From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: [PATCH] Optimize package-transitive-supported-systems
Date: Mon, 22 Dec 2014 00:37:54 +0100
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In-Reply-To: <873888n0g4.fsf@netris.org> (Mark H. Weaver's message of "Sun, 21
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To: Mark H Weaver <mhw@netris.org>
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Mark H Weaver <mhw@netris.org> skribis:

> When hydra evaluates a jobset, 'package-transitive-supported-systems' is
> called for every package+system combination.  Each of these calls
> traverses the tree of inputs, but without eliminating duplicate
> transitive-inputs.  In other words, the amount of time spent is
> proportional not to the number of transitive-inputs, but the number of
> _paths_ to all transitive-inputs.

Oops!  Though it=E2=80=99s not clear to me that it explains the problems we=
=E2=80=99re
seeing on Hydra currently, because running
build-aux/hydra/gnu-system.scm on my laptop takes ~1mn.

> This patch memoizes 'package-transitive-supported-systems', so that the
> total time to apply it to all packages is O(N).

Much better.

> From 90541f6c7e2a9e2f8a7b412532b4b5a56a10e481 Mon Sep 17 00:00:00 2001
> From: Mark H Weaver <mhw@netris.org>
> Date: Sun, 21 Dec 2014 16:21:02 -0500
> Subject: [PATCH] Optimize package-transitive-supported-systems.
>
> * guix/packages.scm (first-value): Remove.
>   (define-memoized/v): New macro.
>   (package-transitive-supported-systems): Rewrite.

LGTM, thank you!

Ludo=E2=80=99.