Computer Science 335
Parallel Processing and High Performance Computing

Fall 2024, Siena College

Home     Syllabus     Schedule     Examples

In this lab, you will learn about collective communication using MPI. Until now, we have used only point-to-point communication, i.e., sends and receives.

You may work alone or with a partner on this lab.

Learning goals:

1. To learn the basics of collective communication in MPI.

Getting Set Up

In Canvas, you will find a link to follow to set up your GitHub repository, which will be named coll-lab-yourgitname, for this lab. Only one member of the group should follow the link to set up the repository on GitHub, then others should request a link to be granted write access.

You may choose to answer the lab questions in the README.md file in the top-level directory of your repository, or upload a document with your responses to your repository, or add a link to a shared document containing your responses to the README.md file.

Reading

Read Pacheco Ch. 3, Section 4, to learn about MPI's collective communication capabilities.

Collective Communication

In addition to the example mpi_trap3.c from the text chapter, there are two examples to consider in the repository for this lab: mpicoll.c and mpiscatgath.c.

For the first task, worth 20 points total, instead of writing answers in your response document, you will open GitHub Issues and provide your answers there. This process will be demonstrated in class.

For each line or group of adjacent lines that uses MPI collective communication calls in mpi_trap3.c, mpicoll.c, and mpiscatgath.c:

• if it is the first example of this collective communication function, briefly describe its effect in general terms,
• describe what it is doing specifically in this case, and
• describe what data exists on each process before and after the call.

Submission

Make sure your answers to lab questions are provided using one of the mechanisms mentioned in the "Getting Set Up" part of the lab, and that your responses to the first part are in GitHub Issues in your repository.

Grading

This assignment will be graded out of 35 points.