Anything worth doing, is worth doing right.

I’m pretty sure that I invented the term “viewgraph norm”. It isn’t a pretty story since the invention of the term came in a fit of frustration and disgust at a co-worker, but history doesn’t have to be pretty. The viewgraph norm is the modern compliment to the “eyeball norm”. Comparing results in the eyeball norm is not precise and doesn’t constsodanitute proof, it’s a rough check. Sometimes it is offered as evidence because the author doesn’t want to look to close either because they are lazy, or they know that the result won’t bear up under scrutiny.

It was back in 1997 or 1998 and I was working in Los Alamos’ Applied Theoretical Physics Division (i.e., the infamous X-Division). Every week or two we’d have a “work in progress” seminar given by one of the staff on an ongoing project. One of these talks was on comparing the solution on a number of standard test problems for shock physics. The talk looked at a number of the available computer codes on a number of test problems with analytical solutions. As the talk proceeded, it became crystal clear that the analytical solution would be used only for plotting.

The talk was simply a series of plots comparing the code solution to the plot of the analytical. The message was clear, everything is fine, and all the codes converge to the analytical. Never once was an actual numerical error computed, or convergence actually checked. I became disgusted and increasingly agitated because I knew the truth was far different, many, if not most of the codes were not convergent to the analytical solution because I had been running the same problems with the same codes.

Finally near the end of the hour and finding myself utterly revolted by the whole talk, I stormed out and exclaimed, “It converges in the viewgraph norm!”

The term lived on, and other used it to call out charlatans employing the same sort of proof in their talks, with comments like “nice viewgraph norm!” Over time, I developed a sort of metric for the actual quality of a viewgraph norm. The better a result afig6ctually is, the longer the speaker will leave the viewgraph up to be examined. If the result is poor, the viewgraph won’t be available for examination for more than a few seconds.

It also turns out that when it comes to shock tube solutions, the viewgraph norm is the standard. No one even today publishes the error magnitudes with solutions even though it is trivial, and the differences between methods (or codes) is quite substantial.

Do ordinary things extraordinarily well.

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