/*
 * Copyright 2011-2013 JOptimizer
 *
 *   Licensed 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 com.joptimizer.functions;

import java.util.ArrayList;
import java.util.List;

import org.apache.commons.math3.linear.Array2DRowRealMatrix;
import org.apache.commons.math3.linear.ArrayRealVector;
import org.apache.commons.math3.linear.MatrixUtils;
import org.apache.commons.math3.linear.RealMatrix;
import org.apache.commons.math3.linear.RealVector;

/**
 * Generalized logarithm barrier function for SOCP with constraints: 
 * 
||Ai.x+bi|| < ci.x+di, i=1,...,m
 *
 * @see "S.Boyd and L.Vandenberghe, Convex Optimization, p. 600"
 * @author alberto trivellato (alberto.trivellato@gmail.com)
 */
public class SOCPLogarithmicBarrier implements BarrierFunction {

	private List socpConstraintParametersList = null;
	private int dim = -1;

	public SOCPLogarithmicBarrier(List socpConstraintParametersList, int dim) {
		this.socpConstraintParametersList = socpConstraintParametersList;
		this.dim = dim;
	}

	public double value(double[] X) {
		RealVector x = new ArrayRealVector(X);
		
		double ret = 0;
		for(int i=0; i||Ai.x+bi|| < ci.x+di+t, i=1,...,m
	 * @see "S.Boyd and L.Vandenberghe, Convex Optimization, 11.6.2"
	 */
	public BarrierFunction createPhase1BarrierFunction(){
		
		final int dimPh1 = dim +1;
		List socpConstraintParametersPh1List = new ArrayList();
 		SOCPLogarithmicBarrier bfPh1 = new SOCPLogarithmicBarrier(socpConstraintParametersPh1List, dimPh1);
 		
 		for(int i=0; i||A.x+b|| < c.x+d
	 *
	 */
	public class SOCPConstraintParameters{
		private RealMatrix A = null;
		private RealVector b;
		private RealVector c;
		private double d;
		
		public SOCPConstraintParameters(double[][] AMatrix, double[] bVector, double[] cVector, double d){
			this.A = new Array2DRowRealMatrix(AMatrix);
			this.b = new ArrayRealVector(bVector);
			this.c = new ArrayRealVector(cVector);
			this.d = d;;
		}
		
		public RealMatrix getA() {
			return A;
		}
		public RealVector getB() {
			return b;
		}
		public RealVector getC() {
			return c;
		}
		public double getD() {
			return d;
		}
	}

	public double getDualityGap(double t) {
		return ((double)this.socpConstraintParametersList.size()) / t;
	}

}