engineer

CSE3321.3

Assignment 2.

Using Threads.

Due Date: Wed. Nov. 15 4:00pm.

1. POSIX threads

In all the following questions include a short answer and on which man page you found

the information.

(1) What is the naming conventions for pthread function calls?

(2) Enumerate the synchronization mechanisms for POSIX threads?

(3) Why is it a good programming practice to call pthread_cond_wait from

within a loop?

(4) Which thread executes after a thread is woken up from a condition variable.

(5) What happens if a thread blocks on a condition variable while holding two

mutexes.

(6) What is a detached thread.

2. Probabilistic Analysis of Pthreads.

In this assignment you will write two pthreads programs that evaluate some aspects

of the pthreads system. The first and simpler of the two, lets threads write to the same file

using mutexes to avoid race conditions. The main thread creates N (N is an optional com-

mand line argument by dafault 100) threads and all of them immediately block on condi-

tion variable start_line. After all threads are created, the main thread wakes them up

and then waits until they all terminate with join. The threads after waking up lock the

mutex filemut and write their TID followed by newline to file pthread_stats and

then release the mutex. After they do this M times each (the second optional command

line argument that defaults to 1000) they join the main thread.

In the second pthread program of the assignment the main program creates N threads

designated as red and then another N threads designated as green. All of them imme-

diately block on condition variable start_line. After all threads are created, the main

thread wakes them up and then waits until the all terminate with join. The threads after

waking up lock the mutex filemut and write their TID followed by the word red or

green followed by newline to file pthread_stats. The difference in this second ver-

sion is that all the red threads write first their TID M times releasing and re-acquiring the

mutex, then all the green ones another M times, then the red threads again, and so on,

until they hav e alternated L (another optional command line argument that defaults to 10)

times each for a total 2×M×N×L lines in the file pthread_stats (or 2×M×L lines per thread).

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Both programs accept optional arguments. The first one is N, the second one is M

and the third one (applies only to the second program) is L.

To do the analysis write a small program in C, AWK, or python (I strongly recom-

mend AWK but python is also OK) to calculate the mean and standard deviation of the

“runs”. A run is the number of consecutive writes by the same thread.

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