Part 1: Producer-Consumer - execution (0 points)

The producer_consumer.cpp program given to you simulates a highly simplified restaurant order taking and processing system using pthreads. Study this program, using the comments in the code to help you understand the functionality.

Build and execute this program multiple times. You will observe that the program behaves strangely:

Some random, dummy orders that were never placed may get processed.

Some orders entered by the user may not be processed at all.

The message Phew! Done with orders for today! may get printed even before orders are placed.

All these problems arise because of lack of synchronization among the processOrders and takeOrders threads.

Part 2: Producer-Consumer - modification (15 points)

Copy producer_consumer.cpp into a new file named producer_consumer_with_synchronization.cpp and modify the copy as instructed below (refer to your prep work videos/slides if you need to help you complete this assignment).

Protect access to shared (i.e., global) data variables used in the processOrders and takeOrders threads. As part of this:

Create a global pthread mutex variable named data_mutex and initialize it to default attributes using the macro provided by the pthread library.

Insert mutex lock/unlock statements before/after regions of code using shared data in the two pthread functions. Note: the beginning and end of all critical regions are marked. Identify and protect critical region(s) that are relevant to this task.

Protect access to the console in the processOrders and takeOrders threads (remember that the console that cin & cout access is a shared resource). As part of this:

Create a global pthread mutex variable named console_mutex and initialize it to default attributes using the macro provided by the pthread library.

Insert mutex lock/unlock statements before/after regions of code where the console is accessed in the two pthread functions. Note: the beginning and end of all critical regions are marked. Identify and protect critical region(s) that are relevant to this task.

Use condition variables to synchronize operations between the processOrders and takeOrders threads. As part of this:

Create necessary global pthread condition variables and initialize all of them to default attributes using the macro provided by the pthread library.

Insert pthread condition wait statements in processOrders and takeOrders threads such that:

no new orders are put into the buffer unless there is at least one space in the buffer, i.e., no new orders are put into the buffer if the buffer is full;

orders are not retrieved from the buffer unless there is at least one new order, i.e., orders are not retrieved if the buffer is empty.

Insert corresponding condition signal statements in processOrders and takeOrders threads so that the above waits will end when the conditions being waited for are satisfied.

In the main function, after both threads are created and before printing the goodbye message, insert code to ensure that the main thread waits for both pthreads to complete.

In the main function, after both threads are created and before printing the goodbye message, insert code to ensure that the main thread waits for both pthreads to complete.

Build and run your program. When prompted, enter 10 unique integers in the range of 1 to 50. If you have put in all synchronization statements correctly, your program must adhere to the following:

Print statements must not be interleaved (i.e., a cout statement in a given thread must be not interrupted by a cout statement in a different thread).

Only orders that have been placed must get processed.

All orders that are placed must get processed, in the order in which they were placed.

Multiple orders may be placed before the first one gets processed.

The message Phew! Done with orders for today! must always be printed and printed last.

Sample Output:

Below is a sample of what your output should look like after adding appropriate synchronization constructs:

the code that is being modify:

#include

#include

#include

#include

using namespace std;

#define MAX 10

#define N 4

// Data structure to represent a simplified Order

// that has an order number and an item number.

struct Order

{

int order_num;

int item_num;

};

Order new_orders [N]; // array of elements of type Order to be used as a shared buffer

int num_new_orders = 0; // count of number of new (i.e., unprocessed) orders

int order_num = 0; // global variable used to generate unique order numbers

// TODO: Define and initialize necessary mutex and condition variables here

void* takeOrders(void* arg)

{

int item;

int index = 0;

for(int i = 0; i

// Beginning of critical region 1

// Get user input

cout

cin >> item;

// Print new order's details

cout

// End of critical region 1

// Beginning of critical region 2

// Put new order into new orders buffer and update number of new orders

new_orders[index].order_num = order_num;

new_orders[index++].item_num = item;

++num_new_orders;

// End of critical region 2

// Update order number so that next order gets a different number

++order_num;

// If the end of the new orders buffer is reached, wrap back around

if(index == N)

index = 0;

