MIN) { throw new MathArithmeticException(LocalizedFormats.ZERO_DENOMINATOR); } double bi = b.getEntry(i) / diag; b.setEntry(i, bi); for (int j = i - 1; j > -1; j--) { b.setEntry(j, b.getEntry(j) - bi * rm.getEntry(j, i)); } } } /** * Computes the inverse of the given matrix by splitting it into * 4 sub-matrices. * * @param m Matrix whose inverse must be computed. * @param splitIndex Index that determines the "split" line and * column. * The element corresponding to this index will part of the * upper-left sub-matrix. * @return the inverse of {@code m}. * @throws NonSquareMatrixException if {@code m} is not square. */ public static RealMatrix blockInverse(RealMatrix m, int splitIndex) { final int n = m.getRowDimension(); if (m.getColumnDimension() != n) { throw new NonSquareMatrixException(m.getRowDimension(), m.getColumnDimension()); } final int splitIndex1 = splitIndex + 1; final RealMatrix a = m.getSubMatrix(0, splitIndex, 0, splitIndex); final RealMatrix b = m.getSubMatrix(0, splitIndex, splitIndex1, n - 1); final RealMatrix c = m.getSubMatrix(splitIndex1, n - 1, 0, splitIndex); final RealMatrix d = m.getSubMatrix(splitIndex1, n - 1, splitIndex1, n - 1); final SingularValueDecomposition aDec = new SingularValueDecomposition(a); final RealMatrix aInv = aDec.getSolver().getInverse(); final SingularValueDecomposition dDec = new SingularValueDecomposition(d); final RealMatrix dInv = dDec.getSolver().getInverse(); final RealMatrix tmp1 = a.subtract(b.multiply(dInv).multiply(c)); final SingularValueDecomposition tmp1Dec = new SingularValueDecomposition(tmp1); final RealMatrix result00 = tmp1Dec.getSolver().getInverse(); final RealMatrix tmp2 = d.subtract(c.multiply(aInv).multiply(b)); final SingularValueDecomposition tmp2Dec = new SingularValueDecomposition(tmp2); final RealMatrix result11 = tmp2Dec.getSolver().getInverse(); final RealMatrix result01 = aInv.multiply(b).multiply(result11).scalarMultiply(-1); final RealMatrix result10 = dInv.multiply(c).multiply(result00).scalarMultiply(-1); final RealMatrix result = new Array2DRowRealMatrix(n, n); result.setSubMatrix(result00.getData(), 0, 0); result.setSubMatrix(result01.getData(), 0, splitIndex1); result.setSubMatrix(result10.getData(), splitIndex1, 0); result.setSubMatrix(result11.getData(), splitIndex1, splitIndex1); return result; } }