gauss_seidal.c

#include<stdio.h>
#include<math.h>
#define X3(x1, x2) ((25 - 12 * (x1) +3 * (x2)) / 20) 
#define X1(x2, x3) ((17 + 2 * (x3) - x2) / 20) 
#define X2(x1, x3) ((-18 + 2 - (3*x1)) / 20)
 
int main() 
{ 
      double allowed_error;
      double x1 = 0, x2 = 0, x3 = 0, y1 = 0, y2 = 0, y3 = 0; 
      int count = 0; 
      printf("Enter value for Allowed Error:\t");
      scanf("%lf", &allowed_error);
      printf("\nx1\t\tx2\t\tx3"); 
      printf("\n%f\t%f\t%f", x1, x2, x3); 
      do 
      { 
            y1 = X1(x2, x3); 
            y2 = X2(y1, x3); 
            y3 = X3(y1, y2); 
            if(fabs(y1 - x1) < allowed_error && fabs(y2 - x2) < allowed_error && fabs(y3 - x3) < allowed_error) 
            {
                  printf("\n\nx1 = %.lf", y1); 
                  printf("\nx2 = %.2lf", y2); 
                  printf("\nx3 = %.2lf", y3); 
                  count = 1; 
            } 
            else 
            { 
                  x1 = y1; 
                  x2 = y2; 
                  x3 = y3; 
                  printf("\n%f\t%f\t%f", x1, x2, x3); 
            } 
      }while(count != 1); 
      return 0;
}