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From: jnareb@gmail.com (Jakub Narębski)
To: "Abhishek Kumar via GitGitGadget" <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, "Derrick Stolee" <stolee@gmail.com>,
	"Taylor Blau" <me@ttaylorr.com>,
	"Abhishek Kumar" <abhishekkumar8222@gmail.com>,
	"Jakub Narębski" <jnareb@gmail.com>
Subject: Re: [PATCH v3 04/11] commit-graph: consolidate compare_commits_by_gen
Date: Fri, 21 Aug 2020 13:05:19 +0200
Message-ID: <85sgcgmf80.fsf@gmail.com> (raw)
In-Reply-To: <6a0cde983d9ed20f043a4977313d714154602012.1597509583.git.gitgitgadget@gmail.com> (Abhishek Kumar via GitGitGadget's message of "Sat, 15 Aug 2020 16:39:36 +0000")

"Abhishek Kumar via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Abhishek Kumar <abhishekkumar8222@gmail.com>
>
> Comparing commits by generation has been independently defined twice, in
> commit-reach and commit. Let's simplify the implementation by moving
> compare_commits_by_gen() to commit-graph.

All right, seems reasonable.

Though it might be not obvious that the second repetition of code
comparing commits by generation is part of commit.c's
compare_commits_by_gen_then_commit_date().

Is't it micro-pessimization though, or can the compiler inline function
across different files?  On the other hand it reduces code duplication...

>
> Signed-off-by: Abhishek Kumar <abhishekkumar8222@gmail.com>
> Reviewed-by: Taylor Blau <me@ttaylorr.com>
> Signed-off-by: Abhishek Kumar <abhishekkumar8222@gmail.com>
> ---
>  commit-graph.c | 15 +++++++++++++++
>  commit-graph.h |  2 ++
>  commit-reach.c | 15 ---------------
>  commit.c       |  9 +++------
>  4 files changed, 20 insertions(+), 21 deletions(-)
>
> diff --git a/commit-graph.c b/commit-graph.c
> index af8d9cc45e..fb6e2bf18f 100644
> --- a/commit-graph.c
> +++ b/commit-graph.c
> @@ -112,6 +112,21 @@ uint32_t commit_graph_generation(const struct commit *c)
>  	return data->generation;
>  }
>
> +int compare_commits_by_gen(const void *_a, const void *_b)
> +{
> +	const struct commit *a = _a, *b = _b;
> +	const uint32_t generation_a = commit_graph_generation(a);
> +	const uint32_t generation_b = commit_graph_generation(b);

All right, this function used protected access to generation number of a
commit, that is it correctly handles the case where commit '_a' and/or
'_b' are new enough to be not present in the commit graph.

That is why we cannot simply use commit_gen_cmp(), that is the function
used for sorting during `git commit-graph write --reachable --changed-paths`,
because after 1st patch it access the slab directly.

> +
> +	/* older commits first */

Nice!  Thanks for adding this comment.

Though it might be good idea to add this comment also to the header
file, commit-graph.h, because the fact that compare_commits_by_gen()
and compare_commits_by_gen_then_commit_date() sort in different
order is not something that we can see from their names.  Well,
they have slightly different sigatures...

> +	if (generation_a < generation_b)
> +		return -1;
> +	else if (generation_a > generation_b)
> +		return 1;
> +
> +	return 0;
> +}
> +
>  static struct commit_graph_data *commit_graph_data_at(const struct commit *c)
>  {
>  	unsigned int i, nth_slab;
> diff --git a/commit-graph.h b/commit-graph.h
> index 09a97030dc..701e3d41aa 100644
> --- a/commit-graph.h
> +++ b/commit-graph.h
> @@ -146,4 +146,6 @@ struct commit_graph_data {
>   */
>  uint32_t commit_graph_generation(const struct commit *);
>  uint32_t commit_graph_position(const struct commit *);
> +
> +int compare_commits_by_gen(const void *_a, const void *_b);

All right.

