L3 & L4

Question 1

True or False:

The threads in the same process share a different address space.

Answer 1

False.

They share the same address space.

Question 2

A program runs on a CPU as a ______.

Answer 2

process

Question 3

How do threads communicate?

Answer 3

shared memory

Question 4

What are some ways to program threads?

Answer 4

Pthread library (C/C++/Fortran)
Java threads

Question 5

What return value indicates a success for pthreads?

Answer 5

0

Question 6

What is used in pthread to:
a. create a thread
b. exit a thread
c. wait for a thread to finish

Answer 6

a. pthread_create()
b. pthread_exit()
c. pthread_join()

Question 7

How can the order of thread execution be controlled?

Answer 7

Synchronisation

Question 8

What is the difference between implicit and explicit parallelism?

Answer 8

Explicit parallelism: programmer explicitly spells out what should be parallelized (ex: OpenMP)

Implicit parallelism: the system works out parallelism by itself without the programmer modifying the program

Question 9

Why is automatic parallelisation difficult?

Answer 9

because dependency analysis is hard

Question 10

If threads do not share memory, how is communication done?

Answer 10

via message passing

Question 11

What is the cache coherency problem in multiprocessors?

Answer 11

Challenge of maintaining consistency and avoiding data inconsistencies when multiple processors or cores share a common memory and have their own caches.