/* 
   
   Copyright (C) Bernard Piette 
                 University of Durham (UK) 
                 Department of Mathematical Sciences
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   You can modify or use any part of the source code but only under the  
   condition that this Copyright notice is kept in the resulting source file.
*/
#include <pde_euler.h>
#include <grf_pde.h>
#include <iostream>
#include <iostream>

using namespace std;

// sine-Gordon diffusion Equation 

class dsg_pde : public pde_euler 
{ 
public:
  dsg_pde(double xmin,double xmax,int nx) :
    pde_euler(xmin,xmax,nx)
  {
  }

  // Evaluate the sine-Gordon equation 
  // functions:                     
  // f[0] : f : sine Gordond fct  
  // F : array for result           
  //***********************************
  void Eqn(double &F) 
  { eval_derivatives();

    Force_ = fxx_ - sin(f_[0]);
  }

  // Compute the initial condition. 
  // Fcts_[i]   : f(x_i)          
  //********************************
  void Init(double x,double &F)
  { double xm;
    xm = (Xmin_+Xmax_)*0.5;
    F = exp(-(x-xm)*(x-xm));
  }
};

double xmin = -10.0;
double xmax =  10.0;
double tmax =   5.0;
double grf_dt = 0.5;

int nx      =   101;
char *file_name = "test";

int main(int argc,char **argv)
{ try
  {    // Build a pde for sineGordon
    dsg_pde pde(xmin,xmax,nx);

       // Set dt by hand : dx * par.dt_r
    pde.set_dt(pde.dx()*pde.dx()*0.25);

       // Create a new graphic object
    grf_pde *grfp = new grf_pde(&pde,file_name);
    pde.init_grf(grfp);

       // compute the initial condition
    pde.initial_value();

       // integrate up to tmax;
    pde.integrate_grf_until(tmax,grf_dt);
  }
  catch(string e) 
  { cerr << e << std::endl;
  }
}