}

pthread_exit(NULL);

}

void* processOrders(void* arg)

{

int item;

int index = 0;

int o_num;

for(int i = 0; i

// Beginning of critical region 3

// Retrieve new order details from buffer and update number of new orders

o_num = new_orders[index].order_num;

item = new_orders[index++].item_num;

--num_new_orders;

// End of critical region 3

// Beginning of critical region 4

// Print retrieved order's details

cout

// End of critical region 4

// Suspend self for 1 second

sleep(1);

// If the end of the new orders buffer is reached, wrap back around

if(index == N)

index = 0;

}

pthread_exit(NULL);

}

int main()

{

// Create threads to take and process orders

pthread_t id1, id2;

pthread_create(&id1, NULL, processOrders, NULL);

pthread_create(&id2, NULL, takeOrders, NULL);

// TODO: Add code to wait for both threads to finish

// Print goodbye message

cout

pthread_exit(NULL);

}

Enter a menu iten number between 1 and 50: 2 Got new order! Order number is e and iten number: 2 Processing order number 8 with item number: 2 Enter a menu iten number between 1 and 50: 10 Got new order! Order number is 1 and iten number: 10 Enter a menu iten number between 1 and 50: 43 Got new order! Order number is 2 and iten number: 43 Processing order number 1 with item number: 10 Enter a menu iten number between 1 and 50: 19 Got new order! Order number is 3 and iten number: 19 Enter a menu iten number between 1 and 50: 22 Got new order! Order number is 4 and iten number: 22 Enter a menu iten number between 1 and 50: 40 Got new order! Order number is 5 and iten number: 40 Enter a menu iten number between 1 and 50: 28 Got new order! Order number is 6 and iten number: 28 sequence they were plced Enter a menu iten number between 1 and 50: 15 Got new order! Order number is 7 and iten number: 15 Processing order number 2 with item number: 43 Processing order number 3 with item number: 19 Enter a menu iten number between 1 and 50: 23 Got new order! Order number is 8 and iten number: 23 Processing order number 4 with item number: 22 Enter a menu iten number between 1 and 50: 9 Got new order! Order number is 9 and iten number: 9 Processing order number 5 with item number: 40 Processing order number 6 with item number: 28 Processing order number 7 with item number: 15 Processing order number 8 with item number: 23 Processing order number 9 with item number:9 Orders are processed in the ers for today hariniramaprasad:~/workspace/ITS 6 1 solutions and_grading (master) Must always be printed at the end! Enter a menu iten number between 1 and 50: 2 Got new order! Order number is e and iten number: 2 Processing order number 8 with item number: 2 Enter a menu iten number between 1 and 50: 10 Got new order! Order number is 1 and iten number: 10 Enter a menu iten number between 1 and 50: 43 Got new order! Order number is 2 and iten number: 43 Processing order number 1 with item number: 10 Enter a menu iten number between 1 and 50: 19 Got new order! Order number is 3 and iten number: 19 Enter a menu iten number between 1 and 50: 22 Got new order! Order number is 4 and iten number: 22 Enter a menu iten number between 1 and 50: 40 Got new order! Order number is 5 and iten number: 40 Enter a menu iten number between 1 and 50: 28 Got new order! Order number is 6 and iten number: 28 sequence they were plced Enter a menu iten number between 1 and 50: 15 Got new order! Order number is 7 and iten number: 15 Processing order number 2 with item number: 43 Processing order number 3 with item number: 19 Enter a menu iten number between 1 and 50: 23 Got new order! Order number is 8 and iten number: 23 Processing order number 4 with item number: 22 Enter a menu iten number between 1 and 50: 9 Got new order! Order number is 9 and iten number: 9 Processing order number 5 with item number: 40 Processing order number 6 with item number: 28 Processing order number 7 with item number: 15 Processing order number 8 with item number: 23 Processing order number 9 with item number:9 Orders are processed in the ers for today hariniramaprasad:~/workspace/ITS 6 1 solutions and_grading (master) Must always be printed at the end