From: Michael Platings <michael@platin.gs>
To: Junio C Hamano <gitster@pobox.com>
Cc: "Barret Rhoden" <brho@google.com>,
"Git mailing list" <git@vger.kernel.org>,
"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
"David Kastrup" <dak@gnu.org>, "Jeff King" <peff@peff.net>,
"Jeff Smith" <whydoubt@gmail.com>,
"Johannes Schindelin" <Johannes.Schindelin@gmx.de>,
"René Scharfe" <l.s.r@web.de>,
"Stefan Beller" <stefanbeller@gmail.com>
Subject: Re: [PATCH v6 6/6] blame: use a fingerprint heuristic to match ignored lines
Date: Sun, 14 Apr 2019 10:41:26 +0100 [thread overview]
Message-ID: <CAJDYR9RHb89mjT65XVERJfo3cTySi++ZAwOFftBtyXkqfC=JOQ@mail.gmail.com> (raw)
In-Reply-To: <xmqqk1fxw8ad.fsf@gitster-ct.c.googlers.com>
> - I wonder if the hash used here can replace what is used in
> diffcore-delta.c as an improvement (or obviously vice versa), as
> using two (or more) ad-hoc fingerprinting function without having
> a clear reason why we need two instead of a unified one feels
> like a bad idea.
Hi Junio,
If I understand correctly, the algorithm in diffcore-delta.c is
intended to match files that contain identical lines (or 64-byte
chunks). The fingerprinting that Barret & I are talking about is
intended to match lines that contain identical byte pairs.
With significant refactoring, you could make the diffcore-delta
algorithm apply in both cases but I think the end result would be
longer and more complicated than keeping the two separate.
Unlike hashing a line, hashing a byte pair is trivial. Unlike hashing
lines, all except the first and last bytes are included in two
"hashes" - "hello" is hashed to "he", "el", "ll", "lo".
So based on my limited understanding of diffcore-delta.c I think the
two are algorithms are sufficiently different in intent and in
implementation that it's appropriate to keep them separate.
Regarding the "old heuristic" I think there may still be a use case
for that but I'll expand on that later.
Thanks,
-Michael
next prev parent reply other threads:[~2019-04-14 9:42 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-10 16:24 [PATCH v6 0/6] blame: add the ability to ignore commits Barret Rhoden
2019-04-10 16:24 ` [PATCH v6 1/6] Move init_skiplist() outside of fsck Barret Rhoden
2019-04-10 19:04 ` Ævar Arnfjörð Bjarmason
2019-04-15 13:32 ` Barret Rhoden
2019-04-10 16:24 ` [PATCH v6 2/6] blame: use a helper function in blame_chunk() Barret Rhoden
2019-04-10 16:24 ` [PATCH v6 3/6] blame: add the ability to ignore commits and their changes Barret Rhoden
2019-04-10 19:00 ` Ævar Arnfjörð Bjarmason
2019-04-14 10:42 ` Michael Platings
2019-04-15 13:32 ` Barret Rhoden
2019-04-15 13:34 ` Barret Rhoden
2019-04-10 16:24 ` [PATCH v6 4/6] blame: add config options to handle output for ignored lines Barret Rhoden
2019-04-14 3:45 ` Junio C Hamano
2019-04-14 10:09 ` Michael Platings
2019-04-14 10:24 ` Junio C Hamano
2019-04-14 11:27 ` Michael Platings
2019-04-15 13:51 ` Barret Rhoden
2019-04-10 16:24 ` [PATCH v6 5/6] blame: optionally track line fingerprints during fill_blame_origin() Barret Rhoden
2019-04-10 16:24 ` [PATCH v6 6/6] blame: use a fingerprint heuristic to match ignored lines Barret Rhoden
2019-04-14 3:54 ` Junio C Hamano
2019-04-14 9:41 ` Michael Platings [this message]
2019-04-15 14:03 ` Barret Rhoden
2019-04-16 4:10 ` Junio C Hamano
2019-04-14 21:10 ` [PATCH v6 0/6] blame: add the ability to ignore commits Michael Platings
2019-04-15 13:23 ` Barret Rhoden
2019-04-15 21:54 ` Michael Platings
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