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 it allows for an inverse
23 * square-root singularity in the integrand at the lower limit "a".
24 */
25 public class LowerSquareRootMidPointQuadrature extends MidPointQuadrature {
26
27 /**
28 * Original lower bound of integration.
29 */
30 private final double aOrig;
31
32 /**
33 * Constructor.
34 *
35 * @param a Lower limit of integration.
36 * @param b Upper limit of integration.
37 * @param listener listener to evaluate a single dimension function at required points.
38 */
39 public LowerSquareRootMidPointQuadrature(
40 final double a, final double b, final SingleDimensionFunctionEvaluatorListener listener) {
41 super(0.0, Math.sqrt(b - a), listener);
42 aOrig = a;
43 }
44
45 /**
46 * Gets type of quadrature.
47 *
48 * @return type of quadrature.
49 */
50 @Override
51 public QuadratureType getType() {
52 return QuadratureType.LOWER_SQUARE_ROOT_MID_POINT;
53 }
54
55 /**
56 * Evaluates function at 2*x*f(a0+x^2).
57 *
58 * @param x point where function is evaluated.
59 * @return result of evaluation.
60 * @throws EvaluationException if evaluation fails.
61 */
62 @Override
63 protected double func(final double x) throws EvaluationException {
64 return 2.0 * x * listener.evaluate(aOrig + x * x);
65 }
66 }