| // 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.quadrature.scalar; |
| |
| import org.spaceroots.mantissa.functions.scalar.*; |
| import org.spaceroots.mantissa.functions.FunctionException; |
| import org.spaceroots.mantissa.functions.ExhaustedSampleException; |
| |
| /** This class implements a Riemann integrator as a sample. |
| |
| * <p>A Riemann integrator is a very simple one that assumes the |
| * function is constant over the integration step. Since it is very |
| * simple, this algorithm needs very small steps to achieve high |
| * accuracy, and small steps lead to numerical errors and |
| * instabilities.</p> |
| |
| * <p>This algorithm is almost never used and has been included in |
| * this package only as a simple template for more useful |
| * integrators.</p> |
| |
| * @see RiemannIntegrator |
| |
| * @version $Id$ |
| * @author L. Maisonobe |
| |
| */ |
| |
| public class RiemannIntegratorSampler |
| implements SampledFunctionIterator { |
| |
| /** Underlying sample iterator. */ |
| private SampledFunctionIterator iter; |
| |
| /** Current point. */ |
| private ScalarValuedPair current; |
| |
| /** Current running sum. */ |
| private double sum; |
| |
| /** Constructor. |
| * Build an integrator from an underlying sample iterator. |
| * @param iter iterator over the base function |
| */ |
| public RiemannIntegratorSampler(SampledFunctionIterator iter) |
| throws ExhaustedSampleException, FunctionException { |
| |
| this.iter = iter; |
| |
| // get the first point |
| current = iter.nextSamplePoint(); |
| |
| // initialize the sum |
| sum = 0.0; |
| |
| } |
| |
| public boolean hasNext() { |
| return iter.hasNext(); |
| } |
| |
| public ScalarValuedPair nextSamplePoint() |
| throws ExhaustedSampleException, FunctionException { |
| // performs one step of a Riemann scheme |
| ScalarValuedPair previous = current; |
| current = iter.nextSamplePoint(); |
| sum += (current.getX() - previous.getX()) * previous.getY(); |
| |
| return new ScalarValuedPair(current.getX(), sum); |
| |
| } |
| |
| } |