A punch card, what I used when I first began writing
I'm running a simulation, creating a set of miniature universes, designed to let me explore what happens if I staged their creation over and over again. Ten thousand times in this case.
The mathematical model behind it all is called the Monte Carlo method, enabling my universes to evolve by a combination of rules and random chance. Though I usually use these methods on chemical systems, this time I'm modeling a social system.
I've been working on the code off and on over the last week, and this afternoon had it in shape to run some quick models to make sure the code was working. Once I was sure (or as sure as you can be) that the code had no significant bugs, I put a 30 minute simulation on to run and went for my walk. The results were encouraging, so I started a longer run, then went to have dinner.
It reminded me of graduate school days, when I would put a job on to run while I went home for dinner, then go back to the lab to get my results and queue something up for an overnight run. Yes, these were the days before machines were webbed into each other, no way to call in and get the results from much further away than the little room in the Physical Sciences building that had no windows and several terminals, wired into our research group's Harris computer (see a photo of one here, the large boxes on the left are the computers, the washing machine sizes things on the right are hard drives, 40 MB — not GB, MB — hard drives; our large drive was 80 MB).
When I was in graduate school, I could track my jobs by ear, the disks would begin to scream when the jobs hit a particular point in the code that was I/O intensive, either trying to stash the values of integrals as fast as they possibly could, or peeling them back to reassemble into a final value. My silent solid state drive offered me no such clues to progress, so even though I know that it slowed my code down a tiny bit, I inserted a counter, so I could see what it was up to. The eight thousandth ninety-first universe, when I began writing this.