Developing a good bedside manner

September 23, 2009

Jack Ganssle-September 23, 2009

Why are debugging code and alien abduction so similar? Because in both cases large blocks of time are unaccounted for.

Medicine, too, resembles debugging (and perhaps alien abduction). In an astonishing development, recently my doctor actually chatted with me for a few minutes. Maybe it was a slow H1N1 day, or perhaps he just wanted a break from all of the runny noses. So I asked him what the hardest part of his job was. Expecting to hear a rant against insurance companies, it was interesting to hear him talk about the difficulty in diagnosing diseases. Most people present with simple cases, but sometimes an individual will have a bewildering array of symptoms that suggest no single etiology. Physicians use differential diagnosis to try and weed causation from the complaints, which is made very complex since patients may ignore some important symptoms while focusing on those that are less critical. To add spice to the sauce of diagnosis, several illnesses may present at the same time.

I was struck by how closely his comments mirror the art of debugging embedded systems. Our nascent product has a bug, which presents itself via some set of symptoms. Press the green button and nothing happens. Is the switch wired incorrectly? Could its Schmidt trigger gate be shot? Is the ISR invoked? Perhaps the ISR never passes a signal to the code that displays a result.

Or maybe the power is off.

In other cases, just as in medicine, one bug may present a variety of odd effects. Or a single symptom could stem from a combination of bugs all interacting in excruciating-complex, and hard to diagnose, manners. I wonder if physicians observe the infrequent symptoms we see, that appear in a system once, go away for weeks, and then randomly resurface?

Then there are the bugs we know exist, but just cannot fix. The system gets shipped with the expectation that sometime someone will see a problem. That, too, is like medicine. "Doc, it hurts when I do this." "Don't do that." My health insurance will not cover kidney stones due to three prior episodes, one of which required an expensive lithotripsy. So that's one latent bug in my gut that will surely reappear at some unknown time in the future.

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