>  #endif
> diff --git a/commit-reach.c b/commit-reach.c
> index efd5925cbb..c83cc291e7 100644
> --- a/commit-reach.c
> +++ b/commit-reach.c
> @@ -561,21 +561,6 @@ int commit_contains(struct ref_filter *filter, struct commit *commit,
>  	return repo_is_descendant_of(the_repository, commit, list);
>  }
>
> -static int compare_commits_by_gen(const void *_a, const void *_b)
> -{
> -	const struct commit *a = *(const struct commit * const *)_a;
> -	const struct commit *b = *(const struct commit * const *)_b;
> -
> -	uint32_t generation_a = commit_graph_generation(a);
> -	uint32_t generation_b = commit_graph_generation(b);
> -
> -	if (generation_a < generation_b)
> -		return -1;
> -	if (generation_a > generation_b)
> -		return 1;
> -	return 0;
> -}

All right, commit-reach.c includes commit-graph.h, so now it simply uses
compare_commits_by_gen() that was copied to commit-graph.c.

> -
>  int can_all_from_reach_with_flag(struct object_array *from,
>  				 unsigned int with_flag,
>  				 unsigned int assign_flag,
> diff --git a/commit.c b/commit.c
> index 4ce8cb38d5..bd6d5e587f 100644
> --- a/commit.c
> +++ b/commit.c
> @@ -731,14 +731,11 @@ int compare_commits_by_author_date(const void *a_, const void *b_,
>  int compare_commits_by_gen_then_commit_date(const void *a_, const void *b_, void *unused)
>  {
>  	const struct commit *a = a_, *b = b_;
> -	const uint32_t generation_a = commit_graph_generation(a),
> -		       generation_b = commit_graph_generation(b);
> +	int ret_val = compare_commits_by_gen(a_, b_);
>
>  	/* newer commits first */

Maybe this comment should be put in the header file, near this functionn
declaration?

> -	if (generation_a < generation_b)
> -		return 1;
> -	else if (generation_a > generation_b)
> -		return -1;
> +	if (ret_val)
> +		return -ret_val;

All right, this handles reversed sorting order of compare_commits_by_gen().

>
>  	/* use date as a heuristic when generations are equal */
>  	if (a->date < b->date)

