Явная схема теплопроводности

gistfile1.txt

#define _CRT_SECURE_NO_DEPRECATE
#include "stdio.h"
#include "math.h"
#include <iostream>
using namespace std;

double t = 0.006;
double h = 0.1;

double a = 0.0;
double b = 1.0;

int size = 1+(b-a)/h;


double function(double x)
{
	return x*x*(1-x);
}

void set_conditions(double * u)		//Задание начальных условий
{
	for (int i = 0; i*h <= (b-a); i++)
		*(u+i) = function(i*h+a);
}

void get_U_next(double * u, double * U_new)
{
	*(U_new+size - 1) = 0; //Right border condition
	
	for (int i = size-2; i > 0; i--)		//Заполнение внутри
		*(U_new+i) = (*(u+i-1)-*(u+i)*2+*(u+i+1))/(h*h)*t + *(u+i);
	
	*U_new = (*(U_new+1)*4 - *(U_new+2) - 2*h*1)/3; //Left border condition c точностью O(h*h)
	//	O(h) precision:
	//*U_new = *(U_new+1) - h;
}

void main()
{
	FILE * file = fopen("file.txt", "w");
	
	double * u = new double[size * sizeof(double)];
	double * u_next = new double[size * sizeof(double)];
	set_conditions(u);

	double time = 25.0;
	double time_current = 0.0;

	while (time_current < time)			//Пересчет по слоям до определенного времени
	{
		time_current = time_current + t;
		get_U_next(u, u_next);
		for (int i = 0; i < size; i++)
			*(u+i) = *(u_next + i);
	}

	for (int i = 0; i < size; i++)
			fprintf(file, "%e %e\n", i*h, *(u+i));

	return;
}