ARCHER2 MPI course (April 2024)

The world's largest supercomputers are used almost exclusively to run applications which are parallelised using Message Passing. The course covers all the basic knowledge required to write parallel programs using this programming model, and is directly applicable to almost every parallel computer architecture.

Parallel programming by definition involves co-operation between processors to solve a common task. The programmer has to define the tasks that will be executed by the processors, and also how these tasks are to synchronise and exchange data with one another. In the message-passing model the tasks are separate processes that communicate and synchronise by explicitly sending each other messages. All these parallel operations are performed via calls to some message-passing interface that is entirely responsible for interfacing with the physical communication network linking the actual processors together. This course uses the de facto standard for message passing, the Message Passing Interface (MPI). It covers point-to-point communication, non-blocking operations, derived datatypes, virtual topologies, collective communication and general design issues.

This course will be run over two days, slightly shortert than the normal three-day format, usinga variety of methods including formal lectures, practical exercises, programming examples and informal tutorial discussions. This enables lecture material to be supported by the tutored practical sessions in order to reinforce the key concepts.

Intended Learning Outcomes

On completion of this course students should be able to:

Understand the message-passing model in detail.
Implement standard message-passing algorithms in MPI.
Debug simple MPI codes.
Measure and comment on the performance of MPI codes.
Design and implement efficient parallel programs to solve regular-grid problems.

Pre-requisite Programming Languages:

C, C++ or Fortran. The course does not cover the details of how to use MPI from Python.

Message Passing Programming with MPI

Dates: 3rd - 4th April 2024

Location: West Hub, University of Cambridge

Timetable

Wednesday 3rd April

09:30 Message-Passing Concepts
10:15 Practical: Parallel Traffic Modelling
10:45 Break
11:15 MPI Programs
12:00 MPI Programs on ARCHER2
12:15 Practical: Hello World
12:30 Lunch
13:30 Point-to-Point Communication
14:15 Practical: Pi
15:00 Break
15:30 Communicators, Tags and Modes
16:15 Practical: Pi / Ping-Pong
17:00 Finish

Thursday 4th April

09:30 Pi Solution
10:00 Non-Blocking Communication
10:30 Practical: Message Round a Ring
10:45 Break
11:15 Practical: Message Round a Ring (cont)
12:00 Collective Communication
12:30 Lunch
13:30 Practical: Collective Communication
14:00 Overview of Virtual Topologies and Derived Data Types
14:45 Case Study
15:15 Finish Exercises / Individual Consultancy
16:00 Close

Lecture Slides

Unless otherwise indicated all material is Copyright © EPCC, The University of Edinburgh, and is only made available for private study.

Day 1

Day 2

Additional Material (not delivered as part of this course but included for reference)

Notes

MPI course notes (historical)

Exercise Material

Unless otherwise indicated all material is Copyright © EPCC, The University of Edinburgh, and is only made available for private study.

Installing MPI locally

Note that all registered users will be given access to the ARCHER2 system. Although having MPI installed on your laptop may be convenient, do not worry if these instructions do not work for you.

Linux

Linux users need to install the GNU compilers and a couple of MPI packages, e.g. for Ubuntu:

user@ubuntu$ sudo apt install gcc
user@ubuntu$ sudo apt install openmpi-bin
user@ubuntu$ sudo apt install libopenmpi-dev

Mac

Mac users need to install compilers from the Xcode developer package. It is easiest to install MPI using the Homebrew package manager - here are Instructions on how to install Xcode and Homebrew.

Now install OpenMPI:

user@mac$ brew install open-mpi

Windows

Rather than installing MPI locally, we recommend that Windows users access ARCHER2 using MobaXterm.

If you want to try local access to MPI, one solution is to install a Linux virtual machine (e.g. Ubuntu) and follow the Linux installation instructions above.

I know that some users have been able to install MPI compilers and libraries natively on Windows using the Intel® oneAPI HPC Toolkit

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