From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 6/8] commit: provide a fast multi-tip contains function
Date: Thu, 26 Jun 2014 12:19:52 -0700 [thread overview]
Message-ID: <xmqqha374gx3.fsf@gitster.dls.corp.google.com> (raw)
In-Reply-To: <xmqqtx774i1r.fsf@gitster.dls.corp.google.com> (Junio C. Hamano's message of "Thu, 26 Jun 2014 11:55:28 -0700")
Junio C Hamano <gitster@pobox.com> writes:
> The only time you can say "Ah, we've seen this one and no need to
> dig further" is when you are propagating a colour C and the parent
> in question is already painted in C (it is OK to be painted as
> reachable from more tips), I would think, so shouldn't the loop be
> more like, after painting each tip and placing it in the queue:
>
> * Dequeue one, check the L/R bits in it and call that C
>
> * Iterate over its parents P:
>
> * check the L/R bits in P and call that Cp.
>
> * If Cp is already a superset of C, there is no point putting P
> to the queue to be processed.
>
> * If Cp is not a superset of C, then update L/R bits in P to mark
> it reachable from tips represented by C and put P to the queue.
>
> until you ran out of queue?
Actually that will cause you to dig down to the root, so it won't be
nice.
If you are trying to do "branch --with $commit", what you would want
is not exactly "paint-down-to-common(all branches, $commit)", but
something that paints down to $commit from all branches, with an
optimization that cuts off the traversal at a commit that is
reachable from $commit. If a traversal from branch B reached such a
commit that is reachable from $commit, you can stop the traversal
because propagating the bit for B further down to its parents will
not reach the $commit you are interested in.
So the termination condition for this a single Left (I'll use Left
for $commit and Right for "all branches") case is "if a commit is
already painted as reachable from $commit, do not propagate bits
further down".
What does it mean to look for "branch --with $commit1 $commit2"
(i.e. more than one in the Left set)? If we are trying to see which
branches reach _both_ of these commits, then replace the ablve with
"if a commit is already painted as reachable from both $commit{1,2},
then painting it with any branch bits is futile---its parents will
never reach either $commit1 nor $commit2", so the additional
termination condition will be "If left bits are full, then stop".
I do not know how you can optimize the traversal if you are trying
to see which branches reach at least one of these commits, though.
next prev parent reply other threads:[~2014-06-26 19:20 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-25 23:34 [PATCH 0/8] use merge-base for tag --contains Jeff King
2014-06-25 23:35 ` [PATCH 1/8] tag: allow --sort with -n Jeff King
2014-06-25 23:35 ` [PATCH 2/8] tag: factor out decision to stream tags Jeff King
2014-06-25 23:39 ` [PATCH 3/8] paint_down_to_common: use prio_queue Jeff King
2014-07-01 16:23 ` Junio C Hamano
2014-07-01 17:10 ` Jeff King
2014-06-25 23:40 ` [PATCH 4/8] add functions for memory-efficient bitmaps Jeff King
2014-06-26 3:15 ` Torsten Bögershausen
2014-06-26 15:51 ` Jeff King
2014-06-29 7:41 ` Eric Sunshine
2014-06-30 17:07 ` Jeff King
2014-07-01 16:57 ` Junio C Hamano
2014-07-01 17:18 ` Jeff King
2014-06-25 23:42 ` [PATCH 5/8] string-list: add pos to iterator callback Jeff King
2014-07-01 17:45 ` Junio C Hamano
2014-07-01 19:00 ` Jeff King
2014-06-25 23:47 ` [PATCH 6/8] commit: provide a fast multi-tip contains function Jeff King
2014-06-26 18:55 ` Junio C Hamano
2014-06-26 19:19 ` Junio C Hamano [this message]
2014-06-26 19:26 ` Junio C Hamano
2014-07-01 18:16 ` Junio C Hamano
2014-07-01 19:14 ` Junio C Hamano
2014-06-25 23:49 ` [PATCH 7/8] tag: use commit_contains Jeff King
2014-06-25 23:53 ` [PATCH 8/8] perf: add tests for tag --contains Jeff King
2014-06-26 0:01 ` Jeff King
2014-06-26 0:04 ` Jeff King
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