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From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: reproducibility
Date: Wed, 13 Jan 2016 14:56:38 +0100
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	(Federico Beffa's message of "Wed, 13 Jan 2016 09:13:25 +0100")
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To: Federico Beffa <beffa@ieee.org>
Cc: Guix-devel <guix-devel@gnu.org>

Federico Beffa <beffa@ieee.org> skribis:

> On Tue, Jan 12, 2016 at 10:37 PM, Ludovic Court=C3=A8s <ludo@gnu.org> wro=
te:
>> Federico Beffa <beffa@ieee.org> skribis:
>>
>>> On Sun, Jan 10, 2016 at 9:49 PM, Ludovic Court=C3=A8s <ludo@gnu.org> wr=
ote:
>>>> 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=E2=
=80=99d
>> rather not do any automatic sorting, if that=E2=80=99s 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=E2=80=99s plausible IMO.  With enough CPU
power, we could try rebuilding everything with a random order and see
what breaks.

Thanks,
Ludo=E2=80=99.