Gauss_Seidel.c

#include<stdio.h>
#include<stdlib.h>
#include<stdbool.h>

#define N 110
double old_x[N];
double new_x[N];
double a[N][N];
double b[N];
double e = 0.0001;

double cal_new_x(int i, int n)
{
    int j;
    double res = b[i];
    for(j = 1 ; j<=n; ++j)
    {
        if(j<i)
            res -= a[i][j]*new_x[j];
        if(j>i)
            res -= a[i][j]*old_x[j];
    }
    return res/a[i][i];
}

bool check(int n)
{
    int i ,j;
    for(i = 1 ; i<=n ; ++i)
    {
        if(fabs(old_x[i] - new_x[i]) > e)
            return false;
    }
    return true;

}

int solve(int n)
{
    int i,j;
    int k = 0;
    while(1)
    {
        k++;
        for(i = 1 ; i<=n ; ++i)
        {
            new_x[i] = cal_new_x(i,n);
        }
        if(check(n))
            return k;
        for(i = 1; i<=n ; ++i)
            old_x[i] = new_x[i];

    }
    return -1;

}
signed main()
{
    int i , j , p , q , n;
    printf("\t--GAUSS SEIDEL ITERATIVE METHOD--\n\n");

    printf("Enter number of unknowns: ");
    scanf("%d", &n);
    printf("Enter the augmented matrix: \n");
    for(i = 1 ; i<=n ; ++i)
    {
        for(j = 1 ; j<=n ; ++j)
        {
            scanf("%lf" , &a[i][j]);
        }
        scanf("%lf" , &b[i]);
    }

    int k = 0;
    for(i = 1 ; i<=n ; ++i)
        old_x[i] = 0;

    int total_iteration = solve(n);

    printf("\n");
    for(i = 1 ; i<=n ; ++i)
    {
        printf("x%d = %.4lf\n", i , new_x[i]);
    }
    printf("\nTotal Iteration(k) = %d\n\n", total_iteration);

    return 0;
}