1 /*
2 * Copyright (C) 2023 Alberto Irurueta Carro (alberto@irurueta.com)
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16 package com.irurueta.numerical.integration;
17
18 import com.irurueta.numerical.EvaluationException;
19 import com.irurueta.numerical.SingleDimensionFunctionEvaluatorListener;
20
21 /**
22 * This is an exact replacement for MidPointQuadrature, except that upper limit is assumed to be
23 * infinite. It is assumed that the function decreases exponentially rapidly at infinity.
24 */
25 public class ExponentialMidPointQuadrature extends MidPointQuadrature {
26 /**
27 * Constructor.
28 *
29 * @param a Lower limit of integration.
30 * @param listener listener to evaluate a single dimension function at required points.
31 */
32 public ExponentialMidPointQuadrature(final double a, final SingleDimensionFunctionEvaluatorListener listener) {
33 super(0.0, Math.exp(-a), listener);
34 }
35
36 /**
37 * Gets type of quadrature.
38 *
39 * @return type of quadrature.
40 */
41 @Override
42 public QuadratureType getType() {
43 return QuadratureType.EXPONENTIAL_MID_POINT;
44 }
45
46 /**
47 * Evaluates function at f(-log(x))/x.
48 *
49 * @param x point where function is evaluated.
50 * @return result of evaluation.
51 * @throws EvaluationException if evaluation fails.
52 */
53 @Override
54 protected double func(final double x) throws EvaluationException {
55 return listener.evaluate(-Math.log(x)) / x;
56 }
57 }