

Java example source code file (RealLinearOperator.java)
The RealLinearOperator.java Java example source code/* * 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/LICENSE2.0 * * 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 org.apache.commons.math3.exception.DimensionMismatchException; /** * This class defines a linear operator operating on real ({@code double}) * vector spaces. No direct access to the coefficients of the underlying matrix * is provided. * * The motivation for such an interface is well stated by * <a href="#BARR1994">Barrett et al. (1994): * <blockquote> * We restrict ourselves to iterative methods, which work by repeatedly * improving an approximate solution until it is accurate enough. These * methods access the coefficient matrix A of the linear system only via the * matrixvector product y = A · x * (and perhaps z = A<sup>T · x). Thus the user need only * supply a subroutine for computing y (and perhaps z) given x, which permits * full exploitation of the sparsity or other special structure of A. * </blockquote> * <br/> * * <dl> * <dt>Barret et al. (1994) * <dd> * R. Barrett, M. Berry, T. F. Chan, J. Demmel, J. M. Donato, J. Dongarra, * V. Eijkhout, R. Pozo, C. Romine and H. Van der Vorst, * <em>Templates for the Solution of Linear Systems: Building Blocks for * Iterative Methods</em>, SIAM * </dd> * </dl> * * @since 3.0 */ public abstract class RealLinearOperator { /** * Returns the dimension of the codomain of this operator. * * @return the number of rows of the underlying matrix */ public abstract int getRowDimension(); /** * Returns the dimension of the domain of this operator. * * @return the number of columns of the underlying matrix */ public abstract int getColumnDimension(); /** * Returns the result of multiplying {@code this} by the vector {@code x}. * * @param x the vector to operate on * @return the product of {@code this} instance with {@code x} * @throws DimensionMismatchException if the column dimension does not match * the size of {@code x} */ public abstract RealVector operate(final RealVector x) throws DimensionMismatchException; /** * Returns the result of multiplying the transpose of {@code this} operator * by the vector {@code x} (optional operation). The default implementation * throws an {@link UnsupportedOperationException}. Users overriding this * method must also override {@link #isTransposable()}. * * @param x the vector to operate on * @return the product of the transpose of {@code this} instance with * {@code x} * @throws org.apache.commons.math3.exception.DimensionMismatchException * if the row dimension does not match the size of {@code x} * @throws UnsupportedOperationException if this operation is not supported * by {@code this} operator */ public RealVector operateTranspose(final RealVector x) throws DimensionMismatchException, UnsupportedOperationException { throw new UnsupportedOperationException(); } /** * Returns {@code true} if this operator supports * {@link #operateTranspose(RealVector)}. If {@code true} is returned, * {@link #operateTranspose(RealVector)} should not throw * {@code UnsupportedOperationException}. The default implementation returns * {@code false}. * * @return {@code false} */ public boolean isTransposable() { return false; } } Other Java examples (source code examples)Here is a short list of links related to this Java RealLinearOperator.java source code file: 
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