Best,
-- 
Jakub Narębski

  parent reply index

Thread overview: 129+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-28  9:13 [PATCH 0/6] [GSoC] Implement Corrected Commit Date Abhishek Kumar via GitGitGadget
2020-07-28  9:13 ` [PATCH 1/6] commit-graph: fix regression when computing bloom filter Abhishek Kumar via GitGitGadget
2020-07-28 15:28   ` Taylor Blau
2020-07-30  5:24     ` Abhishek Kumar
2020-08-04  0:46   ` Jakub Narębski
2020-08-04  0:56     ` Taylor Blau
2020-08-04 10:10       ` Jakub Narębski
2020-08-04  7:55     ` Jakub Narębski
2020-07-28  9:13 ` [PATCH 2/6] revision: parse parent in indegree_walk_step() Abhishek Kumar via GitGitGadget
2020-07-28 13:00   ` Derrick Stolee
2020-07-28 15:30     ` Taylor Blau
2020-08-05 23:16   ` Jakub Narębski
2020-07-28  9:13 ` [PATCH 3/6] commit-graph: consolidate fill_commit_graph_info Abhishek Kumar via GitGitGadget
2020-07-28 13:14   ` Derrick Stolee
2020-07-28 15:19     ` René Scharfe
2020-07-28 15:58       ` Derrick Stolee
2020-07-28 16:01     ` Taylor Blau
2020-07-30  6:07     ` Abhishek Kumar
2020-07-28  9:13 ` [PATCH 4/6] commit-graph: consolidate compare_commits_by_gen Abhishek Kumar via GitGitGadget
2020-07-28 16:03   ` Taylor Blau
2020-07-28  9:13 ` [PATCH 5/6] commit-graph: implement generation data chunk Abhishek Kumar via GitGitGadget
2020-07-28 16:12   ` Taylor Blau
2020-07-30  6:52     ` Abhishek Kumar
2020-07-28  9:13 ` [PATCH 6/6] commit-graph: implement corrected commit date offset Abhishek Kumar via GitGitGadget
2020-07-28 15:55   ` Derrick Stolee
2020-07-28 16:23     ` Taylor Blau
2020-07-30  7:27     ` Abhishek Kumar
2020-07-28 14:54 ` [PATCH 0/6] [GSoC] Implement Corrected Commit Date Taylor Blau
2020-07-30  7:47   ` Abhishek Kumar
2020-07-28 16:35 ` Derrick Stolee
2020-08-09  2:53 ` [PATCH v2 00/10] " Abhishek Kumar via GitGitGadget
2020-08-09  2:53   ` [PATCH v2 01/10] commit-graph: fix regression when computing bloom filter Abhishek Kumar via GitGitGadget
2020-08-09  2:53   ` [PATCH v2 02/10] revision: parse parent in indegree_walk_step() Abhishek Kumar via GitGitGadget
2020-08-09  2:53   ` [PATCH v2 03/10] commit-graph: consolidate fill_commit_graph_info Abhishek Kumar via GitGitGadget
2020-08-09  2:53   ` [PATCH v2 04/10] commit-graph: consolidate compare_commits_by_gen Abhishek Kumar via GitGitGadget
2020-08-09  2:53   ` [PATCH v2 05/10] commit-graph: implement generation data chunk Abhishek Kumar via GitGitGadget
2020-08-10 16:28     ` Derrick Stolee
2020-08-11 11:03       ` Abhishek Kumar
2020-08-11 12:27         ` Derrick Stolee
2020-08-11 18:58           ` Taylor Blau
2020-08-09  2:53   ` [PATCH v2 06/10] commit-graph: return 64-bit generation number Abhishek Kumar via GitGitGadget
2020-08-09  2:53   ` [PATCH v2 07/10] commit-graph: implement corrected commit date Abhishek Kumar via GitGitGadget
2020-08-10 14:23     ` Derrick Stolee
2020-08-14  4:59       ` Abhishek Kumar
2020-08-14 12:24         ` Derrick Stolee
2020-08-09  2:53   ` [PATCH v2 08/10] commit-graph: handle mixed generation commit chains Abhishek Kumar via GitGitGadget
2020-08-10 16:42     ` Derrick Stolee
2020-08-11 11:36       ` Abhishek Kumar
2020-08-11 12:43         ` Derrick Stolee
2020-08-09  2:53   ` [PATCH v2 09/10] commit-reach: use corrected commit dates in paint_down_to_common() Abhishek Kumar via GitGitGadget
2020-08-09  2:53   ` [PATCH v2 10/10] doc: add corrected commit date info Abhishek Kumar via GitGitGadget
2020-08-10 16:47   ` [PATCH v2 00/10] [GSoC] Implement Corrected Commit Date Derrick Stolee
2020-08-15 16:39   ` [PATCH v3 00/11] " Abhishek Kumar via GitGitGadget
2020-08-15 16:39     ` [PATCH v3 01/11] commit-graph: fix regression when computing bloom filter Abhishek Kumar via GitGitGadget
2020-08-17 22:30       ` Jakub Narębski
2020-08-15 16:39     ` [PATCH v3 02/11] revision: parse parent in indegree_walk_step() Abhishek Kumar via GitGitGadget
2020-08-18 14:18       ` Jakub Narębski
2020-08-15 16:39     ` [PATCH v3 03/11] commit-graph: consolidate fill_commit_graph_info Abhishek Kumar via GitGitGadget
2020-08-19 17:54       ` Jakub Narębski
2020-08-21  4:11         ` Abhishek Kumar
2020-08-25 11:11           ` Jakub Narębski
2020-09-01 11:35             ` Abhishek Kumar
2020-08-15 16:39     ` [PATCH v3 04/11] commit-graph: consolidate compare_commits_by_gen Abhishek Kumar via GitGitGadget
2020-08-17 13:22       ` Derrick Stolee
2020-08-21 11:05       ` Jakub Narębski [this message]
