/*
************************************************************************ 
* EqHeatcsv.java: Solve heat equation using with finite differences
* 
* copyright RH Landau, Oregon State Univ, 8/99 *  
* * 
* comment: Output data saved in file in 3D grid format of gnuplot
* 
* modified 8/01 DH McIntyre to create csv ouput file for Visad spreadsheet
* 
************************************************************************ 
*/ 
 
import java.io.*;                      /* Import input-output Library */ 
 
public class EqHeatcvs 
{ 
 
// Class constants  
public static final int NX = 101;                        /* grid size */ 
public static final int NTIMES = 80000;              /* No iterations */ 
public static final double THC = 0.12;         /* thermal conductivity*/ 
public static final double SPH = 0.113;             /* specific heat */ 
public static final double RHO = 15.;                    /* density */ 
 
// method must throw exceptions if does not handle them. 
public static void main(String[] argv) throws IOException, 
FileNotFoundException  
{  
int ix, t; 
double[] [] u = new double[NX][2]; /* 2-D array declared, allocated */ 
double cons;  
 
// Open file EqHeat.csv for output data, use JDK 1.1 methods  
 
PrintWriter q = new PrintWriter( 
new FileOutputStream("EqHeat.csv"), true); 

/*Print two header lines for VisAd csv (comma separated values) file
* First header gives mapping of domain(x,y) to range (z)
* Second header tells which data appears
* We only ouput z here, so x and y values are assume to go from 
* 0 to (N-1) where N is the number of values (per line for x, # lines for y)
*/
q.println("(position,time)->(temperature)");
q.println("temperature");
 
for(ix=1; ix <= NX-2; ix++) u[ix][0]=100.; /* t=0 all points at 100 C */ 
for(t=0; t < 2; t++) /* except the endpoints */ 
{ 
u[0][t] = 0.; 
u[NX-1][t] = 0.; 
}  
 
cons=THC/(SPH*RHO); /* material constants */ 
 
for(t=1; t <= NTIMES; t++) /* loop over max timesteps */ 
	{ 
	for(ix=1; ix <= NX-2; ix++) /* loop over space */ 
		{ 
		u[ix][1] = u[ix][0]+cons*(u[ix+1][0]+u[ix-1][0]-2.0*u[ix][0]); 
		} 
		if((t%200==0) || (t==1)) /* save every 200 time steps */ 
			{ 
			for(ix=0 ; ix <= NX-1; ix++) 
				{
				q.print(u[ix][1]+" , "); //output data with commas
				}
				q.println();	/* end line of output*/

			} 
	for(ix=1; ix <= NX-2; ix++) u[ix][0]=u[ix][1]; /*shift new values
	to old */ 
}  //end time loop
System.out.println("data stored in EqHeat.csv"); 
 
}  //end main
 
}//end class