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From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Philip Oakley <philipoakley@iee.email>
Cc: Junio C Hamano <gitster@pobox.com>,
	Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org, Denton Liu <liu.denton@gmail.com>
Subject: Re: [PATCH v3 00/13] ci: include a Visual Studio build & test in our Azure Pipeline
Date: Thu, 10 Oct 2019 11:03:08 +0200 (CEST)	[thread overview]
Message-ID: <nycvar.QRO.7.76.6.1910101102280.46@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <9ccbdb9a-845f-a534-29b6-52cfe9eb3229@iee.email>

Hi Philip,

On Wed, 9 Oct 2019, Philip Oakley wrote:

> On 08/10/2019 13:46, Johannes Schindelin wrote:
> > Hi Junio,
> >
> > On Tue, 8 Oct 2019, Junio C Hamano wrote:
> >
> > > Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
> > >
> > > > > I didn't quite understand this part, though.
> > > > >
> > > > >      The default creation factor is 60 (roughly speaking, it wants 60%
> > > > >      of
> > > > >      the lines to match between two patches, otherwise it considers
> > > > >      the
> > > > >      patches to be unrelated).
> > > > >
> > > > > Would the updated creation factor used which is 95 (roughly
> > > > > speaking) want 95% of the lines to match between two patches?
> > > > >
> > > > > That would make the matching logic even pickier and reject more
> > > > > paring, so I must be reading the statement wrong X-<.
> > > > No, I must have written the opposite of what I tried to say, is all.
> > > So, cfactor of 60 means at most 60% is allowed to differ and the
> > > two patches are still considered to be related, while 95 means only
> > > 5% needs to be common?  That would make more sense to me.
> > Okay, I not only wrote the opposite of what I wanted to say, I also
> > misremembered.
> >
> > When `range-diff` tries to determine matching pairs of patches, it
> > builds an `(m+n)x(m+n)` cost matrix, where `m` is the number of patches
> > in the first commit range and `n` is the number of patches in the second
> > one.
> >
> > Why not `m x n`? Well, that's the obvious matrix, and that's what it
> > starts with, essentially assigning the number of lines of the diff
> > between the diffs as "cost".
> >
> > But then `git range-diff` extends the cost matrix to allow for _all_ of
> > the `m` patches to be considered deleted, and _all_ of the `n` patches
> > to be added. As cost, it cannot use a "diff of diffs" because there is
> > no second diff. So it uses the number of lines of the one diff it has,
> > multiplied by the creation factor interpreted as a percentage.
> >
> > The naive creation factor would be 100%, which is (almost) as if we
> > assumed an empty diff for the missing diff. But that would make the
> > range-diff too eager to dismiss rewrites, as experience obviously showed
> > (not my experience, but Thomas Rast's, who came up with `tbdiff` after
> > all): the diff of diffs includes a diff header, for example.
> >
> > The interpretation I offered (although I inverted what I wanted to say)
> > is similar in spirit to that metric (which is not actually a metric, I
> > believe, because I expect it to violate the triangle inequality) is
> > obviously inaccurate: the number of lines of the diff of diffs does not
> > say anything about the number of matching lines, quite to the contrary,
> > it correlates somewhat to the number of non-matching lines.
> >
> > So a better interpretation would have been:
> >
> >  The default creation factor is 60 (roughly speaking, it wants at
> >  most 60% of the diffs' lines to differ, otherwise it considers
> >  them not to be a match.
> >
> > This is still inaccurate, but at least it gets the idea of the
> > range-diff across.
> >
> > Of course, I will never be able to amend the commit message in
> > GitGitGadget anyway, as I have merged that PR already.
> >
> > Ciao,
> > Dscho
> Medium term, is this something that could go in the algorithms section of the
> range-diff man page, especially if the upstream commit message is already in
> place.
>
> #leftoverdocs ?

Sure. How about giving it a try while our memory is still fresh? You
would help me immensely if you could take that task off of my plate...

Thanks,
Dscho

  reply	other threads:[~2019-10-10  9:03 UTC|newest]

