[Users] Prologation=NaN

Ian Hinder ian.hinder at aei.mpg.de
Thu Sep 17 15:24:03 CDT 2015

On 17 Sep 2015, at 21:12, Erik Schnetter <schnetter at cct.lsu.edu> wrote:

> That's a clever idea. We should implement this.
> No, it doesn't exist yet.

I agree - this is a very nice idea.

One of my favourite rants is this:

Don't use NaN for poison!  If you do, then you cannot tell the difference between NaNs generated because of numerical problems, and poison generated due to programming bugs.  These are really two different classes of problem, and it is very useful to be able to tell them apart.   Instead of NaN, you can use a specific floating-point value, such as 10^200, or something that is obviously not a correct part of the simulation (you would have to be extremely unlucky, 1 in 2^64) to numerically-generate the exact floating point value that you chose, assuming it is large) .  If you see that value in the simulation, then you are seeing poison, and it's a programming error.  If you see NaN, it's a numerical problem.

Ian Hinder

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