From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, Elliott Cable <me@ell.io>
Subject: Re: [PATCH v2 2/4] commit-queue: LIFO or priority queue of commits
Date: Mon, 10 Jun 2013 00:21:00 -0700 [thread overview]
Message-ID: <7vwqq2l9cz.fsf@alter.siamese.dyndns.org> (raw)
In-Reply-To: <20130610052500.GD3621@sigill.intra.peff.net> (Jeff King's message of "Mon, 10 Jun 2013 01:25:00 -0400")
Jeff King <peff@peff.net> writes:
> It may be worth looking again for other places to use this over
> commit_list, but even the caller you are introducing here justifies its
> presence.
The next candidate is paint-down-to-common, probably.
> Also, I wrote some basic tests to cover the priority queue as a unit. I
> can rebase them on your commit if you are interested.
It would be great.
> A few comments on the code itself:
>
>> +void commit_queue_put(struct commit_queue *queue, struct commit *commit)
>
> Is it worth making this "struct commit *" a void pointer, and handling
> arbitrary items in our priority queue? The compare function should be
> the only thing that dereferences them.
>
> I do not have any non-commit priority queue use in mind, but I do not
> think it adds any complexity in this case.
I didn't either (and still I don't think of one), but I agree that
the implementation can be reused for pq of any type, as long as it
is a pointer to struct.
>> + /* Bubble up the new one */
>> + for (ix = queue->nr - 1; ix; ix = parent) {
>> + parent = (ix - 1) / 2;
>> + if (compare(queue->array[parent], queue->array[ix],
>> + queue->cb_data) < 0)
>> + break;
>
> In my implementation, I stopped on "compare() <= 0". It is late and my
> mind is fuzzy, but I recall that heaps are never stable with respect to
> insertion order, so I don't think it would matter.
It would matter in the sense that we cannot replace linked-list, if
the caller wants stability. It is more like "we cannot do anything
about it" than "it would not matter".
We can make each queue element a pair of <pointer to payload,
insertion counter>, and tiebreak using the insertion order, if the
callers want the same stability as linked-list implementation, but
I tend to think it really matters.
next prev parent reply other threads:[~2013-06-10 7:21 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-04 18:08 [PATCH/RFC] add --authorship-order flag to git log / rev-list elliottcable
2013-06-04 18:08 ` [PATCH/RFC] rev-list: add --authorship-order alternative ordering elliottcable
2013-06-04 19:14 ` Junio C Hamano
2013-06-04 21:20 ` Junio C Hamano
2013-06-06 19:03 ` Elliott Cable
2013-06-06 19:29 ` Junio C Hamano
2013-06-06 19:32 ` Elliott Cable
2013-06-06 19:40 ` Junio C Hamano
2013-06-06 22:48 ` Junio C Hamano
2013-06-06 23:25 ` [PATCH] toposort: rename "lifo" field Junio C Hamano
2013-06-07 1:25 ` Junio C Hamano
2013-06-07 5:11 ` [PATCH 0/3] Preparing for --date-order=author Junio C Hamano
2013-06-07 5:11 ` [PATCH 1/3] toposort: rename "lifo" field Junio C Hamano
2013-06-07 5:18 ` Eric Sunshine
2013-06-07 5:21 ` Junio C Hamano
2013-06-07 5:11 ` [PATCH 2/3] commit-queue: LIFO or priority queue of commits Junio C Hamano
2013-06-07 5:29 ` Eric Sunshine
2013-06-07 5:11 ` [PATCH 3/3] sort-in-topological-order: use commit-queue Junio C Hamano
2013-06-09 23:24 ` [PATCH v2 0/4] log --author-date-order Junio C Hamano
2013-06-09 23:24 ` [PATCH v2 1/4] toposort: rename "lifo" field Junio C Hamano
2013-06-10 2:12 ` Eric Sunshine
2013-06-10 5:05 ` Jeff King
2013-06-09 23:24 ` [PATCH v2 2/4] commit-queue: LIFO or priority queue of commits Junio C Hamano
2013-06-10 5:25 ` Jeff King
2013-06-10 7:21 ` Junio C Hamano [this message]
2013-06-10 18:15 ` Jeff King
2013-06-10 18:56 ` Junio C Hamano
2013-06-10 18:59 ` Jeff King
2013-06-10 23:23 ` Junio C Hamano
2013-06-11 6:36 ` Jeff King
2013-06-11 17:02 ` Junio C Hamano
2013-06-11 22:19 ` [PATCH v3 0/4] log --author-date-order Junio C Hamano
2013-06-11 22:19 ` [PATCH v3 1/4] toposort: rename "lifo" field Junio C Hamano
2013-06-11 22:19 ` [PATCH v3 2/4] prio-queue: priority queue of pointers to structs Junio C Hamano
2013-06-11 22:19 ` [PATCH v3 3/4] sort-in-topological-order: use prio-queue Junio C Hamano
2013-06-11 22:19 ` [PATCH v3 4/4] log: --author-date-order Junio C Hamano
2013-06-09 23:24 ` [PATCH v2 3/4] sort-in-topological-order: use commit-queue Junio C Hamano
2013-06-09 23:37 ` Junio C Hamano
2013-06-10 5:31 ` Jeff King
2013-06-10 7:27 ` Junio C Hamano
2013-06-10 18:24 ` Jeff King
2013-06-09 23:24 ` [PATCH v2 4/4] log: --author-date-order Junio C Hamano
2013-06-10 5:50 ` Jeff King
2013-06-10 7:39 ` Junio C Hamano
2013-06-10 18:49 ` Jeff King
2013-06-20 19:36 ` Junio C Hamano
2013-06-20 20:16 ` Jeff King
2013-06-07 5:09 ` [PATCH] toposort: rename "lifo" field Eric Sunshine
2013-06-04 21:22 ` [PATCH/RFC] rev-list: add --authorship-order alternative ordering Jeff King
2013-06-04 18:53 ` [PATCH/RFC] add --authorship-order flag to git log / rev-list Junio C Hamano
2013-06-06 18:06 ` Elliott Cable
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