/*
 * 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.math.analysis.solvers;

import org.apache.commons.math.FunctionEvaluationException;
import org.apache.commons.math.MaxIterationsExceededException;
import org.apache.commons.math.analysis.UnivariateRealFunction;

/**
 * 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>
 * 
 * @version $Revision$ $Date$
 */
public class BisectionSolver extends UnivariateRealSolverImpl {

	/**
	 * Construct a solver for the given function.
	 * 
	 * @param f
	 *            function to solve.
	 * @deprecated as of 2.0 the function to solve is passed as an argument to
	 *             the {@link #solve(UnivariateRealFunction, double, double)} or
	 *             {@link UnivariateRealSolverImpl#solve(UnivariateRealFunction, double, double, double)}
	 *             method.
	 */
	@Deprecated
	public BisectionSolver(UnivariateRealFunction f) {
		super(f, 100, 1E-6);
	}

	/**
	 * Construct a solver.
	 * 
	 */
	public BisectionSolver() {
		super(100, 1E-6);
	}

	/** {@inheritDoc} */
	@Deprecated
	public double solve(double min, double max, double initial)
			throws MaxIterationsExceededException, FunctionEvaluationException {
		return solve(f, min, max);
	}

	/** {@inheritDoc} */
	@Deprecated
	public double solve(double min, double max) throws MaxIterationsExceededException, FunctionEvaluationException {
		return solve(f, min, max);
	}

	/** {@inheritDoc} */
	public double solve(final UnivariateRealFunction f, double min, double max, double initial)
			throws MaxIterationsExceededException, FunctionEvaluationException {
		return solve(min, max);
	}

	/** {@inheritDoc} */
	public double solve(final UnivariateRealFunction f, double min, double max)
			throws MaxIterationsExceededException, FunctionEvaluationException {

		clearResult();
		verifyInterval(min, max);
		double m;
		double fm;
		double fmin;

		int i = 0;
		while (i < maximalIterationCount) {
			m = UnivariateRealSolverUtils.midpoint(min, max);
			fmin = f.value(min);
			fm = f.value(m);

			if (fm * fmin > 0.0) {
				// max and m bracket the root.
				min = m;
			} else {
				// min and m bracket the root.
				max = m;
			}

			if (Math.abs(max - min) <= absoluteAccuracy) {
				m = UnivariateRealSolverUtils.midpoint(min, max);
				setResult(m, i);
				return m;
			}
			++i;
		}

		throw new MaxIterationsExceededException(maximalIterationCount);
	}
}
