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From: "Ludovic Courtès" <ludo@gnu.org>
To: ilmu <ilmu@rishi.is>
Cc: "guix-devel@gnu.org" <guix-devel@gnu.org>
Subject: Re: Deep vs Shallow trace: Removing the tradeoff?
Date: Sat, 17 Apr 2021 17:05:24 +0200	[thread overview]
Message-ID: <87zgxxt0i3.fsf@gnu.org> (raw)
In-Reply-To: <QHEt3fDyHGnBgsI6dv8BUBDB24fOVAfEXiEzDfg7sjVXr3DxuxY-ME4qIzikE-wkqCk-0pdgnQjdktFSCD-wRQ7yE8t__I37J0bpDn_X2og=@rishi.is> (ilmu@rishi.is's message of "Fri, 02 Apr 2021 15:45:18 +0000")

Hi,

ilmu <ilmu@rishi.is> skribis:

> To drive the point home: If the artefact has the same hash as it did before then clearly the underlying change did not affect it. Early cut-off is therefore not possible in the case where the program being depended on is supposed to be used at runtime.
>
> This is at least how I am thinking about it, I think this would be a good incremental improvement on the state of the art but it would still have these limitations.

What’s currently implemented is memoization: the hash (of the .drv and
that of the output(s)) is computed over all the inputs.

Since the output file name (the one passed to “./configure --prefix” &
co.) appears in the build result 99% of the time, the content vary at
least due to occurrences of the output file name.

Thus, content comparison are not doable as is.  What would help is
content comparison _modulo_ output file name(s).

But again, “same hash as it did before” is a framing that doesn’t hold
in a purely functional, stateless context.

Ludo’.


  reply	other threads:[~2021-04-17 15:05 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-27 16:56 Deep vs Shallow trace: Removing the tradeoff? ilmu
2021-03-28  0:50 ` Julien Lepiller
2021-03-28 23:16   ` ilmu
2021-03-30 10:46     ` Ludovic Courtès
2021-03-30 20:20     ` Bengt Richter
2021-04-02 15:45       ` ilmu
2021-04-17 15:05         ` Ludovic Courtès [this message]
2021-04-18  5:51           ` ilmu

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