download: Population.java

package Model;

import viabController.Point;

/**
 * <B>Population model</B>
 * Represents the growth of a population in a limited space.
 * The size of the population x can evolve thanks to a growing rate y.
 * 
 * @author Florent LOPEZ
 */
public class Population extends Dynamic_System {

    Population() {

        this.nbDim_ = 2;
        this.nbDimControl_ = 1;
        this.initSystem();

        this.lowerBoundState_[0] = 0.2f;
        this.upperBoundState_[0] = 3;
        this.lowerBoundState_[1] = -2;
        this.upperBoundState_[1] = 2;
        this.lowerBoundControl_[0] = -0.5f;
        this.upperBoundControl_[0] = 0.5f;
        this.dt_ = 0.2;

        this.theoricCurves_ = true;
        this.nbLineTheoric = 2;
    }

    /**
     * Dynamics: x' = xy
     * y'=u
     */
    @Override
    public Point computePhi(Point inP, Point inU) {
        Point res = new Point(inP.nbDim_);
        res.vect_[ 0] = (float) (inP.vect_[ 0] * inP.vect_[1]);
        res.vect_[ 1] = inU.vect_[ 0];
        return res;
    }

    @Override
    public double fTheoric(double inX, int i) {
        if (i == 1) {
            return Math.sqrt(2 * this.upperBoundControl_[0] * Math.log(this.upperBoundState_[0] / inX));
        } else {
            return -Math.sqrt(2 * this.upperBoundControl_[0] * Math.log(inX / this.lowerBoundState_[0]));
        }
    }

    /**
     * computes the real derivative
     * @param inP normalized point
     * @param inU control
     * @param indice indice
     * @return derivative at the point inP
     */
    @Override
    public Point derivative(Point inP, Point inU, int indice, float betaHNorme) {
        Point res = new Point(inP.nbDim_);
        //inP = this.deNorme(inP);
        res.vect_[0] = (float) 0;
        res.vect_[1] = (float) 1;
        return this.norme(res);
    }
}