Mounted on a clear acrylic plate, twelve Raspberry Pi boards suddenly spring into life, moving outwards, as if waving to the attendees at Maker Faire Miami. Not just a cool effect, the movement is proportional to each Raspberry Pi’s level of activity in a parallel computing cluster. This is Raspberry Pi VizuWall, a project created by long-time computer engineer Matt Trask during his degree course at Florida Atlantic University (FAU), while doing research into a new class of supercomputer systems.

“When I am successful (heh, nearly said ‘if’ there…), it will obsolete MPI [Message Passing Interface] as the main means of programming distributed compute clusters,” explains Matt. “This means that my variant of the Beowulf architecture will function as a distributed symmetric multiprocessing system that appears to be a single unified system that is the sum of all RAM and all cores in the cluster: a virtual mainframe computer. Perhaps the solution to the so-called Ninja Gap?”

Matt is referring to the difficulty of enabling computer science students to obtain enough early experience programming parallel computing systems to become industry-proficient. Hence his motivation for building a low-cost cluster system with Raspberry Pi boards, in order to drive down the entry-level costs.

Raspberry Pi VisuWall: Quick Facts

This prototype was created to justify the cost of building a much larger version

PoE will be used to simply power distribution in the next iteration

Matt has been a computer engineer for nearly 40 years

He wrote the first virtual machine software on the 80386 processor in 1986

He got his first Raspberry Pi in 2012

VisuWall Moving parts

Matt reveals how Raspberry Pi VizuWall works: “Each node is capable of moving through about 90 degrees under software control because a small electric servo motor is embedded in the hinging mechanism. The acrylic parts are laser-cut, and the hinge parts have been 3D-printed for this prototype.”

While the original concept was to also use LEDs to edge-light the acrylic plate and change the colours to indicate CPU usage, Matt says the idea of the moving boards was always fundamental to the project: “I figured that the physical motion would help student programmers understand their system utilisation. And it looks cool.”

Although Matt came up with the project’s concept several years ago, he only started building it in late 2018. “I collaborated with Art Rozenbaum (FAU Mechanical Engineer) over the fall to develop the concept and submitted my research proposal in November,” he tells us. “Art and I worked through my original concept for mounting the servos behind the board and pivoted to his concept of embedding them in the hinge mechanism, a much cleaner solution.”

Currently, the Raspberry Pi boards have wired communication via a 14-port Ethernet switch, but Matt is looking into making it wireless. This will involve “evaluating whether the Pi’s wireless LAN capability is suitable for carrying the MPI message traffic, given that the wired Ethernet has greater bandwidth.”

Scale model

The original plan for Raspberry Pi VizuWall was to create a 4×8 ft (1.2×2.4 m) wall with 300 Raspberry Pi boards wired as a Beowulf cluster running the MPICH implementation of MPI. “When I proposed this project to my Lab Directors at the university, they baulked at the estimated cost of $20–25,000 and suggested a scaled-down prototype first.”

Matt says some lessons have been learnt in the process of building it, including plans to replace the 3D-printed plastic motor housings – which suffered minor distortion due to heat from the servos – with CNCed aluminium. “This will [also] permit us to have finer resolution when creating the splines that engage with the shaft of the servo motor, solving the problem of occasional slippage under load that we have seen with this version.”

The ultimate goal is to “create a massive piece of kinetic art to embellish the entryway to our new Lab facility at the university.”