N customers enter the bakery to buy cookies. Each customer gets its turn[i], by computing a next number, and waits to be served. The clerk uses a counter to keep track of the served customers. The clerk serves the customer whose turn[i] is equal to the counter. After each serve (), the clerk increments the counter. When the counter reaches N, the clerk considers that it is done and leaves for home. (Shared variables) turn[i] = 0 i = 1, ..., N (N is initialized to 10) number = 0; served [i]=0; counter = 0; customer i() {number++; turn[i] = number; while (!served[i]){}; getServed(); go home;} clerk () {while (counter < N){counter++; for (int j=1; j<=N; j++){if (counter == turn[j]){served[j] = True; serve();//simulated by sleep served[j] = True; serve();//simulated by sleep served[j] = False;//if}//for}//while leave;}//clerk
All customer() and clerk() processes execute concurrently.
a) Is it possible for two customers to compute the same number? Explain. If yes, give the execution sequence that will show it.
b) Under the hypothesis that each customer has computed a different number value, is it possible for customers to compete for the same cookies (because their turn [i] is the same)? Explain. If yes, give the execution sequence that will show it.
c) Under the hypothesis that all customers have their turn [i] set before the clerk starts executing, is it possible for a customer to starve (busy wait forever)? Explain. If yes, give the execution sequence that will show it.
d) Is it possible for the clerk to never go home? Explain. If yes, give the execution sequence that will show it.
e) If there are N cookies on the shelf, is it possible for the clerk to run out of cookies before all the customers got served? Explain. If yes, give the execution sequence that will show it.