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From: Derrick Stolee <stolee@gmail.com>
To: "René Scharfe" <l.s.r@web.de>, "Git Mailing List" <git@vger.kernel.org>
Cc: "SZEDER Gábor" <szeder.dev@gmail.com>,
	"Martin Ågren" <martin.agren@gmail.com>,
	"Junio C Hamano" <gitster@pobox.com>
Subject: Re: [PATCH 09/10] name-rev: generate name strings only if they are better
Date: Wed, 5 Feb 2020 10:11:44 -0500	[thread overview]
Message-ID: <3a59d8b4-3c3d-3812-9b7e-ac7e331ccd1c@gmail.com> (raw)
In-Reply-To: <77d1d053-8680-5cbe-9182-b6aec9e9b446@web.de>

On 2/4/2020 4:25 PM, René Scharfe wrote:
> -			if (create_or_update_name(parent, new_name, taggerdate,
> -						  generation, distance,
> -						  from_tag)) {
> +			parent_name = create_or_update_name(parent, taggerdate,
> +							    generation,
> +							    distance, from_tag);
> +			if (parent_name) {

As someone unfamiliar with the name-rev code, it took me a while to see why
the algorithm isn't exponential in complexity. It technically _is_, but it
is of the form 2^{N / MERGE_TRAVERSAL_WEIGHT} = 2^{N / 65535} and only if
we create a particularly nasty commit history that would never appear in the wild.

But, the critical section is the block above. The confusing part was that
create_or_update_name() returns NULL if the name is updated, but non-NULL if
a better name is created. That makes it clear that this change is saving
allocations.

Thanks,
-Stolee

  reply	other threads:[~2020-02-05 15:11 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-04 21:12 [PATCH 00/10] name-rev: improve memory usage René Scharfe
2020-02-04 21:14 ` [PATCH 01/10] name-rev: rewrite create_or_update_name() René Scharfe
2020-02-05  2:00   ` Derrick Stolee
2020-02-05  2:35     ` Taylor Blau
2020-02-05 16:45   ` Andrei Rybak
2020-02-05 16:47     ` René Scharfe
2020-02-04 21:15 ` [PATCH 02/10] name-rev: remove unused typedef René Scharfe
2020-02-04 21:16 ` [PATCH 03/10] name-rev: respect const qualifier René Scharfe
2020-02-04 21:17 ` [PATCH 04/10] name-rev: don't leak path copy in name_ref() René Scharfe
2020-02-05 14:35   ` Derrick Stolee
2020-02-04 21:20 ` [PATCH 05/10] name-rev: don't _peek() in create_or_update_name() René Scharfe
2020-02-04 21:22 ` [PATCH 06/10] name-rev: put struct rev_name into commit slab René Scharfe
2020-02-04 21:23 ` [PATCH 07/10] name-rev: factor out get_parent_name() René Scharfe
2020-02-04 21:24 ` [PATCH 08/10] name-rev: pre-size buffer in get_parent_name() René Scharfe
2020-02-05  3:19   ` Derrick Stolee
2020-02-05 15:16     ` René Scharfe
2020-02-04 21:25 ` [PATCH 09/10] name-rev: generate name strings only if they are better René Scharfe
2020-02-05 15:11   ` Derrick Stolee [this message]
2020-02-05 15:50     ` René Scharfe
2020-02-04 21:26 ` [PATCH 10/10] name-rev: release unused name strings René Scharfe
2020-02-05 15:19   ` Derrick Stolee
2020-02-05  3:28 ` [PATCH 00/10] name-rev: improve memory usage Derrick Stolee
2020-02-05 15:20   ` Derrick Stolee
2020-02-05 17:19 ` [PATCH 01/10 RESEND AUTHOR FIXED] name-rev: rewrite create_or_update_name() René Scharfe
2020-02-05 17:50 ` [PATCH 11/10] name-rev: sort tip names before applying René Scharfe
2020-02-05 18:23   ` Junio C Hamano
2020-02-05 18:55     ` René Scharfe

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