// test_deriv1D.java

class test_deriv1D
{
  test_deriv1D()
  {
    int nx = 80;
    double x[] = new double[nx];
    double U[] = new double[nx];
    double D[] = new double[nx];
    int np = 8;
    int order;
    double xmin = -4.0;
    double xmax = +4.0;
    double hx;
    double err, maxerr=0.0;
    boolean debug = false;

    System.out.println("test_deriv1D running");
    System.out.println("nx="+nx+", np="+np+", xmin="+xmin+", xmax="+xmax);

    hx = (xmax-xmin)/(double)(nx-1);
    for(int i=0; i<nx; i++)
    {
      x[i] = xmin+hx*i;
      U[i] = Math.sin(x[i]);
      if(debug) System.out.println("i="+i+",x="+x[i]+", U="+U[i]); 
    }

    order = 1;
    System.out.println("order="+order);
    new deriv1D(order, np, nx, x, U, D);
    for(int i=0; i<nx; i++)
    {
      err = D[i]-Math.cos(x[i]);
      maxerr = Math.max(maxerr, Math.abs(err));
      if(debug) System.out.println("i="+i+", U="+U[i]+", D="+D[i]+", err="+err);
    }
    System.out.println("Ux max error="+maxerr);

    order = 2;
    System.out.println("order="+order);
    new deriv1D(order, np, nx, x, U, D);
    for(int i=np; i<nx-np; i++)
    {
      err = D[i]-(-Math.sin(x[i]));
      maxerr = Math.max(maxerr, Math.abs(err));
      if(debug)
        System.out.println("i="+i+", U="+U[i]+", D="+D[i]+", err="+err);
    }
    System.out.println("Uxx max error="+maxerr);

    order = 3;
    System.out.println("order="+order);
    new deriv1D(order, np, nx, x, U, D);
    for(int i=np; i<nx-np; i++)
    {
      err = D[i]-(-Math.cos(x[i]));
      maxerr = Math.max(maxerr, Math.abs(err));
      if(debug)
        System.out.println("i="+i+", U="+U[i]+", D="+D[i]+", err="+err);
    }
    System.out.println("Uxxx max error="+maxerr);

    order = 4;
    System.out.println("order="+order);
    new deriv1D(order, np, nx, x, U, D);
    for(int i=np; i<nx-np; i++)
    {
      err = D[i]-Math.sin(x[i]);
      maxerr = Math.max(maxerr, Math.abs(err));
      if(debug)
        System.out.println("i="+i+", U="+U[i]+", D="+D[i]+", err="+err);
    }
    System.out.println("Uxxxx max error="+maxerr);
    System.out.println("test_deriv1D finished");
  } // end test_deriv1D

  public static void main (String[] args)
  {
    new test_deriv1D();
  }
} // end class test_deriv1D