Kizingiti (tarakilishi)

Katika utarakilishi, kizingiti ni jinsi ya ulandanishi (kwa Kiingereza: barrier in computer science). Neno kizingiti linamaanisha kwamba amri ya tarakilishi haiwezi kuendelea ikiwa amri za awali hazifanyiki.

Mfano

Amri hii ya C++ inatumia vizingiti :

struct barrier_type

{

    // how many processors have entered the barrier

    // initialize to 0

    int arrive_counter;

    // how many processors have exited the barrier

    // initialize to p

    int leave_counter;

    int flag;

    std::mutex lock;

};


// barrier for p processors

void barrier(barrier_type* b, int p)

{

    b->lock.lock();

    if (b->leave_counter == p)

    {

        if (b->arrive_counter == 0) // no other threads in barrier

        {

            b->flag = 0; // first arriver clears flag

        }

        else

        {

            b->lock.unlock();

            while (b->leave_counter != p); // wait for all to leave before clearing

            b->lock.lock();

            b->flag = 0; // first arriver clears flag

        }

    }

    b->arrive_counter++;

    int arrived = b->arrive_counter;

    b->lock.unlock();

    if (arrived == p) // last arriver sets flag

    {

        b->arrive_counter = 0;

        b->leave_counter = 1;

        b->flag = 1;

    }

    else

    {

        while (b->flag == 0); // wait for flag

        b->lock.lock();

        b->leave_counter++;

        b->lock.unlock();

    }

}

Marejeo

• Petzell, M. (2005). Expanding the Swahili vocabulary. Africa & Asia, 5, 85-107.

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