Hej, z powodu pandemii muszę jak najszybciej wrócić do Polski, a do poniedziałku muszę zrobić kilka zadań na studia, więc szukam kogoś, kto rozwiąże je wszystkie. Zapłacę oczywiście (jeśli można tutaj ogłaszać tego typu zlecenia za pieniądze)
Niżej przykład zadania. Przewidywany czas rozwiązania zadań to ok. 1.5h (po angielsku)
Cena: 50-200PLN (do negocjacji)
Zadanie:
A bakery shop has to provide a stream of muffins for customers. The muffins are made by a baker in the kitchen and placed on a conveyor belt. The conveyor belt carries the muffins to where the customers are waiting to buy them.
This scenario has been simulated using two processes: the baker and customer, and a shared conveyor belt implemented as a circular array called conveyor, where each space in the array can hold one muffin. There are two shared general semaphores, empty and full, and a mutex buffer_mutex. In this scenario, there is only multiple bakers and a single customer.
The pseudo-code for the baker is as follows. The baker makes use of an integer variable in for noting the next available space on the conveyor belt.
1. while(true){
2. muffin = makeMuffin(); // Create a muffin
3. wait(empty);
4. wait(buffer_mutex);
5. conveyor[in] = muffin; // Put the muffin on the conveyor belt
6. in=(in+1)modn;
7. signal(buffer_mutex);
8. signal(full);
9. }
The pseudo-code for the customer is as follows. The customer makes use of an integer variable out for noting the next location on the conveyor belt that contains a muffin.
1. while(true){
2. wait(full);
3. muffin = conveyor[out]; // Get a muffin from the conveyor belt
4. conveyor[out] = null;
5. out=(out+1)modn;
6. signal(empty);
7. eat(muffin); // Eat the muffin
8. }
This code should be familiar to you as it is similar to the example of the Producer-Consumer problem. Only a few sentences are required for each of the questions below.
(a) (20 marks) Explain, in words, the purpose of the mod n statement. Explain what is the purpose of mutex buffer_mutex. What problems solves? You may wish to include simple examples.
(b) (20 marks) Explain what will happen if the order of semaphores in the customer changes. So, we have in line 2 signal(empty) and in line 6 wait(full). Now assume that there is a single baker and a single customer, with an infinite buffer. Explain, in words, what changes should be made and why.
