C Program To Find The Value Using Poison Algorithm | C Programming

C Programming | C Program to find the value using poison algorithm

#include<stdio.h>
#include<conio.h>
#include<math.h>
#define g(x,y) 2*(x)*(x)*(y)*(y)
int main(){
 int n,i,j,k;
 float sum,error,E[10],a[10][10],b[10],new_x[10],old_x[10],tl,tr,tu,tb,h,buffer;
 printf("\nPoision's' \n");
 printf("Enter the dimension of plate\n");
 scanf("%d",&n);
 printf("\nEnter the dimension of grid\n");
 scanf("%f",&h);
 printf("\nEnter the temperatures at left, right, bottom and top of the plate \n");
 scanf("%f%f%f%f",&tl,&tr,&tb,&tu);
 //construction of coefficient matrix
 for(i=0;i<=n;i++)
  a[i][i]=-4;
 for(i=0;i<=n;i++)
  a[i][n-i]=0;
 for(i=0;i<=n;i++)
 for(j=0;j<=n;j++){
  if(i!=j && j!=(n-i))
   a[i][j]=1;
 }
 
 //Construction of RHS vector
 k=0;
 for(i=1;i<n;i++)
 for(j=1;j<n;j++)
  b[k++]=h*h*g(i,j);
 
 k=0;
 for(i=1;i<n;i++){
  for(j=1;j<n;j++){
  
   if((i-1)==0)
    b[k]=b[k]-tl;
    
   if((i+1)==n)
    b[k]=b[k]-tr;
    
   if((j-1)==0)
    b[k]=b[k]-tb;
   
   if((j+1)==n)
    b[k]=b[k]-tu;
    
   k++; 
  }
  
 }
 
 printf("\nEnter accuracy limit\n");
 scanf("%f",&error);
 
 //Solving the system of linear equations using Gauss-Seidel method
 for(i=0;i<=n;i++){
  new_x[i]=0;
 }
 
 while(1){
  for(i=0;i<=n;i++){
   sum=b[i];
   for(j=0;j<=n;j++){
    if(i!=j)
     sum=sum-a[i][j]*new_x[j];
   }
   old_x[i]=new_x[i];
   new_x[i]=sum/a[i][i];
   E[i]=fabs(new_x[i]-old_x[i])/fabs(new_x[i]);
  }
  for(i=0;i<=n;i++){
   if(E[i]>error)
    break;
    
  }
  if(i==(n+1))
   break;
  else
   continue;
   
 }
 
 printf("\nsolution\n");
 for(i=0;i<=n;i++)
 printf("x%d=%6.2f\n",i+1,new_x[i]);
 getch();
 return 0;
}