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From: Junio C Hamano <gitster@pobox.com>
To: Derrick Stolee <dstolee@microsoft.com>
Cc: "git\@vger.kernel.org" <git@vger.kernel.org>,
	"peff\@peff.net" <peff@peff.net>,
	"avarab\@gmail.com" <avarab@gmail.com>,
	"sbeller\@google.com" <sbeller@google.com>,
	"larsxschneider\@gmail.com" <larsxschneider@gmail.com>,
	"bmwill\@google.com" <bmwill@google.com>
Subject: Re: [PATCH v2 07/10] commit-graph.txt: update future work
Date: Thu, 12 Apr 2018 18:12:38 +0900	[thread overview]
Message-ID: <xmqqfu403i0p.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <20180409164131.37312-8-dstolee@microsoft.com> (Derrick Stolee's message of "Mon, 9 Apr 2018 16:42:07 +0000")

Derrick Stolee <dstolee@microsoft.com> writes:

> +Here is a diagram to visualize the shape of the full commit graph, and
> +how different generation numbers relate:
> +
> +    +-----------------------------------------+
> +    | GENERATION_NUMBER_INFINITY = 0xFFFFFFFF |
> +    +-----------------------------------------+
> +	    |            |      ^
> +	    |            |      |
> +	    |            +------+
> +	    |         [gen(A) = gen(B)]
> +	    V
> +    +-------------------------------------+
> +    | 0 < commit->generation < 0x40000000 |
> +    +-------------------------------------+
> +	    |            |      ^
> +	    |            |      |
> +	    |            +------+
> +	    |        [gen(A) > gen(B)]
> +	    V
> +    +-------------------------------------+
> +    | GENERATION_NUMBER_ZERO = 0          |
> +    +-------------------------------------+
> +			 |      ^
> +			 |      |
> +			 +------+
> +		     [gen(A) = gen(B)]

It may be just me but all I can read out of the above is that
commit->generation may store 0xFFFFFFFF, a value between 0 and
0x40000000, or 0.  I cannot quite tell what the notation [gen(A)
<cmp> gen(B)] is trying to say.  I am guessing "Two generation
numbers within the 'valid' range can be compared" is what the second
one is trying to say, but it is much less interesting to know that
two infinities compare equal than how generation numbers from
different classes compare, which cannot be depicted in the above
notation, I am afraid.  For example, don't we want to say that a
commit with INF can never be reached by a commit with a valid
generation number, or something like that?

>  Design Details
>  --------------
>  
> @@ -98,17 +141,12 @@ Future Work
>  - The 'commit-graph' subcommand does not have a "verify" mode that is
>    necessary for integration with fsck.
>  
> -- The file format includes room for precomputed generation numbers. These
> -  are not currently computed, so all generation numbers will be marked as
> -  0 (or "uncomputed"). A later patch will include this calculation.
> -
>  - After computing and storing generation numbers, we must make graph
>    walks aware of generation numbers to gain the performance benefits they
>    enable. This will mostly be accomplished by swapping a commit-date-ordered
>    priority queue with one ordered by generation number. The following
> -  operations are important candidates:
> +  operation is an important candidate:

Good.

  reply	other threads:[~2018-04-12  9:12 UTC|newest]

