Computer model that locked down the world turns out to be sh*tcode

John Carmack replies https://twitter.com/ID_AA_Carmack/status/1258192136744456199:

> It is disappointing, but not really unexpected, to see this take on the epidemic simulation code release: https://lockdownsceptics.org/code-review-of-fergusons-model/ If we accept it at face value, we have a retired software engineer making the case that non-determinism in a simulation shows incompetence. I am all for deterministic-everything, but issues with random seeds and parallel floating point reductions are extremely widespread, and a great deal of science gets done with non-deterministic simulations. Heck, professional software engineering struggles mightily with just making completely reproducable builds. I take no position on the mechanics of the simulation or the conclusions drawn from the runs, but implicitly encouraging scientists to keep their code secret if it isn't "perfect" is damaging.

Also later:

> There was a continuous integration regression test running a small model in single threaded mode on every check in, comparing for exact accuracy, at least when I was working on it -- I haven't pulled the public release.

For background, he was pulled in to do a bit of work on the simulation code a month or two ago.

Yeah lets not forget this either: https://twitter.com/neil_ferguson/status/1241835454707699713

"I’m conscious that lots of people would like to see and run the pandemic simulation code we are using to model control measures against COVID-19. To explain the background - I wrote the code (thousands of lines of undocumented C) 13+ years ago to model flu pandemics..."

(the whole thread is interesting)

Intermittently down, but points to https://lockdownsceptics.org/code-review-of-fergusons-model/

> Edinburgh reported the bug to Imperial, who dismissed it as “a small non-determinism” and told them the problem goes away if you run the code on a single CPU (which the reviewer notes “is as far away from supercomputing as one can get”).

Makes you wonder about the priorities of the reviewers.