Re: reproducibility

[ludo@gnu.org (Ludovic Courtès)]

Federico Beffa <beffa@ieee.org> skribis:

> On Tue, Jan 12, 2016 at 10:37 PM, Ludovic Courtès <ludo@gnu.org> wrote:
>> Federico Beffa <beffa@ieee.org> skribis:
>>
>>> On Sun, Jan 10, 2016 at 9:49 PM, Ludovic Courtès <ludo@gnu.org> wrote:
>>>> Federico Beffa <beffa@ieee.org> skribis:
>>>>
>>>>> I've noticed that a derivation is a function of the order of the
>>>>> inputs. As an example, the following two input orders give rise to two
>>>>> distinct derivations:
>>>>>
>>>>> A)
>>>>>
>>>>>     (inputs
>>>>>      `(("texlive" ,texlive)
>>>>>        ("texinfo" ,texinfo)
>>>>>        ("m4" ,m4)
>>>>>        ("libx11" ,libx11))
>>>>>
>>>>> B)
>>>>>     (inputs
>>>>>      `(("texinfo" ,texinfo)
>>>>>        ("texlive" ,texlive)
>>>>>        ("m4" ,m4)
>>>>>        ("libx11" ,libx11))
>>>>>
>>>>> Is this intentional?
>>>>
>>>> Yes.  There are several places where order matters, most importantly
>>>> search paths, and these are computed from the input lists.
>>>
>>> If order matters, it would probably be more robust to force internally
>>> a specific order rather than relying on the (often random) order
>>> defined in a package recipe (possibly created by an importer, ...).
>>
>> Most of the time any order would work, but I can imagine situations
>> where the packager could purposefully choose a specific order.  So I’d
>> rather not do any automatic sorting, if that’s what you have in mind.
>
> Just out of curiosity, could you provide a concrete example where the
> order is purposefully specified.

No specific example, sorry, but it’s plausible IMO.  With enough CPU
power, we could try rebuilding everything with a random order and see
what breaks.

Thanks,
Ludo’.