An ambitious attempt to build a makeshift supercomputer from hundreds of random laptops has missed its target of breaking into the list of the world鈥檚 top 500 fastest machines.
More than 700 volunteers gathered at the University of San Francisco on Saturday to build the 鈥渇lash mob supercomputer鈥� using their own laptops. But many of the volunteered computers were simply too unreliable for the whole system to run 鈥渋n parallel鈥� for long enough to reach top speed.
Each computer was connected to a local area network (LAN) and had software installed to enable it to perform challenging mathematical calculations by coordinating with the other laptops.
Advertisement
The resulting machine, dubbed FlashMob, would have needed to perform a rigorous benchmark calculation called Linpack at a rate of at least 403 billion flops (floating point operations per second) to be ranked as one of the top 500 supercomputers. But FlashMob only reached a relatively modest peak performance of 180 billion flops.
Unstable behaviour
From more than 700 computers brought to the event, only 669 could be connected to the network properly. But even these suffered difficulties.
The key problem was that many of the laptops malfunctioned during FlashMob鈥檚 calculations. As a result, the peak performance was reached by combining the power of only 256 computers. Even this cluster proved too unstable to complete the Linpack calculation. The best completed result was 77 billion flops using just 150 computers.
鈥淭he biggest challenge was identifying flakey computers and determining the best configuration for running the benchmark,鈥� writes John Witchel, the USF graduate student organising the project, on its homepage.
Unknown capability
Prior to the gathering, Witchel admitted that that not knowing the capabilities of the computers involved until they arrived could be a problem.
Even getting FlashMob to 180 billion flops required Witchel to write some clever software. Many ordinary supercomputers are constructed by connecting relatively cheap servers or desktop computers together, but these normally use ultra-fast networking equipment to keep each machine synchronised with the rest.
Each processor鈥檚 memory must be 鈥渢ightly coupled鈥� so that it can update itself continuously while keeping track of its peers鈥� calculations.
In contrast, the laptops in FlashMob were linked via an ordinary LAN. The LANs used in offices and homes allow computers to share saved files of about three megabytes in size. But a supercomputer requires processors to share hundreds of megabytes a second, which is what Witchel鈥檚 software helped FlashMob to do.