C Program to simple iteration method

C Program to simple iteration method

How to Write a C Program to simple iteration method in C Programming Language ?


Solution:


#define _CRT_SECURE_NO_WARNINGS
#include<stdlib.h>
#include<stdio.h>
#include<math.h>
double *xk, *xk1;
double t, l1, l2, max, Axk = 0, eps;
int n, i, j, k, count = 0;;
int compare()
{
 max = abs(xk[0] - xk1[0]);
 for (i = 1; i < n; i++)
 {
  if (abs(xk[i] - xk1[i]) > max)
   max = abs(xk[i] - xk1[i]);
 }
 if (max <= eps) return 1;
 else return 0;
}
int main()
{
 FILE *f1;
 FILE *f2;
 double **a;
 f1 = fopen("input.txt", "r");
 fscanf(f1, "%d", &n);    //считываем размер матрицы коэффициентов
 a = (double**)malloc(n*sizeof(double*));     //выделяем память под матрицу
 for (i = 0; i < n; i++)
  a[i] = (double*)malloc((n + 1)*sizeof(double));
 for (i = 0; i < n; i++)   //заполняем матрицу коэффициентов
  for (j = 0; j <= n; j++)
   fscanf(f1, "%lf", &a[i][j]);
 fscanf(f1, "%lf%lf", &l1, &l2);
 fscanf(f1, "%lf", &eps);
 xk = (double*)malloc(n*sizeof(double));
 xk1 = (double*)malloc(n*sizeof(double));
 for (i = 0; i < n; i++)
 {
  xk[i] = 1;
  xk1[i] = 0;
 }
 t = 2 / (l1 + l2);
 do
 {
  for (i = 0; i < n; i++)
  {
   for (j = 0; j < n; j++)
   {
    Axk += a[i][j] * xk[j];
   }
   xk1[i] = xk[i] - t*(Axk - a[i][n]);
   Axk = 0;
  }
  for (k = 0; k < n; k++)
  {
   xk[k] = xk1[k];
  }
  count++;
 } while (compare() == 0);
 fclose(f1);
 f2 = fopen("output.txt", "w");
 for (i = 0; i < n; i++)
  fprintf(f2, "x[%d] = %.8f\n", i + 1, xk1[i]);
 fprintf(f2, "число итераций = %d", count);
 


 fclose(f2);
 return 0;
}


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