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+/*
+ * 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.analysis.solvers;
+
+import org.apache.commons.math3.util.FastMath;
+import org.apache.commons.math3.exception.TooManyEvaluationsException;
+
+/**
+ * Implements the <a href="http://mathworld.wolfram.com/Bisection.html">
+ * bisection algorithm</a> for finding zeros of univariate real functions.
+ * <p>
+ * The function should be continuous but not necessarily smooth.</p>
+ *
+ */
+public class BisectionSolver extends AbstractUnivariateSolver {
+ /** Default absolute accuracy. */
+ private static final double DEFAULT_ABSOLUTE_ACCURACY = 1e-6;
+
+ /**
+ * Construct a solver with default accuracy (1e-6).
+ */
+ public BisectionSolver() {
+ this(DEFAULT_ABSOLUTE_ACCURACY);
+ }
+ /**
+ * Construct a solver.
+ *
+ * @param absoluteAccuracy Absolute accuracy.
+ */
+ public BisectionSolver(double absoluteAccuracy) {
+ super(absoluteAccuracy);
+ }
+ /**
+ * Construct a solver.
+ *
+ * @param relativeAccuracy Relative accuracy.
+ * @param absoluteAccuracy Absolute accuracy.
+ */
+ public BisectionSolver(double relativeAccuracy,
+ double absoluteAccuracy) {
+ super(relativeAccuracy, absoluteAccuracy);
+ }
+
+ /**
+ * {@inheritDoc}
+ */
+ @Override
+ protected double doSolve()
+ throws TooManyEvaluationsException {
+ double min = getMin();
+ double max = getMax();
+ verifyInterval(min, max);
+ final double absoluteAccuracy = getAbsoluteAccuracy();
+ double m;
+ double fm;
+ double fmin;
+
+ while (true) {
+ m = UnivariateSolverUtils.midpoint(min, max);
+ fmin = computeObjectiveValue(min);
+ fm = computeObjectiveValue(m);
+
+ if (fm * fmin > 0) {
+ // max and m bracket the root.
+ min = m;
+ } else {
+ // min and m bracket the root.
+ max = m;
+ }
+
+ if (FastMath.abs(max - min) <= absoluteAccuracy) {
+ m = UnivariateSolverUtils.midpoint(min, max);
+ return m;
+ }
+ }
+ }
+}