Principles of Parallel Programming - Chapter One

Threads in C

A gentle introduction

The first example is thread_101_1.c. This program exhibits how interact with pthread methods such as pthread_create and pthread_join.

In order to compile the program run the following command gcc -pthread thread_101_1.c -o thread_101_1

The thread_exit.c function

The code thread_exit.c uses some compilation directives in order to show how the use or lack of use of some functions calls affect the performance of a threads-based program.

The thread_exit.c can be compiled through the make command as follows:

• make te-00 this is a normal compilation of the code.
• make te-01 enables that during PrintHello() execution the sleep() function being called
• make te-02 avoids that main() thread invokes pthread_exit()

This code has been taken from https://computing.llnl.gov/tutorials/pthreads/#CreatingThreads

Passing arguments

As follows two examples about passing arguments to a new created thread are shown:

• hello_arg1.c In this example a variable of a basic type is passed as argument

• hello_arg2.c In this example a variable of a user defined type is passed as argument

Those codes were taken from this site:

• hello_arg1.c

• hello_arg2.c

Examples of collaborative work

Scalar product

For this problem two solutions are presented:

• mpithreads_serial.c a serial version

• mpithreads_threads.c a thread-based version

This code has been taken from https://computing.llnl.gov/tutorials/pthreads/exercise.html

Description of 3s-0*.c

Those programs, having 3s-0 as prefix, are implementations of an example described in chapter one of the Principles of Parallel Programming book. Please open each program and follow the instructions there.

Final assignment

• To implement the Fourth Solution: Try 4 found in page 20 and compare the performance of your implementation with previous programs.

• To identify a computationally intensive problem. Some trivial examples

  • To calculate Fibonnaci's number of every numer in an array of 100,000 positions. Each position has a value less or equal to 30. Be assure your Fibonacci's implementation is recursive.
  • To calculate the area under the curve following the Riemann's approach.
  • To calculate Pi value following the Monte Carlo's approach.

• Show a graph where your program's behaviour is depicted. Axis X would represent the number of threads in your execution and Axis Y represents the execution time.