samer@1: package eg.maths;
samer@1: import  samer.core.*;
samer@1: import  samer.maths.*;
samer@1: import  samer.maths.ops.*;
samer@1: 
samer@1: public class QuadraticForm extends FunctionOfVector
samer@1: {
samer@1: 	VVector				x, yy;
samer@1: 	Matrix				A;
samer@1: 	MatrixTimesVector	Ax;
samer@1: 	double []			y;
samer@1: 
samer@1: 	public QuadraticForm() { this(Shell.getInt("dimensions",2)); }
samer@1: 	public QuadraticForm(int n) 
samer@1: 	{
samer@1: 		x = new VVector("x",n);
samer@1: 		yy = new VVector("y",n);
samer@1: 		A = new  Matrix("A",n,n);
samer@1: 		Ax = new MatrixTimesVector(yy.array(),A);
samer@1: 		y = yy.array();
samer@1: 
samer@1: 		Shell.put("functionOfVector",this);
samer@1: 		Shell.put("vector",x);
samer@1: 	}
samer@1: 
samer@1: 	public double apply(double [] x) 
samer@1: 	{ 
samer@1: 		Ax.run(x); 
samer@1: 		return -0.5*Mathx.dot(x,y);
samer@1: 	}
samer@1: 
samer@1: 	public VectorFunctionOfVector derivative() 
samer@1: 	{	
samer@1: 		return new VectorFunctionOfVector() {
samer@1: 
samer@1: 			public void apply(double [] x) {
samer@1: 				Ax.run(x);
samer@1: 				Mathx.copy(y,x);
samer@1: 			}
samer@1: 
samer@1: 			public void apply(double [] x, double [] v) {
samer@1: 				Ax.run(x);
samer@1: 				Mathx.copy(y,v);
samer@1: 			}
samer@1: 		};
samer@1: 	}
samer@1: }