| > The non-determinism that page talks about is coming from bugs like memory corruptions, ..., initialisation order bugs. Source? I haven't seen these specifically cited anywhere. > floating point inaccuracies, Combined with (safe) race conditions, this will cause non-determinism that would probably be considered OK. In general: John Carmack looked at the code and thought it was OK for what it is (decade old simulation transpiled from Fortran at some point). Some ex-Google guy thinks its horrible. I looked at the code myself briefly. I haven't formed a strong opinion about the code myself beyond "it's ugly and I don't want to work with it, glad it's not my problem." I am however objecting to some of the comments here that make it sound like it is obviously broken for reasons that they just don't understand. I think a comment on the GitHub is relevant: https://github.com/mrc-ide/covid-sim/issues/175#issuecomment... > To add to this, please read report 9 properly. The 500k UK prediction was if governments did nothing whatsoever - we never believed governments would do nothing but we modelled it as a base case, because that's part of what you do when you model. > With the full social distancing the report suggestd it might be possible to reduce deaths perhaps to 20k - a death count we have already exceeded. Nobody here is laughing about that. The report was also very frank about the uncertainty involved in trying to predict what might happen at that stage |