Question

1) Producer/Consumer again
Consider the bounded buffer Producer/Consumer problem we discussed in class. Assume the buffer size is now 10. Assume the Producer process enters 3 items at a time into the buffer. It will only do this if there are at least 3 empty spots in the buffer. Assume the Consumer process will remove items two at a time, and will only do so if there are at least two items in the buffer. In addition to the Producer and Consumer processes, assume there is a third Hybrid process. Each time it accesses the buffer its role changes. One time it is a Producer entering a single item, and the next time it is a Consumer removing a single item. Write pseudocode for these three processes using semaphores, counters, etc. to handle this situation.

Answer 1

int Buffer_size=10;
mutex=1;
empty=10;
full=0;
Solution for Producer process:
do{

//produce three items for inserting into buffer

wait(empty>=3);  //checks whether empty spots are atleast 3
wait(mutex);   //applys lock incase of empty 

//place in buffer 

signal(mutex);  //releases lock.
signal(full+3);  //increases the number of filled spots by 3.

}while(true)

Solution for Consumer problem:

do{

wait(full>=2);  //checks whether atleast two spots are filled in buffer.
wait(mutex);    //applys lock incase of available filled spots.

// remove 2 items from buffer

signal(mutex);   //releases lock.
signal(empty+2);  //increases the number of empty spots by 2.

// consume 2 items

}while(true)

Solution for Hybrid process:

int i=1;

do{

if(i%2!=0) //producer process at even times.

{

//produce an item

wait(empty); //checks for an empty spot

wait(mutex); //applys lock if any empty spot.

//place in buffer

signal(mutex); //releases lock

signal(full); //increases full by 1

i++;

}

if(i%2==0)

{

//consumer process at even times.

wait(full); //checks for filled spot.
wait(mutex); //applys lock.

// remove item from buffer

signal(mutex); //releases lock.
signal(empty); //increases empty spots by 1.

// consumes item

}

}while(true)

Hope this helps you..

Feel free to comment ,incase of any doubts :)