OT: tolerance was Re: Testing

[James Browning]

On Mon, Jul 15, 2019, 5:15 PM Hal Murray via devel <devel at ntpsec.org> wrote:

>
> tenterline at gmail.com said:
> > I come from a scientific background, where we compare results somewhat as
> > analog values. If the test result is off the expected by 1000%, that's
> bad.
> > If it's off 1%, better. If the error is .00001%, probably within
> achievable
> > accuracy.
>
> There is a difference between running the same experiment again to get new
> data and running new software on old data.
>
> Are the specs and implementation for IEEE floating point tight enough so
> that
> I should get the exact same result if I run a test on a different CPU
> chip?
> Or is there room for things like holding extra bits in temporary results
> so
> the bottom bits might be different due to round off or such?
>

Possibly. But I would say have a tight tolerance and a not so tight one. If
the absolute difference is less than both paint it green, if only one then
yellow, and for neither red. I'm probably wrong though.

>
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