ser_heat2D.c
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/****************************************************************************
* DESCRIPTION:
* Serial HEAT2D Example - C Version
* This example is based on a simplified
* two-dimensional heat equation domain decomposition. The initial
* temperature is computed to be high in the middle of the domain and
* zero at the boundaries. The boundaries are held at zero throughout
* the simulation. During the time-stepping, an array containing two
* domains is used; these domains alternate between old data and new data.
*
* The physical region, and the boundary conditions, are suggested
by this diagram;
u = 0
+------------------+
| |
u = 100 | | u = 100
| |
+------------------+
u = 100
Interrior point :
u[Central] = (1/4) * ( u[North] + u[South] + u[East] + u[West] )
****************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define N 200
#define M 200
#define ITER_PRINT 100
#define PRINT_DATA 1
#define EPSILON 1e-1
void update(int nx,int ny, float *u, float *unew, float * diff);
void inidat(int nx, int ny, float *u, float *unew);
void prtdat(int nx, int ny, float *u,const char *fnam);
int main(int argc, char *argv[])
{
float diff=1.0;
float *u = (float *)malloc(N * M * sizeof(float));
float *unew = (float *)malloc(N * M * sizeof(float));
if(u==0 || unew ==0)
{
perror("Can't allocated data\n");
return -1;
}
printf ( "\n" );
printf ( "HEATED_PLATE\n" );
printf ( " Serial version\n" );
printf ( " A program to solve for the steady state temperature distribution\n" );
printf ( " over a rectangular plate.\n" );
printf ( "\n" );
printf ( " Spatial grid of %d by %d points.\n\n", M, N );
/* Initialize grid and create input file */
printf("Initializing grid\n");
inidat(N, M,u,unew);
prtdat(N, M,u, "initial.dat");
printf("Start computing\n");
int iter=0;
/*
* iterate until the new solution unew differs from the old solution u
* by no more than EPSILON.
* */
while(diff> EPSILON) {
update(N, M, u, unew,&diff);
if(iter%ITER_PRINT==0)
printf("Iteration %d, diff = %f\n ", iter,diff);
iter++;
}
prtdat(N, M, u, "final.dat");
free(u);
free(unew);
}
/****************************************************************************
* subroutine update
****************************************************************************/
void update(int nx,int ny, float *u, float *unew, float * diff)
{
int ix, iy;
*diff=0.0;
for (ix = 1; ix < nx-1; ix++) {
for (iy = 1; iy < ny-1; iy++) {
unew[ix*ny+iy] =
(u[(ix+1)*ny+iy] + u[(ix-1)*ny+iy] +
u[ix*ny+iy+1] + u[ix*ny+iy-1] )/4.0;
if (*diff < fabs (unew[ix*ny+iy] - u[ix*ny+iy] ))
{
*diff = fabs ( unew[ix*ny+iy] - u[ix*ny+iy] );
}
}
}
for (ix = 1; ix < nx-1; ix++) {
for (iy = 1; iy < ny-1; iy++) {
u[ix*ny+iy] = unew[ix*ny+iy];
}
}
}
/*****************************************************************************
* Initialize Data
*****************************************************************************/
void inidat(int nx, int ny, float *u, float *unew)
{
int ix, iy;
/*
*Set boundary data and interrior values
* */
for (ix = 0; ix < nx; ix++)
for (iy = 0; iy < ny; iy++) {
if(ix==0)
{
u[ix*ny+iy]=0.0;
}
else
if(iy==0 && ix!=0)
{
u[ix*ny+iy]=100.0;
}else
if(ix==nx-1)
{
u[ix*ny+iy]=100.0;
}else
if(iy==ny-1 && ix!=0)
{
u[ix*ny+iy]=100.0;
}else
u[ix*ny+iy]=( float ) ( 2 * nx + 2 * ny - 4 );
}
}
/**************************************************************************
* Print Data to files
**************************************************************************/
void prtdat(int nx, int ny, float *u,const char *fnam)
{
int ix, iy;
FILE *fp;
if(ITER_PRINT==0)return;
fp = fopen(fnam, "w");
for (ix = 0 ; ix < nx; ix++) {
for (iy =0; iy < ny; iy++) {
fprintf(fp, "%8.3f", u[ix*ny+iy]);
if(iy!=ny-1)
{
fprintf(fp, " ");
}else
{
fprintf(fp, "\n");
}
}
}
fclose(fp);
}