#include <pthread.h>
#include <iostream>

using namespace std;

struct ARGS
{
	int num_thread;
	int n, p;
	double *number;
	pthread_t *thread;
};

void *function_thread(void *pa)
{
	ARGS *arg = (ARGS *)pa;
	double *status_addr;
	int i = 1, num_thread = arg->num_thread;
	int j = 0, count;

	if (fmod(log(arg->p), log(2)) == 0.0) count = log(arg->p) / log(2);
	else count = log(arg->p) / log(2) + 1;

	for (int i = 1; i < arg->n; i++) arg->number[0] += arg->number[i];

	while (j < count)
	{
		if (num_thread % 2 == 0 && arg->num_thread != arg->p - 1)
		{
			if (pthread_join(arg->thread[arg->num_thread + i], (void **)&status_addr))
			{
				cout << "function_thread: Ошибка при выполнении функции pthread_join\n";
				exit(0);
			}

			arg->number[0] += *status_addr;
			num_thread /= 2;
			i *= 2;
			j++;
		}
		else break;
	}

	return arg->number;
}

int main()
{
	setlocale(LC_ALL, "Russian");

	int n, p;
	double *number, *result;
	int index = 0, dev, mod, denom = 1;
	pthread_t *thread;
	ARGS *args;

	cout << "Укажите число элементов последовательности: ";
	cin >> n;

	cout << "Укажите число задач: ";
	cin >> p;

	dev = n / p;
	mod = n % p;

	number = (double *)malloc(n * sizeof(double));

	for (int i = 0; i < n; i++)
	{
		if (i % 2 == 0) number[i] = 1.0 / denom;
		else number[i] = -1.0 / denom;

		denom += 2;
	}

	thread = (pthread_t *)malloc(p * sizeof(pthread_t));
	args = (ARGS *)malloc(p * sizeof(ARGS));


	for (int i = 0; i < p; i++)
	{
		args[i].num_thread = i;
		args[i].thread = thread;
		args[i].p = p;
		args[i].n = dev;
		if (mod > 0)
		{
			args[i].n++;
			mod--;
		}

		args[i].number = (double *)malloc(args[i].n * sizeof(double));
		
		for (int j = 0; j < args[i].n; j++)
		{
			args[i].number[j] = number[index];
			index++;
		}

		if (pthread_create(thread + i, 0, function_thread, args + i))
		{
			cout << "Ошибка при выполнении функции pthread_create\n";
			return 3;
		}
	}

	if (pthread_join(thread[0], (void **)&result))
	{
		cout << "Ошибка при выполнении функции pthread_join\n";
		return 4;
	}

	cout << "Результат: " << *result * 4 << endl;

	free(number);
	free(thread);
	for (int i = 0; i < p; i++) free(args[i].number);
	free(args);

	return 0;
}