/* one particle - quantum lattice gas model 1D */
/* coded by Ikeuchi Mitsuru     */
/* ver 0.0.1   2004.12.18       */

import java.awt.*;
import java.awt.event.*;
import java.applet.*;

public class quantumLatticeGas1D extends Applet
  implements ActionListener, AdjustmentListener, Runnable {

/* -------------------------------------- set global ------ */

  Button bt_reset, bt_start, bt_stop;
  Scrollbar sc_ww, sc_wh, spx;
  Thread th = null;

  Dimension dim;
  Image imgOff;
  Graphics gOff;

  int sleepTime = 30;

  int started = 1;
  double px0 = 1.0;


  double t = 0.0;
  double dx = 16.0/256.0;

  double dt = 1.0;

  int now = 0;

  int NNx = 256;
  double psi[][][][] = new double[2][2][NNx][2];

  double phRe[] = new double[NNx];
  double phIm[] = new double[NNx];  

  double vv[] = new double[NNx];

  int NN = NNx+1;
  double aaRe[] = new double[NN];
  double aaIm[] = new double[NN];
  double bbRe[] = new double[NN];
  double bbIm[] = new double[NN];
  double bRe[] = new double[NN];
  double bIm[] = new double[NN];
  double uRe[] = new double[NN];
  double uIm[] = new double[NN];

  int xpts[] = new int[NN];
  int ypts[] = new int[NN];

/* ----------------------------- applet control ------ */

  public void init() {

    resize(630,300);
    setBackground(Color.white);

    dim = getSize();
    imgOff = createImage(dim.width,dim.height);
    gOff = imgOff.getGraphics();

    bt_reset= new Button("reset");
    bt_reset.addActionListener(this);

    bt_start= new Button("start");
    bt_start.addActionListener(this); 

    bt_stop = new Button("stop");
    bt_stop.addActionListener(this);

    sc_ww= new Scrollbar(Scrollbar.HORIZONTAL,30,10,0,110);
    sc_ww.addAdjustmentListener(this);

    sc_wh= new Scrollbar(Scrollbar.HORIZONTAL,85,10,0,160);
    sc_wh.addAdjustmentListener(this);

    spx= new Scrollbar(Scrollbar.HORIZONTAL,60,10,0,110);
    spx.addAdjustmentListener(this);

    setLayout(new BorderLayout());
    Panel pnl = new Panel();
    pnl.setLayout(new GridLayout(1,6,5,0));
    pnl.add(bt_reset);
    pnl.add(bt_start);
    pnl.add(bt_stop);
    pnl.add(new Label("  "));
    pnl.add(new Label("  "));
    pnl.add(spx);
    add(pnl,"North");

    setInitialCondition();
  }

  public void start() {
    if (th == null) {
      th = new Thread(this);
      th.start();
    }
  }

  public void stop() {
    if (th != null) {
      th.stop();
      th = null;
    }
  }

  public void actionPerformed(ActionEvent ev){
    if(ev.getSource() == bt_reset){ 
      t = 0.0;
      setInitialCondition();
      started = 0;
    } else if(ev.getSource() == bt_start){ 
      started = 1;
    } else if(ev.getSource() == bt_stop){
      started = 0;
    }
		}

  public void adjustmentValueChanged(AdjustmentEvent ev){
    if (ev.getSource() == spx) { 
      px0 = 0.1*(double)(spx.getValue())-5.0;
      setInitialCondition();
    }
  }

  public void run() {
    while (th != null) {
      try {
        timeEvolution();
        offPaint();
        repaint();
        Thread.sleep(sleepTime);
      } catch (InterruptedException e) { }
    }
  }

  public void update(Graphics g) {
    paint(g);
  }

  public void paint(Graphics g) {
    g.drawImage(imgOff,0,0,this);
  }

/* ----------------------------- offPaint -------------------- */

  void offPaint() {
    int i,gbx,gby;
    double v1,v2,ph2,y,z;
    double p0,p1,nrm;

    gOff.setColor(Color.white);
    gOff.fillRect(0,0,dim.width,dim.height);

    gbx = 30;
    gby = 220;

/*
    gOff.setColor(Color.cyan);
	for (i=1; i<NNx-1; i++) {
	  p0 = psi[now][0][i][0]*psi[now][0][i][0]+psi[now][0][i][1]*psi[now][0][i][1];
	  p1 = psi[now][1][i][0]*psi[now][1][i][0]+psi[now][1][i][1]*psi[now][1][i][1];
      ph2 = 200.0*(p0+p1);
      if (ph2>=0.5) {
        gOff.drawLine(gbx+i,gby-(int)(ph2+0.5), gbx+i, gby);
	  }
    }
*/

    gOff.setColor(Color.cyan);
	nrm = norm();
	for (i=1; i<NNx-1; i++) {
	  p0 = psi[now][0][i][0]+psi[now][1][i][0];
	  p1 = psi[now][0][i][1]+psi[now][1][i][1];
      ph2 = 200.0*(p0*p0+p1*p1)/nrm;
      if (ph2>=0.5) {
        gOff.drawLine(gbx+i,gby-(int)(ph2+0.5), gbx+i, gby);
	  }
    }

