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From: Derrick Stolee <stolee@gmail.com>
To: "René Scharfe" <l.s.r@web.de>,
	"Junio C Hamano" <gitster@pobox.com>,
	"Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, Michael Haggerty <mhagger@alum.mit.edu>,
	me@ttaylorr.com, peff@peff.net,
	Derrick Stolee <derrickstolee@github.com>,
	Derrick Stolee <dstolee@microsoft.com>
Subject: Re: [PATCH 1/3] commit-reach: use one walk in remove_redundant()
Date: Sat, 30 Jan 2021 22:52:59 -0500	[thread overview]
Message-ID: <75225d59-877e-92ad-1370-632d40af71cf@gmail.com> (raw)
In-Reply-To: <198f7766-190d-d361-d6f4-23adefedaf6c@web.de>

On 1/29/2021 12:11 PM, René Scharfe wrote:
> Am 28.01.21 um 21:51 schrieb Junio C Hamano:
>> "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:
>>> +	/* rearrange array */
>>> +	dup = xcalloc(cnt, sizeof(struct commit *));
>>> +	COPY_ARRAY(dup, array, cnt);
>>> +	for (i = 0; i < cnt; i++) {
>>> +		if (dup[i]->object.flags & STALE) {
>>> +			int insert = cnt - 1 - (i - count_non_stale);
>>> +			array[insert] = dup[i];
>>> +		} else {
>>> +			array[count_non_stale] = dup[i];
>>> +			count_non_stale++;
>>> +		}
>>> +	}
>>> +	free(dup);
>>
>> The "fill stale ones from the end, non-stale ones from the
>> beginning" in the loop looks unnecessarily complex to me.  I wonder
>> if we can do only the "fill non-stale ones from the beginning" half,
>> i.e.
>>
>> 	for (i = count_non_stale = 0; i < cnt; i++) {
>> 		if (dup[i] is not stale)
>> 			array[count_non_stale++] = dup[i];
>> 	}
>>
>> without the "keep the stale one at the end of array[]", and clear
>> marks using what is in dup[] as starting points before discarding
>> dup[]?
>>
>> Or do the callers still look at the entries beyond count_non_stale?
> 
> Had the same reaction.  Both callers ignore the stale entries.

Ok, I can update that logic accordingly. I wanted to keep consistent
with the comment at the start of the method:

	/*
	 * Some commit in the array may be an ancestor of
	 * another commit.  Move such commit to the end of
	 * the array, and return the number of commits that
	 * are independent from each other.
	 */

but if no caller actually needs that, then I can remove this
behavior. Anyone mind if it is a follow-up patch to change this
part of the behavior?

>> Other than that, nicely done.
>>
>>> +	/* clear marks */
>>> +	for (i = 0; i < cnt; i++) {
>>> +		struct commit_list *parents;
>>> +		parents = array[i]->parents;
>>> +
>>> +		while (parents) {
>>> +			clear_commit_marks(parents->item, STALE);
>>> +			parents = parents->next;
>>>  		}
> 
> This loop clears STALE from the parents of both the non-stale and
> stale entries.  OK.  Should it also clear it from the stale entries
> themselves?

clear_commit_marks() walks commits starting from the input commit
(parents->item in this case) and clears the STALE bit as long as
it is present. This way, the accumulated clear_commit_marks() will
walk each commit only once _and_ will visit any of the commits from
'array' that received the STALE bit during the above walk.

Thanks,
-Stolee

  reply	other threads:[~2021-01-31  3:53 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-28 16:24 [PATCH 0/3] Speed up remove_redundant() Derrick Stolee via GitGitGadget
2021-01-28 16:24 ` [PATCH 1/3] commit-reach: use one walk in remove_redundant() Derrick Stolee via GitGitGadget
2021-01-28 20:51   ` Junio C Hamano
2021-01-29 17:11     ` René Scharfe
2021-01-31  3:52       ` Derrick Stolee [this message]
2021-01-31 10:20         ` René Scharfe
2021-01-31  3:59     ` Derrick Stolee
2021-01-31 20:13       ` Derrick Stolee
2021-01-31 20:25       ` Junio C Hamano
2021-02-01  3:55         ` Derrick Stolee
2021-01-29 17:10   ` René Scharfe
2021-01-28 16:24 ` [PATCH 2/3] commit-reach: move compare_commits_by_gen Derrick Stolee via GitGitGadget
2021-01-28 16:24 ` [PATCH 3/3] commit-reach: use heuristic in remove_redundant() Derrick Stolee via GitGitGadget
2021-01-28 20:20 ` [PATCH 0/3] Speed up remove_redundant() Junio C Hamano
2021-02-01 12:47 ` [PATCH v2 0/5] " Derrick Stolee via GitGitGadget
2021-02-01 12:47   ` [PATCH v2 1/5] commit-reach: reduce requirements for remove_redundant() Derrick Stolee via GitGitGadget
2021-02-01 19:51     ` Junio C Hamano
2021-02-01 12:47   ` [PATCH v2 2/5] commit-reach: use one walk in remove_redundant() Derrick Stolee via GitGitGadget
2021-02-01 16:12     ` René Scharfe.
2021-02-01 16:31       ` Derrick Stolee
2021-02-01 12:47   ` [PATCH v2 3/5] commit-reach: move compare_commits_by_gen Derrick Stolee via GitGitGadget
2021-02-01 12:47   ` [PATCH v2 4/5] commit-reach: use heuristic in remove_redundant() Derrick Stolee via GitGitGadget
2021-02-01 20:05     ` Junio C Hamano
2021-02-01 21:02       ` Derrick Stolee
2021-02-01 12:47   ` [PATCH v2 5/5] commit-reach: stale commits may prune generation further Derrick Stolee via GitGitGadget
2021-02-03 15:59     ` Taylor Blau
2021-02-01 15:48   ` [PATCH v2 0/5] Speed up remove_redundant() Derrick Stolee
2021-02-18 23:25     ` Junio C Hamano
2021-02-19 12:17       ` Derrick Stolee
2021-02-20  3:32         ` Junio C Hamano
2021-02-19 12:34   ` [PATCH v3 " Derrick Stolee via GitGitGadget
2021-02-19 12:34     ` [PATCH v3 1/5] commit-reach: reduce requirements for remove_redundant() Derrick Stolee via GitGitGadget
2021-02-19 12:34     ` [PATCH v3 2/5] commit-reach: use one walk in remove_redundant() Derrick Stolee via GitGitGadget
2021-02-19 12:34     ` [PATCH v3 3/5] commit-reach: move compare_commits_by_gen Derrick Stolee via GitGitGadget
2021-02-19 12:34     ` [PATCH v3 4/5] commit-reach: use heuristic in remove_redundant() Derrick Stolee via GitGitGadget
2021-02-19 12:34     ` [PATCH v3 5/5] commit-reach: stale commits may prune generation further Derrick Stolee via GitGitGadget

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