As a learning tool, this is really cool. For practical compute workloads, it's not very interesting. A Cortex-A7 core @ 900MHz has a peak of 1.8 Gflops (singl

As a learning tool, this is really cool. For practical compute workloads, it's not very interesting. A Cortex-A7 core @ 900MHz has a peak of 1.8 Gflops (single-precision; 450 Mflops for double). Assuming that you could actually achieve peak for the cluster as a whole (you can't for non-trivial problems because of communication overhead), that would give you 43 Gflops in single precision and 10.8 Gflops in double. A single Haswell core clocked at a very conservative 2 GHz has a peak of 64 Gflops in single-precision and 32 Gflops in double, without communication overhead because it's a single core. More importantly, the Cortex-A7 is a 32-bit machine, so working on big problems is painful (though it does support LPAE). There's also much better availability of highly-tuned compute libraries for x86 and GPUs. You're going to be writing your own compute kernels to get near peak on the cluster of Cortex-A7.