Thread overview: 162+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-03 16:51 [PATCH 0/6] Compute and consume generation numbers Derrick Stolee
2018-04-03 16:51 ` [PATCH 1/6] object.c: parse commit in graph first Derrick Stolee
2018-04-03 18:21   ` Jonathan Tan
2018-04-03 18:28     ` Jeff King
2018-04-03 18:32       ` Derrick Stolee
2018-04-03 16:51 ` [PATCH 2/6] commit: add generation number to struct commmit Derrick Stolee
2018-04-03 18:05   ` Brandon Williams
2018-04-03 18:28     ` Jeff King
2018-04-03 18:31       ` Derrick Stolee
2018-04-03 18:32       ` Brandon Williams
2018-04-03 18:44       ` Stefan Beller
2018-04-03 23:17       ` Ramsay Jones
2018-04-03 23:19         ` Jeff King
2018-04-03 18:24   ` Jonathan Tan
2018-04-03 16:51 ` [PATCH 3/6] commit-graph: compute generation numbers Derrick Stolee
2018-04-03 18:30   ` Jonathan Tan
2018-04-03 18:49     ` Stefan Beller
2018-04-03 16:51 ` [PATCH 4/6] commit: use generations in paint_down_to_common() Derrick Stolee
2018-04-03 18:31   ` Stefan Beller
2018-04-03 18:31   ` Jonathan Tan
2018-04-03 16:51 ` [PATCH 5/6] commit.c: use generation to halt paint walk Derrick Stolee
2018-04-03 19:01   ` Jonathan Tan
2018-04-03 16:51 ` [PATCH 6/6] commit-graph.txt: update future work Derrick Stolee
2018-04-03 19:04   ` Jonathan Tan
2018-04-03 16:56 ` [PATCH 0/6] Compute and consume generation numbers Derrick Stolee
2018-04-03 18:03 ` Brandon Williams
2018-04-03 18:29   ` Derrick Stolee
2018-04-03 18:47     ` Jeff King
2018-04-03 19:05       ` Jeff King
2018-04-04 15:45         ` [PATCH 7/6] ref-filter: use generation number for --contains Derrick Stolee
2018-04-04 15:45           ` [PATCH 8/6] commit: use generation numbers for in_merge_bases() Derrick Stolee
2018-04-04 15:48             ` Derrick Stolee
2018-04-04 17:01               ` Brandon Williams
2018-04-04 18:24               ` Jeff King
2018-04-04 18:53                 ` Derrick Stolee
2018-04-04 18:59                   ` Jeff King
2018-04-04 18:22           ` [PATCH 7/6] ref-filter: use generation number for --contains Jeff King
2018-04-04 19:06             ` Derrick Stolee
2018-04-04 19:16               ` Jeff King
2018-04-04 19:22                 ` Derrick Stolee
2018-04-04 19:42                   ` Jeff King
2018-04-04 19:45                     ` Derrick Stolee
2018-04-04 19:46                       ` Jeff King
2018-04-07 17:09     ` [PATCH 0/6] Compute and consume generation numbers Jakub Narebski
2018-04-07 16:55 ` Jakub Narebski
2018-04-08  1:06   ` Derrick Stolee
2018-04-11 19:32     ` Jakub Narebski
2018-04-11 19:58       ` Derrick Stolee
2018-04-14 16:52         ` Jakub Narebski
2018-04-21 20:44           ` Jakub Narebski
2018-04-23 13:54             ` Derrick Stolee
2018-04-09 16:41 ` [PATCH v2 00/10] " Derrick Stolee
2018-04-09 16:41   ` [PATCH v2 01/10] object.c: parse commit in graph first Derrick Stolee
2018-04-09 16:41   ` [PATCH v2 02/10] merge: check config before loading commits Derrick Stolee
2018-04-11  2:12     ` Junio C Hamano
2018-04-11 12:49       ` Derrick Stolee
2018-04-09 16:42   ` [PATCH v2 03/10] commit: add generation number to struct commmit Derrick Stolee
2018-04-09 17:59     ` Stefan Beller
2018-04-11  2:31     ` Junio C Hamano
2018-04-11 12:57       ` Derrick Stolee
2018-04-11 23:28         ` Junio C Hamano
2018-04-09 16:42   ` [PATCH v2 04/10] commit-graph: compute generation numbers Derrick Stolee
