Great question. I have a friend who used to work on the human brain project and I asked him a similar question. What surprised me is that the software that gets

Great question. I have a friend who used to work on the human brain project and I asked him a similar question. What surprised me is that the software that gets run on super computers is usually quite simple BUT the computational complexity is high or the volume of data is large. Fairly non-technical people (i.e. not necessarily computer scientists but maybe mathematicians) would typically submit small programs written in Python that would be automatically compiled into something that used the hardware to its maximum potential (instead of compiling it to something more portable). I believe that software running on super computers is closer to the wire than clustered computers. The operating systems are often very stripped down and custom too.