Description
1. Condition Variables
The program file condvar-pthd.c is an incomplete Pthreads program. The main() routine creates two
threads, one sender and one receiver. Complete the program by providing code for these two threads, so
that the sender will send a signal, and the receiver will wait for the signal.
The sleep(1) call in sender() is to help to see the waiting. When you run the completed program, you
should see two message lines first:
Sender starts …
Receiver starts …
After a pause, you should see the third line:
Signal received!
2. Array Sum
The program file arraysum-pthd.c is a simple Pthreads program for computing array sum. (We’ve shown
this program in class.) Use an editor to open the file; read and understand the program; and then compile
and run it:
linux> make arraysum-pthd
linux> ./arraysum-pthd
…
The sum of 1 to 1000 is 500500
Exercise 1 In class, we showed additional versions for this program. Your task is to create and run these
versions. Specifically,
1. Modify the printf statement to also print out the CPU id, along with the thread id.
2. Insert the CPU-affinity code shown in class to the program, so that thread k is assigned to run on
CPU k. (If there are more threads than CPUs, then follow a round robin assignment.)
3. Add command-line arguments for arraySize and numThreads configurations.
Note that you need to change the inclusion headers accordingly for each step. You may want to stop and
test the program after each step.
Exercise 2 Assume you have a working version of the modified program. Comment out all the locking
and unlocking statements in the program; and re-compile it. Now, this program has the potential for race
conditions. Run the program with different arraySize and numThreads configurations until you see an
evidence of a race condition occurring. Write down the array size, the number of threads, and the evidence.
3. New Pthreads Programs
The program file mtxmul.c contains a simple sequential implementation of matrix multiplication. Use an
editor to open the file; read and understand the program; and then compile and run it.
1
1. Convert mtxmul.c into a Pthreads program, mtxmul-pthd.c. Use N threads, one for each iteration
of the i loop. Compile and test your program.
2. Write a second version of the Pthreads program, mtxmul2-pthd.c. In this version, the number
of threads is not fixed. The program reads in an optional command-line argument representing the
number of threads. If the argument is not provided, the program use the default value of N. For
example,
linux> ./mtxmul2-pthd 4 // using 4 threads
linux> ./mtxmul2-pthd // using the default of N threads
Use a simple partitioning scheme to partition the workload for the threads.
2