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From: Jakub Narebski <jnareb@gmail.com>
To: Derrick Stolee <stolee@gmail.com>
Cc: "Mike Hommey" <mh@glandium.org>,
	"SZEDER Gábor" <szeder.dev@gmail.com>,
	git@vger.kernel.org
Subject: Re: Revision walking, commit dates, slop
Date: Tue, 25 Jun 2019 09:51:48 +0200	[thread overview]
Message-ID: <86mui63xwr.fsf@gmail.com> (raw)
In-Reply-To: <86ftp9p7i8.fsf@gmail.com> (Jakub Narebski's message of "Mon, 20 May 2019 15:42:23 +0200")

Jakub Narebski <jnareb@gmail.com> writes:
> Derrick Stolee <stolee@gmail.com> writes:
>> On 5/20/2019 7:02 AM, Jakub Narebski wrote:
>>>
>>> Are there any blockers that prevent the switch to this
>>> "generation number v2"?
>>> 
>>> - Is it a problem with insufficient data to choose the correct numbering
>>>   as "generation number v2' (there can be only one)?
>>> - Is it a problem with selected "generation number v2" being
>>>   incompatibile with gen v2, and Git failing when new version of
>>>   commit-graph is used instead of softly just not using commit-graph?
>>> - Or is it something else?
[...]

>>                      Using the generation number column for the corrected
>> commit-date offsets (assuming we also guarantee the offset is strictly
>> increasing from parent to child), these new values will be backwards-
>> compatible _except_ for 'git commit-graph verify'.
>
> O.K., so the "generation number v2 (legacy)" would be incremental and
> backward-compatibile in use (though not in generation and validation).
>
> Do I understand it correctly how it is calculated:
>
>   corrected_date(C) = max(committer_date(C),
>                           max_{P ∈ parents(C)}(corrected_date(P)) + 1)
>   offset(C) = corrected_date(C) - committer_date(C)
>   gen_v2(C) = max(offset(C), max_{P ∈ parents(C)}(gen_v2(P)) + 1) 

Do you remember who first came up with this idea for backward
compatibile corrected commit date offsets (monotonically offset
corrected date)?

> Do you have benchmark for this "monotonically offset corrected commit
> date" generation number in https://github.com/derrickstolee/git/commits/reach-perf
> and https://github.com/derrickstolee/gen-test ?

I guess this will have to wait...

Best,
--
Jakub Narębski

  parent reply	other threads:[~2019-06-25  7:51 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-18  0:54 Revision walking, commit dates, slop Mike Hommey
2019-05-18  1:50 ` SZEDER Gábor
2019-05-18  3:58   ` Mike Hommey
2019-05-18  4:17     ` Mike Hommey
2019-05-18 12:01       ` SZEDER Gábor
2019-05-19 22:28         ` Jakub Narebski
2019-05-20  1:33       ` Derrick Stolee
2019-05-20 11:02         ` Jakub Narebski
2019-05-20 11:20           ` Derrick Stolee
2019-05-20 13:42             ` Jakub Narebski
2019-05-20 23:27               ` Jakub Narebski
2019-05-21  1:20                 ` Derrick Stolee
2019-05-22 18:29                   ` Jakub Narebski
2019-05-22 19:06                     ` Derrick Stolee
2019-05-23 21:04                       ` Jakub Narebski
2019-06-25  7:51               ` Jakub Narebski [this message]
2019-06-25 10:54                 ` Derrick Stolee
2019-09-18  8:43                   ` [RFC/PATCH] commit-graph: generation v5 (backward compatible date ceiling) Jakub Narebski
2019-09-18 12:26                     ` Derrick Stolee
2019-05-21 13:14         ` [PATCH] revision: use generation for A..B --topo-order queries Derrick Stolee
2019-05-21 13:59           ` [PATCH 2/2] revision: keep topo-walk free of unintersting commits Derrick Stolee
2019-05-22  2:19             ` Mike Hommey
2019-05-21  2:00   ` Revision walking, commit dates, slop Jonathan Nieder

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