2018-04-11  2:51     ` Junio C Hamano
2018-04-11 13:02       ` Derrick Stolee
2018-04-11 18:49         ` Stefan Beller
2018-04-11 19:26         ` Eric Sunshine
2018-04-09 16:42   ` [PATCH v2 05/10] commit: use generations in paint_down_to_common() Derrick Stolee
2018-04-09 16:42   ` [PATCH v2 06/10] commit.c: use generation to halt paint walk Derrick Stolee
2018-04-11  3:02     ` Junio C Hamano
2018-04-11 13:24       ` Derrick Stolee
2018-04-09 16:42   ` [PATCH v2 07/10] commit-graph.txt: update future work Derrick Stolee
2018-04-12  9:12     ` Junio C Hamano [this message]
2018-04-12 11:35       ` Derrick Stolee
2018-04-13  9:53         ` Jakub Narebski
2018-04-09 16:42   ` [PATCH v2 08/10] ref-filter: use generation number for --contains Derrick Stolee
2018-04-09 16:42   ` [PATCH v2 09/10] commit: use generation numbers for in_merge_bases() Derrick Stolee
2018-04-09 16:42   ` [PATCH v2 10/10] commit: add short-circuit to paint_down_to_common() Derrick Stolee
2018-04-17 17:00   ` [PATCH v3 0/9] Compute and consume generation numbers Derrick Stolee
2018-04-17 17:00     ` [PATCH v3 1/9] commit: add generation number to struct commmit Derrick Stolee
2018-04-17 17:00     ` [PATCH v3 2/9] commit-graph: compute generation numbers Derrick Stolee
2018-04-17 17:00     ` [PATCH v3 3/9] commit: use generations in paint_down_to_common() Derrick Stolee
2018-04-18 14:31       ` Jakub Narebski
2018-04-18 14:46         ` Derrick Stolee
2018-04-17 17:00     ` [PATCH v3 4/9] commit-graph.txt: update design document Derrick Stolee
2018-04-18 19:47       ` Jakub Narebski
2018-04-17 17:00     ` [PATCH v3 5/9] ref-filter: use generation number for --contains Derrick Stolee
2018-04-18 21:02       ` Jakub Narebski
2018-04-23 14:22         ` Derrick Stolee
2018-04-24 18:56           ` Jakub Narebski
2018-04-25 14:11             ` Derrick Stolee
2018-04-17 17:00     ` [PATCH v3 6/9] commit: use generation numbers for in_merge_bases() Derrick Stolee
2018-04-18 22:15       ` Jakub Narebski
2018-04-23 14:31         ` Derrick Stolee
2018-04-17 17:00     ` [PATCH v3 7/9] commit: add short-circuit to paint_down_to_common() Derrick Stolee
2018-04-18 23:19       ` Jakub Narebski
2018-04-23 14:40         ` Derrick Stolee
2018-04-23 21:38           ` Jakub Narebski
2018-04-24 12:31             ` Derrick Stolee
2018-04-19  8:32       ` Jakub Narebski
2018-04-17 17:00     ` [PATCH v3 8/9] commit-graph: always load commit-graph information Derrick Stolee
2018-04-17 17:50       ` Derrick Stolee
2018-04-19  0:02       ` Jakub Narebski
2018-04-23 14:49         ` Derrick Stolee
2018-04-17 17:00     ` [PATCH v3 9/9] merge: check config before loading commits Derrick Stolee
2018-04-19  0:04     ` [PATCH v3 0/9] Compute and consume generation numbers Jakub Narebski
2018-04-23 14:54       ` Derrick Stolee
2018-04-25 14:37     ` [PATCH v4 00/10] " Derrick Stolee
2018-04-25 14:37       ` [PATCH v4 01/10] ref-filter: fix outdated comment on in_commit_list Derrick Stolee
2018-04-28 17:54         ` Jakub Narebski
2018-04-25 14:37       ` [PATCH v4 02/10] commit: add generation number to struct commmit Derrick Stolee
2018-04-28 22:35         ` Jakub Narebski
2018-04-30 12:05           ` Derrick Stolee
2018-04-25 14:37       ` [PATCH v4 03/10] commit-graph: compute generation numbers Derrick Stolee
2018-04-26  2:35         ` Junio C Hamano
