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Assignment 2

! No credit for a program that does not compile or does not run.
This assignment requires you to write a multi-threaded C program to carry out the matrix multiplication of two simple
integer matrices (2×4, and 4×2) as specified in the first assignment, and to display the results. The sixteen elements of
the two matrices are given at the command line. You are required to use the POSIX thread (pthread) library functions in
your program. Make sure that your submitted program compiles and runs in Athena. In addition, you need to compare
the multi-processed approach in the first assignment with the multi-threaded approach in this assignment and summarize
the differences in terms of the system overhead (process vs. thread creation and communication) and their pros and cons.
1. In your program, include the header <pthread.h> (see Pages 172-174 of the textbook). When compiling your
program, use a switch “-lpthread” to link pthread functions to your program.
2. The main thread in the program takes the input data of sixteen integer values from the command line and verifies for
correctness. If the number of input is not correct, or any of the input data is not an integer (e.g., abc, −34a5), the
main thread prompts the user with the message: “Incorrect number of input or incorrect type of input” and then
exits. Signed integers should be allowed. You can reuse the input validation logic. The order in which input data are
used in initializing matrices A and B is the same as in Assignment 1.
3. After reading the correct input data, the main thread then creates (pthread_create) five threads out of five
functions of MC0, MC1, MC2, MC3 and Display. MC0 through MC3 calculate c0 through c3, respectively, in the
resulting matrix C. After finishing their calculations, MC0 through MC3 communicate their respective results
independently to the thread Display that displays the resulting matrix C using printf in the same manner as in the
previous assignment. All threads will exit after finishing their tasks (pthread_exit).
pthread_t myThread1;
pthread_create(&myThread1, NULL, (void *) MC0, NULL);
4. The communication between MC0 and Display, …, and between MC3 and Display is now facilitated through the use
of some shared variables in the process. If a need arises to maintain the integrity of a shared variable, a lock
mechanism called mutex lock and its functions can be used in the following manner:
pthread_mutex_t myLock1 = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_lock(&myLock1);
x = ……;
pthread_mutex_unlock(&myLock1);
5. The main thread will wait until after all five threads finish their tasks (pthread_join), then it exits. Arrange
some messages (via printf) from all threads before they exit. For the main thread, display a message before each
thread is created, a message before issuing pthread_join calls to start the waiting stage, and a message before it
exits. For each of the remaining threads, display a message including its tid (pthread_self()) right after being
created, a message for its result (computation or communication results), and a message before its termination
(pthread_exit).
6. Submission Requirements. Your program must include adequate commenting (points deduction for programs
with inadequate comments). Compile your program using the following:
gcc prog2.c -o prog2 -lpthread
CSC 139, Spring 2015
Department of Computer Science, CSUS
2/19/2015
a) Test your program to make sure it works correctly for at least the following four scenarios. Submit your source
file to Assignment2 in SacCT.
Prog2 ……//incorrect number of input, say, 10 or 17 integers.
Prog2 ……//incorrect type of input, say, -3a4 in command line.
Prog2 ……//16 integers, say, 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Prog2 ……//16 integers, say, -16 +15 14 13 -12 -11 +10 -9 +8 +7 6 +5 4 3 2 1
b) Compare the multi-processed approach with the multi-threaded approach (the system overhead in process/thread
creation and communication, and their pros and cons). Submit your comparison in a .txt file to Assignment2 in
SacCT as well.