Re: Suggestion needed on test failures due to double arithmetics

Hi Paul,

On Thu, Nov 25, 2021 at 3:24 AM Paul Wise <pabs@debian.org> wrote:
> Giulio Paci wrote:
>
> > 3) what is the most appropriate solution.
>
> As I understand it, floating point values should not be compared
> without some kind of accuracy/precision factor. Zero idea about the
> best reference for how to do it correctly, but here is a random one:
>
> https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/

Thanks for this link.
It is a very great resource and summarizes very well what I already
know about double/float and much more.

Since the test case is dealing with timings, I think the most related
article is [1].
However even after reading that article it seems to me that in this
case it should be reasonable to expect stable behavior of those
operators.

I have uploaded simplified code that showcase the issue and some of
the instabilities [2]. The code seems to behave as if the last value
is different from the other 3, supposed equal values.
I am not even sure what I am seeing in the debugger, since most of the
values are optimized out (and I am not so skilled with debuggers).

[1] https://randomascii.wordpress.com/2012/02/13/dont-store-that-in-a-float/
[2] https://pastebin.com/embed_js/T3g560UV

Bests,
Giulio

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