Yup, getting the the problem to fit the machine was hard. I thought NCUBE was better than the CM1 for doing actual work.
Some people resorted to just running each node separately, after the initial conditions were set up there was no need for communications. That was one way around having to be clever and adapt your algorithm. They would run for days, sometimes because nobody else was on the machines :)
At one point I got my 2D code running on a CM2 (IIRC), one of the nodes was bad and the Fortran log function always returned 0. So when I made the movie of my simulation there was one tile/rectangle that was just blank. Afterwards they asked me if they could use my program as a diagnostic tool to verify all the nodes were working correctly. :))
I moved one from parallel and supercomputers when I graduated. Don't miss them that much.
It is interesting you mention the log function being what tripped up the broken node. On the CM1 and CM2, log was implemented via Feynman's algorithm for logarithms, which finds factors via a shift and subtract and then adds precomputed logarithms of them via a hit to a table that is shared by all the processors. If one of the nodes had a bad route to that lookup table (however that was actually done), it would result in just that node failing to return a result for a log instruction.
Some people resorted to just running each node separately, after the initial conditions were set up there was no need for communications. That was one way around having to be clever and adapt your algorithm. They would run for days, sometimes because nobody else was on the machines :)
At one point I got my 2D code running on a CM2 (IIRC), one of the nodes was bad and the Fortran log function always returned 0. So when I made the movie of my simulation there was one tile/rectangle that was just blank. Afterwards they asked me if they could use my program as a diagnostic tool to verify all the nodes were working correctly. :))
I moved one from parallel and supercomputers when I graduated. Don't miss them that much.