Thread overview: 72+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-26  8:30 [PATCH " Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 01/13] push: do not pretend to return `int` from `die_push_simple()` Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 02/13] msvc: avoid using minus operator on unsigned types Johannes Schindelin via GitGitGadget
2019-09-26 17:20   ` Denton Liu
2019-09-26 21:01     ` Johannes Schindelin
2019-09-26 23:57       ` Denton Liu
2019-09-30  9:50         ` Johannes Schindelin
2019-09-26  8:30 ` [PATCH 03/13] winansi: use FLEX_ARRAY to avoid compiler warning Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 04/13] compat/win32/path-utils.h: add #include guards Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 05/13] msvc: ignore some libraries when linking Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 06/13] msvc: handle DEVELOPER=1 Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 07/13] msvc: work around a bug in GetEnvironmentVariable() Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 08/13] vcxproj: only copy `git-remote-http.exe` once it was built Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 09/13] vcxproj: include more generated files Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 10/13] test-tool run-command: learn to run (parts of) the testsuite Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 11/13] tests: let --immediate and --write-junit-xml play well together Johannes Schindelin via GitGitGadget
2019-09-28 22:22   ` Junio C Hamano
2019-09-30  9:52     ` Johannes Schindelin
2019-09-26  8:30 ` [PATCH 12/13] ci: really use shallow clones on Azure Pipelines Johannes Schindelin via GitGitGadget
2019-09-26  8:30 ` [PATCH 13/13] ci: also build and test with MS Visual Studio " Johannes Schindelin via GitGitGadget
2019-09-30  9:55 ` [PATCH v2 00/13] ci: include a Visual Studio build & test in our Azure Pipeline Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 01/13] push: do not pretend to return `int` from `die_push_simple()` Johannes Schindelin via GitGitGadget
2019-10-03 22:37     ` Junio C Hamano
2019-10-04  9:36       ` Johannes Schindelin
2019-09-30  9:55   ` [PATCH v2 02/13] msvc: avoid using minus operator on unsigned types Johannes Schindelin via GitGitGadget
2019-10-03 22:44     ` Junio C Hamano
2019-10-04  9:55       ` Johannes Schindelin
2019-10-04 17:09         ` Johannes Sixt
2019-10-04 21:24           ` Johannes Schindelin
2019-10-06  0:02             ` Junio C Hamano
2019-10-06 10:53               ` Johannes Sixt
2019-10-08 12:04                 ` Johannes Schindelin
2019-10-08 21:13                   ` Johannes Sixt
2019-09-30  9:55   ` [PATCH v2 03/13] winansi: use FLEX_ARRAY to avoid compiler warning Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 04/13] compat/win32/path-utils.h: add #include guards Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 05/13] msvc: ignore some libraries when linking Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 06/13] msvc: handle DEVELOPER=1 Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 07/13] msvc: work around a bug in GetEnvironmentVariable() Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 09/13] vcxproj: include more generated files Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 08/13] vcxproj: only copy `git-remote-http.exe` once it was built Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 10/13] test-tool run-command: learn to run (parts of) the testsuite Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 11/13] tests: let --immediate and --write-junit-xml play well together Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 12/13] ci: really use shallow clones on Azure Pipelines Johannes Schindelin via GitGitGadget
2019-09-30  9:55   ` [PATCH v2 13/13] ci: also build and test with MS Visual Studio " Johannes Schindelin via GitGitGadget
2019-10-04 15:09   ` [PATCH v3 00/13] ci: include a Visual Studio build & test in our Azure Pipeline Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 01/13] push: do not pretend to return `int` from `die_push_simple()` Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 02/13] msvc: avoid using minus operator on unsigned types Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 03/13] winansi: use FLEX_ARRAY to avoid compiler warning Johannes Schindelin via GitGitGadget
2019-10-07 19:16       ` Alban Gruin
2019-10-04 15:09     ` [PATCH v3 04/13] compat/win32/path-utils.h: add #include guards Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 05/13] msvc: ignore some libraries when linking Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 07/13] msvc: work around a bug in GetEnvironmentVariable() Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 06/13] msvc: handle DEVELOPER=1 Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 08/13] vcxproj: only copy `git-remote-http.exe` once it was built Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 09/13] vcxproj: include more generated files Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 10/13] test-tool run-command: learn to run (parts of) the testsuite Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 11/13] tests: let --immediate and --write-junit-xml play well together Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 12/13] ci: really use shallow clones on Azure Pipelines Johannes Schindelin via GitGitGadget
2019-10-04 15:09     ` [PATCH v3 13/13] ci: also build and test with MS Visual Studio " Johannes Schindelin via GitGitGadget
2019-10-06  0:19     ` [PATCH v3 00/13] ci: include a Visual Studio build & test in our Azure Pipeline Junio C Hamano
2019-10-06 10:45       ` Johannes Schindelin
2019-10-06 20:38         ` Johannes Schindelin
2019-10-07  1:14           ` Junio C Hamano
2019-10-07 21:51             ` Johannes Schindelin
2019-10-08  2:19               ` Junio C Hamano
2019-10-08 12:46                 ` Johannes Schindelin
2019-10-09 13:57                   ` Philip Oakley
2019-10-10  9:03                     ` Johannes Schindelin [this message]
2019-10-10 10:12                       ` Philip Oakley
2019-10-07  0:59         ` Junio C Hamano
2019-10-07 16:08           ` Thomas Gummerer
2019-10-11 22:06             ` Johannes Schindelin

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