2020-08-15 16:39     ` [PATCH v3 05/11] commit-graph: return 64-bit generation number Abhishek Kumar via GitGitGadget
2020-08-21 13:14       ` Jakub Narębski
2020-08-25  5:04         ` Abhishek Kumar
2020-08-25 12:18           ` Jakub Narębski
2020-09-01 12:06             ` Abhishek Kumar
2020-09-03 13:42               ` Jakub Narębski
2020-09-05 17:21                 ` Abhishek Kumar
2020-09-13 15:39                   ` Jakub Narębski
2020-09-28 21:48                     ` Jakub Narębski
2020-10-05  5:25                       ` Abhishek Kumar
2020-08-15 16:39     ` [PATCH v3 06/11] commit-graph: add a slab to store topological levels Abhishek Kumar via GitGitGadget
2020-08-21 18:43       ` Jakub Narębski
2020-08-25  6:14         ` Abhishek Kumar
2020-08-25  7:33           ` Jakub Narębski
2020-08-25  7:56             ` Jakub Narębski
2020-09-01 10:26               ` Abhishek Kumar
2020-09-03  9:25                 ` Jakub Narębski
2020-08-15 16:39     ` [PATCH v3 07/11] commit-graph: implement corrected commit date Abhishek Kumar via GitGitGadget
2020-08-22  0:05       ` Jakub Narębski
2020-08-25  6:49         ` Abhishek Kumar
2020-08-25 10:07           ` Jakub Narębski
2020-09-01 11:01             ` Abhishek Kumar
2020-08-15 16:39     ` [PATCH v3 08/11] commit-graph: implement generation data chunk Abhishek Kumar via GitGitGadget
2020-08-22 13:09       ` Jakub Narębski
2020-08-15 16:39     ` [PATCH v3 09/11] commit-graph: use generation v2 only if entire chain does Abhishek Kumar via GitGitGadget
2020-08-22 17:14       ` Jakub Narębski
2020-08-26  7:15         ` Abhishek Kumar
2020-08-26 10:38           ` Jakub Narębski
2020-08-15 16:39     ` [PATCH v3 10/11] commit-reach: use corrected commit dates in paint_down_to_common() Abhishek Kumar via GitGitGadget
2020-08-22 19:09       ` Jakub Narębski
2020-09-01 10:08         ` Abhishek Kumar
2020-09-03 19:11           ` Jakub Narębski
2020-08-15 16:39     ` [PATCH v3 11/11] doc: add corrected commit date info Abhishek Kumar via GitGitGadget
2020-08-22 22:20       ` Jakub Narębski
2020-08-27  6:39         ` Abhishek Kumar
2020-08-27 12:43           ` Jakub Narębski
2020-08-27 13:15           ` Derrick Stolee
2020-09-01 13:01             ` Abhishek Kumar
2020-08-17  0:13     ` [PATCH v3 00/11] [GSoC] Implement Corrected Commit Date Jakub Narębski
     [not found]       ` <CANQwDwdKp7oKy9BeKdvKhwPUiq0R5MS8TCw-eWGCYCoMGv=G-g@mail.gmail.com>
2020-08-17  1:32         ` Fwd: " Taylor Blau
2020-08-17  7:56           ` Jakub Narębski
2020-08-18  6:12       ` Abhishek Kumar
2020-08-23 15:27       ` Jakub Narębski
2020-08-24  2:49         ` Abhishek Kumar
2020-10-07 14:09     ` [PATCH v4 00/10] " Abhishek Kumar via GitGitGadget
2020-10-07 14:09       ` [PATCH v4 01/10] commit-graph: fix regression when computing Bloom filters Abhishek Kumar via GitGitGadget
2020-10-24 23:16         ` Jakub Narębski
2020-10-25 20:58           ` Taylor Blau
2020-10-07 14:09       ` [PATCH v4 02/10] revision: parse parent in indegree_walk_step() Abhishek Kumar via GitGitGadget
2020-10-24 23:41         ` Jakub Narębski
2020-10-07 14:09       ` [PATCH v4 03/10] commit-graph: consolidate fill_commit_graph_info Abhishek Kumar via GitGitGadget
2020-10-25 10:52         ` Jakub Narębski
2020-10-27  6:33           ` Abhishek Kumar
2020-10-07 14:09       ` [PATCH v4 04/10] commit-graph: return 64-bit generation number Abhishek Kumar via GitGitGadget
2020-10-25 13:48         ` Jakub Narębski
2020-10-07 14:09       ` [PATCH v4 05/10] commit-graph: add a slab to store topological levels Abhishek Kumar via GitGitGadget
2020-10-25 22:17         ` Jakub Narębski
2020-10-07 14:09       ` [PATCH v4 06/10] commit-graph: implement corrected commit date Abhishek Kumar via GitGitGadget
2020-10-27 18:53         ` Jakub Narębski
2020-10-07 14:09       ` [PATCH v4 07/10] commit-graph: implement generation data chunk Abhishek Kumar via GitGitGadget
2020-10-30 12:45         ` Jakub Narębski
2020-10-07 14:09       ` [PATCH v4 08/10] commit-graph: use generation v2 only if entire chain does Abhishek Kumar via GitGitGadget
2020-10-07 14:09       ` [PATCH v4 09/10] commit-reach: use corrected commit dates in paint_down_to_common() Abhishek Kumar via GitGitGadget
2020-10-07 14:09       ` [PATCH v4 10/10] doc: add corrected commit date info Abhishek Kumar via GitGitGadget

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