// deriv1D.java  compute derivative D=U'(x) given U(x) and x arrays
//               uses nuderiv.java

class deriv1D
{
  deriv1D(int order, int np, int nx, double x[], double U[], double D[])
  {
    double cx[] = new double[np];
    double xg[] = new double[np];
    double deriv;
    boolean debug = false;

    if(debug)
    {
      System.out.println("deriv1D order="+order+", np="+np+", nx="+nx);
      System.out.println("x[0]="+x[0]+", x[1]="+x[1]+", x[2]="+x[2]);
      System.out.println("U[0]="+U[0]+", U[1]="+U[1]+", U[2]="+U[2]);
    }
    for(int j=0; j<np; j++) xg[j] = x[j]; // xg used by nuderiv
    for(int i=0; i<(np+1)/2; i++) // initial region
    {
      new nuderiv(order, np, i, xg, cx);
      deriv = 0.0;
      for(int k=0; k<np; k++) deriv += cx[k]*U[k]; // raw k OK
      D[i] = deriv; 
      if(debug) System.out.println("i="+i+", D="+D[i]);
    } // i

    for(int i=(np+1)/2; i<nx-(np/2); i++) // mid region
    {
      for(int j=0; j<np; j++)
      {
        xg[j]=x[i+j-(np+1)/2];
        if(debug && i==(np+1)/2) System.out.println("j="+j+", xg="+xg[j]);
      }

      for(int j=0; j<np; j++)
      {
	new nuderiv(order, np, (np+1)/2, xg, cx);
        if(debug && j==0 && i<np)
	{
	  if(debug) System.out.println("i="+i+", j="+j+", pt="+((np+1)/2));
	  for(int k=0; k<np; k++)
	    if(debug) System.out.println("k="+k+",cx[k]="+cx[k]+", U="+
                                         U[i+k-(np-1)/2]+", xg="+xg[k]);
	}
        deriv = 0.0;
	for(int k=0; k<np; k++) deriv += cx[k]*U[i+k-(np+1)/2];
        D[i] = deriv; 

      } // j
    } // i

    for(int j=0; j<np; j++) xg[j] = x[nx-np+j]; // xg used by nuderiv
    if(debug)
      for(int j=0; j<np; j++) System.out.println("ix="+(nx-np+j)+", x="+
                                               x[nx-np+j]);
    for(int i=nx-(np/2); i<nx; i++) // final region
    {
	if(debug) System.out.println("i="+i+", point="+(i-nx+np));

      new nuderiv(order, np, i-nx+np, xg, cx);
      deriv = 0.0;
      for(int k=0; k<np; k++) deriv += cx[k]*U[nx-np+k];
      D[i] = deriv; 
      if(debug) System.out.println("i="+i+", D="+D[i]);
    } // i
  } // end deriv1D
} // end class deriv1D