Supercomputing with Raspberry Pi | HackSpace 41

Although it’s a very flexible term, supercomputing generally refers to the idea of running multiple computers as one, dividing up the work between them so that they process in parallel.

In theory, every time you double the amount of processing power available, you half the time needed to complete your task. This concept of ‘clusters’ of computers has been implemented heavily in large data processing operations, including intensive graphics work such as Pixar’s famous ‘render farm’. Normally the domain of large organisations, supercomputing is now in the hands of the masses in the form of education projects and makes from the cluster-curious, but there have also been some impressive real-world applications. Here, we’ll look at some amazing projects and get you started on your own supercomputing adventure.

OctaPi

One of the first high-profile cluster projects surprisingly came from the boffins at GCHQ (Government Communications Headquarters) in the UK. Created as part of their educational outreach programme, the OctaPi used eight Raspberry Pi 3B computers to create a cluster. Kits were loaned out to schools with multiple coding projects to engage young minds. The first demonstrated how supercomputing could speed up difficult equations by calculating pi. A more advanced, and very appropriate, task showed how these eight machines could work together to crack a wartime Enigma code in a fraction of the time it would have taken Bletchley Park.

Turing Pi

As we’ve already said, most Raspberry Pi cluster projects are for education or fun, but there are those who take it seriously. The Raspberry Pi Compute Module form factor is perfect for building industrial-grade supercomputers, and that’s exactly what Turing Pi has done. Their custom Turing Pi 1 PCB can accept up to seven Raspberry Pi 3+ Compute Modules and takes care of networking, power, and USB connectivity. Although claiming a wide range of uses, it appears to have found a niche in the Kubernetes world, being a surprisingly powerful device for its price. Future plans have been announced for the Turing Pi 2, based on the more powerful Raspberry Pi 4.

Water-Cooled Cluster

Multiple machines are one thing, but there’s also the individual speed of those machines. The faster they go, the faster the cluster operates exponentially. Overclocking is common in supercomputing, and that means heat. This water-cooled cluster, which maker Michael Klements freely admits is one of those ‘just because’ undertakings, uses the kind of water cooling usually found on high-end gaming PCs and applies it to a Raspberry Pi cluster. This beautiful build, complete with laser-cut mounts and elegant wiring, has been extensively documented by Klements in his blog posts. We can’t wait to see what he does with it!

Oracle Supercomputer

So how far can we take this? Who has built the largest Raspberry Pi cluster? A strong contender seems to be Oracle, who showed off their efforts at Oracle OpenWorld in 2019. No fewer than 1060 Raspberry Pi 3B+ computers were used in its construction (that’s 4240 cores). Why 1060? That’s as much as they could physically fit in the frame! The creation has no particular purpose bar a demonstration of what is possible in a small space, cramming in several network switches, arrays of USB power supplies, and a NAS (network-attached storage) for boot images.

Make your own

We’re thinking you probably don’t fancy trying to beat Oracle’s record on your first attempt, and would like to start with something a bit simpler. Our sister magazine, The MagPi, has published a cluster project you can make at home with any number of Raspberry Pi devices (although just one might be a little pointless). In this case, four Raspberry Pi 4B computers were assigned the job of searching for prime numbers. Each is assigned a different starting number, and then each adds four before testing again. This is handled by an open-source cluster manager, MPI (Message Passing Interface). A solid introduction to what is possible.

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Each month, HackSpace magazine brings you the best projects, tips, tricks and tutorials from the makersphere. You can get it from the Raspberry Pi Press online store or your local newsagents. As always, every issue is free to download from the HackSpace magazine website.