/*
    for (i=0; i<NNx; i++) { 
      y = 30.0*(psi[now][0][i][0]+psi[now][1][i][0]);
      z = 30.0*(psi[now][1][i][1]+psi[now][1][i][1]);
      xpts[i] = gbx+i-(int)(0.5*z);
      ypts[i] = gby+(int)(0.5*z)-(int)(y);
    }
    gOff.setColor(Color.getHSBColor(0.33f,0.9f,0.6f));
    for (i=0; i<NNx-2; i++) {
      gOff.drawLine(xpts[i],ypts[i],xpts[i+1],ypts[i+1]);
    }
*/
    gOff.setColor(Color.blue);
    gOff.drawString("t="+(int)(t+0.5)+" ",10,40);
    gOff.drawString("p0="+(int)(px0*100.0+0.5)/100.0+" ",630/6*5+10,40);

    gbx = 330;
    gby = 60;
    gOff.setColor(Color.black);
    gOff.drawString("quantum lattice gas automata rules",gbx,gby);
    gOff.drawString("u0(t+1,x)=cosTh*u0(t,x+1)+i*sinTh*u1(t,x-1)",gbx,gby+20);
    gOff.drawString("u1(t+1,x)=i*sinTh*u0(t,x+1)+sinTh*u1(t,x-1)",gbx,gby+40);
    gOff.drawString("Th=Pi/4",gbx,gby+60);
    gOff.drawString("u(t,x) = u0(t,x)+u1(t,x) ",gbx,gby+80);
    gOff.drawString("norm=sum(|ui(t,x)|^2,{i=0,1; x=0..,N-1})",gbx,gby+100);
    gOff.setColor(Color.blue);
    gOff.drawString("norm="+normPsi()+" ",gbx,gby+120);
	
  }
/*-------------------------- statistics ----------*/

  double norm() {
    int i;
    double s,p0,p1;

    s = 0.0;
	for (i=0; i<NNx; i++) {
	  p0 = psi[now][0][i][0]+psi[now][1][i][0];
	  p1 = psi[now][0][i][1]+psi[now][1][i][1];
      s += p0*p0+p1*p1;
    }
    return ( s*dx );
  }

  double normPsi() {
    int i;
    double s,pRe,pIm;

    s = 0.0;
	for (i=0; i<NNx; i++) {
      s += psi[now][0][i][0]*psi[now][0][i][0]+psi[now][0][i][1]*psi[now][0][i][1];
	  s += psi[now][1][i][0]*psi[now][1][i][0]+psi[now][1][i][1]*psi[now][1][i][1];
    }
    return ( s*dx );
  }

/*-------------------------- set initial condition ----------*/

  void setInitialCondition() {
    t = 0.0;
    setWave(8.0, 0.8, px0);
  }

/* ----------------------------- set potential -------------- */


/* ----------------------------- set wave packet -------------- */

  void setWave(double wavePos, double waveWidth, double momentum) {
    int i,nxt;
    double a,x,phAb,phPh;

    nxt = (now+1)%2;
    a = Math.pow(2.0*Math.PI*waveWidth*waveWidth,-0.25);
    for (i=1;i<NNx-1;i++) {
      x = i*dx;
      phAb = a*Math.exp(-((x-wavePos)/(2.0*waveWidth))*((x-wavePos)/(2.0*waveWidth)));
      phPh = momentum*x;
      psi[nxt][0][i][0] = phAb*Math.cos(phPh);
      psi[nxt][0][i][1] = phAb*Math.sin(phPh);
    }
    psi[nxt][0][0][0] = 0.0;
    psi[nxt][0][0][1] = 0.0;
    psi[nxt][0][NNx-1][0] = 0.0;
    psi[nxt][0][NNx-1][1] = 0.0;

    a = 0.0;
	for (i=0; i<NNx; i++) {
      a += psi[nxt][0][i][0]*psi[nxt][0][i][0]+psi[nxt][0][i][1]*psi[nxt][0][i][1];
    }
    a = a*dx;

    for (i=0;i<NNx;i++) {
      psi[nxt][0][i][0] = psi[nxt][0][i][0]/a;
      psi[nxt][0][i][1] = psi[nxt][0][i][1]/a;
    }

    for (i=0;i<NNx;i++) {
      psi[nxt][1][i][0] = 0.0;
      psi[nxt][1][i][1] = 0.0;
    }
  }

/* ----------------------------- timeEvolution -------------- */

  void timeEvolution() {
    int i;

    if (started==1) {
	
	  t = t + dt;

	  for (i=0; i<4; i++) {
        timeStep();
	  }
    }
  }

/* ----------------------------- time step -------------- */

  void timeStep() {
    int i,nxt,ip,im;
    double p0mRe,p0mIm,p0pRe,p0pIm,p1mRe,p1mIm,p1pRe,p1pIm;
    double theta,cth,sth;

    now = (now+1)%2;
    nxt = (now+1)%2;

    theta = -Math.PI/4.0;
    sth = Math.sin(theta);
    cth = Math.cos(theta);

    for (i=0; i<NNx; i++) {
      ip = (i+1)%NNx;
      im = (i+NNx-1)%NNx;
      p0mRe = psi[now][0][im][0]; p0mIm = psi[now][0][im][1];
      p1mRe = psi[now][1][im][0]; p1mIm = psi[now][1][im][1];
      p0pRe = psi[now][0][ip][0]; p0pIm = psi[now][0][ip][1];
      p1pRe = psi[now][1][ip][0]; p1pIm = psi[now][1][ip][1];
      psi[nxt][0][i][0] =  cth*p0pRe -sth*p1mIm;
      psi[nxt][0][i][1] =  cth*p0pIm +sth*p1mRe;
      psi[nxt][1][i][0] = -sth*p0pIm +cth*p1mRe;
      psi[nxt][1][i][1] =  sth*p0pRe +cth*p1mIm;
    }
  }



/* ----------------------------- end of applet -------------- */

}