From mboxrd@z Thu Jan  1 00:00:00 1970
From: Federico Beffa <beffa@ieee.org>
Subject: Re: reproducibility
Date: Wed, 13 Jan 2016 20:53:38 +0100
Message-ID: <CAKrPhPO9+9mGP9X0zDfzA6Ly_K37qVQxEdVp3-TZLkDku7AzdQ@mail.gmail.com>
References: <CAKrPhPP+j6jfmLFk5WuHxa6q=fRO++KHkeOZ4kC-Mnw8ZxNcSA@mail.gmail.com>
	<874mel2m94.fsf@gnu.org>
	<CAKrPhPMn_gQMyRoa8b8ZV=o8rovfUPTbVNQnR=PraLWgXuYq3Q@mail.gmail.com>
	<87bn8qa385.fsf@gnu.org>
	<CAKrPhPOLVB0O3uRCP=5-c5kYYdoRXknLO8uozy8cw==xtUeznw@mail.gmail.com>
	<87bn8p60rt.fsf@gnu.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Return-path: <guix-devel-bounces+gcggd-guix-devel=m.gmane.org@gnu.org>
Received: from eggs.gnu.org ([2001:4830:134:3::10]:57964)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <federico.beffa@gmail.com>) id 1aJRUB-0001xA-SB
	for guix-devel@gnu.org; Wed, 13 Jan 2016 14:53:40 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <federico.beffa@gmail.com>) id 1aJRUA-00045u-SU
	for guix-devel@gnu.org; Wed, 13 Jan 2016 14:53:39 -0500
In-Reply-To: <87bn8p60rt.fsf@gnu.org>
List-Id: "Development of GNU Guix and the GNU System distribution."
	<guix-devel.gnu.org>
List-Unsubscribe: <https://lists.gnu.org/mailman/options/guix-devel>,
	<mailto:guix-devel-request@gnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/archive/html/guix-devel>
List-Post: <mailto:guix-devel@gnu.org>
List-Help: <mailto:guix-devel-request@gnu.org?subject=help>
List-Subscribe: <https://lists.gnu.org/mailman/listinfo/guix-devel>,
	<mailto:guix-devel-request@gnu.org?subject=subscribe>
Errors-To: guix-devel-bounces+gcggd-guix-devel=m.gmane.org@gnu.org
Sender: guix-devel-bounces+gcggd-guix-devel=m.gmane.org@gnu.org
To: =?UTF-8?Q?Ludovic_Court=C3=A8s?= <ludo@gnu.org>
Cc: Guix-devel <guix-devel@gnu.org>

On Wed, Jan 13, 2016 at 2:56 PM, Ludovic Court=C3=A8s <ludo@gnu.org> wrote:
> Federico Beffa <beffa@ieee.org> skribis:
>
>> On Tue, Jan 12, 2016 at 10:37 PM, Ludovic Court=C3=A8s <ludo@gnu.org> wr=
ote:
>>> Federico Beffa <beffa@ieee.org> skribis:
>>>
>>>> On Sun, Jan 10, 2016 at 9:49 PM, Ludovic Court=C3=A8s <ludo@gnu.org> w=
rote:
>>>>> 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 t=
wo
>>>>>> 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.

I guess that's not necessary... I was just trying to learn something.

Thanks,
Fede