code: public static void jacobian_Control4( DMatrixRMaj L_full ,
  										  double beta[] , DMatrixRMaj A )
  	{
  		int indexA = 0;
  
  		double b0 = beta[0]; double b1 = beta[1]; double b2 = beta[2]; double b3 = beta[3];
  
  		final double ld[] = L_full.data;
  
  		for( int i = 0; i < 6; i++ ) {
  			int li = L_full.numCols*i;
  			A.data[indexA++] = 2*ld[li+0]*b0 +   ld[li+1]*b1 +   ld[li+2]*b2 +   ld[li+3]*b3;
  			A.data[indexA++] =   ld[li+1]*b0 + 2*ld[li+4]*b1 +   ld[li+5]*b2 +   ld[li+6]*b3;
  			A.data[indexA++] =   ld[li+2]*b0 +   ld[li+5]*b1 + 2*ld[li+7]*b2 +   ld[li+8]*b3;
  			A.data[indexA++] =   ld[li+3]*b0 +   ld[li+6]*b1 +   ld[li+8]*b2 + 2*ld[li+9]*b3;
  		}
  	}
docs: Computes the Jacobian given 4 control points.