/*
 * 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.optimization.linear;

import java.util.Collection;

import org.apache.commons.math.optimization.GoalType;
import org.apache.commons.math.optimization.OptimizationException;
import org.apache.commons.math.optimization.RealPointValuePair;

/**
 * This interface represents an optimization algorithm for linear problems.
 * <p>
 * Optimization algorithms find the input point set that either {@link GoalType
 * maximize or minimize} an objective function. In the linear case the form of
 * the function is restricted to
 * 
 * <pre>
 * c<sub>1</sub>x<sub>1</sub> + ... c<sub>n</sub>x<sub>n</sub> = v
 * </pre>
 * 
 * and there may be linear constraints too, of one of the forms:
 * <ul>
 * <li>c<sub>1</sub>x<sub>1</sub> + ... c<sub>n</sub>x<sub>n</sub> = v</li>
 * <li>c<sub>1</sub>x<sub>1</sub> + ... c<sub>n</sub>x<sub>n</sub> &lt;= v</li>
 * <li>c<sub>1</sub>x<sub>1</sub> + ... c<sub>n</sub>x<sub>n</sub> >= v</li>
 * <li>l<sub>1</sub>x<sub>1</sub> + ... l<sub>n</sub>x<sub>n</sub> +
 * l<sub>cst</sub> = r<sub>1</sub>x<sub>1</sub> + ... r<sub>n</sub>x<sub>n</sub>
 * + r<sub>cst</sub></li>
 * <li>l<sub>1</sub>x<sub>1</sub> + ... l<sub>n</sub>x<sub>n</sub> +
 * l<sub>cst</sub> &lt;= r<sub>1</sub>x<sub>1</sub> + ...
 * r<sub>n</sub>x<sub>n</sub> + r<sub>cst</sub></li>
 * <li>l<sub>1</sub>x<sub>1</sub> + ... l<sub>n</sub>x<sub>n</sub> +
 * l<sub>cst</sub> >= r<sub>1</sub>x<sub>1</sub> + ...
 * r<sub>n</sub>x<sub>n</sub> + r<sub>cst</sub></li>
 * </ul>
 * where the c<sub>i</sub>, l<sub>i</sub> or r<sub>i</sub> are the coefficients
 * of the constraints, the x<sub>i</sub> are the coordinates of the current
 * point and v is the value of the constraint.
 * </p>
 * 
 * @version $Revision$ $Date$
 * @since 2.0
 */
public interface LinearOptimizer {

	/**
	 * Set the maximal number of iterations of the algorithm.
	 * 
	 * @param maxIterations
	 *            maximal number of function calls
	 */
	void setMaxIterations(int maxIterations);

	/**
	 * Get the maximal number of iterations of the algorithm.
	 * 
	 * @return maximal number of iterations
	 */
	int getMaxIterations();

	/**
	 * Get the number of iterations realized by the algorithm.
	 * <p>
	 * The number of evaluations corresponds to the last call to the
	 * {@link #optimize(LinearObjectiveFunction, Collection, GoalType, boolean)
	 * optimize} method. It is 0 if the method has not been called yet.
	 * </p>
	 * 
	 * @return number of iterations
	 */
	int getIterations();

	/**
	 * Optimizes an objective function.
	 * 
	 * @param f
	 *            linear objective function
	 * @param constraints
	 *            linear constraints
	 * @param goalType
	 *            type of optimization goal: either {@link GoalType#MAXIMIZE} or
	 *            {@link GoalType#MINIMIZE}
	 * @param restrictToNonNegative
	 *            whether to restrict the variables to non-negative values
	 * @return point/value pair giving the optimal value for objective function
	 * @exception OptimizationException
	 *                if no solution fulfilling the constraints can be found in
	 *                the allowed number of iterations
	 */
	RealPointValuePair optimize(LinearObjectiveFunction f, Collection<LinearConstraint> constraints, GoalType goalType,
			boolean restrictToNonNegative) throws OptimizationException;

}
