Models & Tools for Parallelism

Home| Course

Foreword

The following exercises needs for you to access a Unix system. A Linux operating system would be better (because I didn't try these exercises on Solaris) but probably not mandatory.

1. Hello World

• Read the man pages for pthread_create.
• Copy the following program, compile it (don't forget the -lpthreads flag in the compiler options), understand it and make it work:

  #include <pthread.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include 
  #include 
  #include 
  
  void *hello() {
    printf("Hello World!\n");
    pthread_exit(NULL);
  }
  
  int main() {
    pthread_t thread;
  
    if (pthread_create(&thread, NULL, hello, (void *) NULL) == -1) {
       perror("hellothread");
       exit(1);
    }
  
    exit(0);
  }
  

2. pthread_join

Write a program that creates two threads in one Unix process. One of the threads should execute the following for-loop:

for(i=0; i<21; i++) 
  printf("The square of %d is ", i);

The other thread should execute the following for-loop:

for(i=0; i<21; i++)
  printf("%d\n", i*i);

The main thread should wait for the two threads to finish (pthread_join) and finally print:

printf("That's all!\n");

3. Threads vs. Processes

• Make a program that create a certain number of threads.
• Make a program that fork the same amount of time.
• With gcov, evaluate the time spend on process creation and on threads creation..