2018-04-26 12:58           ` Derrick Stolee
2018-04-26 13:49             ` Derrick Stolee
2018-04-29  9:08         ` Jakub Narebski
2018-05-01 12:10           ` Derrick Stolee
2018-05-02 16:15             ` Jakub Narebski
2018-04-25 14:37       ` [PATCH v4 04/10] commit: use generations in paint_down_to_common() Derrick Stolee
2018-04-26  3:22         ` Junio C Hamano
2018-04-26  9:02           ` Jakub Narebski
2018-04-28 14:38             ` Jakub Narebski
2018-04-29 15:40         ` Jakub Narebski
2018-04-25 14:37       ` [PATCH v4 06/10] ref-filter: use generation number for --contains Derrick Stolee
2018-04-30 16:34         ` Jakub Narebski
2018-04-25 14:37       ` [PATCH v4 05/10] commit-graph: always load commit-graph information Derrick Stolee
2018-04-29 22:14         ` Jakub Narebski
2018-05-01 12:19           ` Derrick Stolee
2018-04-29 22:18         ` Jakub Narebski
2018-04-25 14:37       ` [PATCH v4 07/10] commit: use generation numbers for in_merge_bases() Derrick Stolee
2018-04-30 17:05         ` Jakub Narebski
2018-04-25 14:38       ` [PATCH v4 08/10] commit: add short-circuit to paint_down_to_common() Derrick Stolee
2018-04-30 22:19         ` Jakub Narebski
2018-05-01 11:47           ` Derrick Stolee
2018-05-02 13:05             ` Jakub Narebski
2018-05-02 13:42               ` Derrick Stolee
2018-04-25 14:38       ` [PATCH v4 09/10] merge: check config before loading commits Derrick Stolee
2018-04-30 22:54         ` Jakub Narebski
2018-05-01 11:52           ` Derrick Stolee
2018-05-02 11:41             ` Jakub Narebski
2018-04-25 14:38       ` [PATCH v4 10/10] commit-graph.txt: update design document Derrick Stolee
2018-04-30 23:32         ` Jakub Narebski
2018-05-01 12:00           ` Derrick Stolee
2018-05-02  7:57             ` Jakub Narebski
2018-04-25 14:40       ` [PATCH v4 00/10] Compute and consume generation numbers Derrick Stolee
2018-04-28 17:28         ` Jakub Narebski
2018-05-01 12:47       ` [PATCH v5 00/11] " Derrick Stolee
2018-05-01 12:47         ` [PATCH v5 01/11] ref-filter: fix outdated comment on in_commit_list Derrick Stolee
2018-05-01 12:47         ` [PATCH v5 02/11] commit: add generation number to struct commmit Derrick Stolee
2018-05-01 12:47         ` [PATCH v5 03/11] commit-graph: compute generation numbers Derrick Stolee
2018-05-01 12:47         ` [PATCH v5 04/11] commit: use generations in paint_down_to_common() Derrick Stolee
2018-05-01 12:47         ` [PATCH v5 05/11] commit-graph: always load commit-graph information Derrick Stolee
2018-05-01 12:47         ` [PATCH v5 06/11] ref-filter: use generation number for --contains Derrick Stolee
2018-05-01 12:47         ` [PATCH v5 07/11] commit: use generation numbers for in_merge_bases() Derrick Stolee
2018-05-01 12:47         ` [PATCH v5 08/11] commit: add short-circuit to paint_down_to_common() Derrick Stolee
2018-05-01 12:47         ` [PATCH v5 09/11] commit: use generation number in remove_redundant() Derrick Stolee
2018-05-01 15:37           ` Derrick Stolee
2018-05-03 18:45           ` Jakub Narebski
2018-05-01 12:47         ` [PATCH v5 10/11] merge: check config before loading commits Derrick Stolee
2018-05-01 12:47         ` [PATCH v5 11/11] commit-graph.txt: update design document Derrick Stolee
2018-05-03 11:18         ` [PATCH v5 00/11] Compute and consume generation numbers Jakub Narebski

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