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From: Junio C Hamano <gitster@pobox.com>
To: karthik nayak <karthik.188@gmail.com>
Cc: Jonathan Tan via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org,  johannes.schindelin@gmx.de,  peff@peff.net,
	ps@pks.im,  me@ttaylorr.com,  johncai86@gmail.com,
	 newren@gmail.com, Derrick Stolee <stolee@gmail.com>,
	 Jonathan Tan <jonathantanmy@google.com>
Subject: Re: [PATCH v2 1/8] pack-objects: create new name-hash function version
Date: Thu, 05 Dec 2024 06:05:04 +0900	[thread overview]
Message-ID: <xmqqbjxr2m7z.fsf@gitster.g> (raw)
In-Reply-To: <CAOLa=ZRTgJafxDTB_LWGJxGZ_YOP4fO3=s14BHNvPaHEqf4Q_A@mail.gmail.com> (karthik nayak's message of "Wed, 4 Dec 2024 20:06:48 +0000")

karthik nayak <karthik.188@gmail.com> writes:

> 2. Generally in hashing algorithms the XOR is used to ensure that the
> output distribution is uniform which reduces collisions. Here, as you
> noted, we're more finding values for sorting rather than hashing in the
> traditional sense. So why use an XOR?

I am not Jonathan, but since the mixing-of-bits is done with XOR in
the original that Linus and I wrote, I think the question applies to
our version as well.  We prefer not to lose entropy from input
bytes, so we do not want to use OR or AND, which tend to paint
everything with 1 or 0 as you mix in bits from more bytes.

Anyway the question sounds like "generally when you take tests you
write with a pencil, but right now you are merely taking notes and
not taking any tests. why are you writing with a pencil?"  There are
multiple occasions that a pencil is a great fit as writing equipment.

  reply	other threads:[~2024-12-04 21:05 UTC|newest]

Thread overview: 93+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-11-05  3:05 [PATCH 0/7] pack-objects: Create an alternative name hash algorithm (recreated) Derrick Stolee via GitGitGadget
2024-11-05  3:05 ` [PATCH 1/7] pack-objects: add --full-name-hash option Derrick Stolee via GitGitGadget
2024-11-21 20:08   ` Taylor Blau
2024-11-21 21:35     ` Taylor Blau
2024-11-21 23:32       ` Junio C Hamano
2024-11-22 11:46       ` Derrick Stolee
2024-11-22 11:59     ` Derrick Stolee
2024-11-26  8:26   ` Patrick Steinhardt
2024-11-05  3:05 ` [PATCH 2/7] repack: " Derrick Stolee via GitGitGadget
2024-11-21 20:12   ` Taylor Blau
2024-11-22 12:07     ` Derrick Stolee
2024-11-05  3:05 ` [PATCH 3/7] pack-objects: add GIT_TEST_FULL_NAME_HASH Derrick Stolee via GitGitGadget
2024-11-21 20:15   ` Taylor Blau
2024-11-22 12:09     ` Derrick Stolee
2024-11-22  1:13   ` Jonathan Tan
2024-11-22  3:23     ` Junio C Hamano
2024-11-22 18:01       ` Jonathan Tan
2024-11-25  0:39         ` Junio C Hamano
2024-11-25 19:45           ` Jonathan Tan
2024-11-26  1:29             ` Junio C Hamano
2024-11-26  8:26   ` Patrick Steinhardt
2024-11-05  3:05 ` [PATCH 4/7] git-repack: update usage to match docs Derrick Stolee via GitGitGadget
2024-11-21 20:17   ` Taylor Blau
2024-11-22 15:26     ` Derrick Stolee
2024-11-05  3:05 ` [PATCH 5/7] p5313: add size comparison test Derrick Stolee via GitGitGadget
2024-11-21 20:31   ` Taylor Blau
2024-11-22 15:26     ` Derrick Stolee
2024-11-26  8:26   ` Patrick Steinhardt
2024-11-05  3:05 ` [PATCH 6/7] pack-objects: disable --full-name-hash when shallow Derrick Stolee via GitGitGadget
2024-11-21 20:33   ` Taylor Blau
2024-11-22 15:27     ` Derrick Stolee
2024-11-05  3:05 ` [PATCH 7/7] test-tool: add helper for name-hash values Derrick Stolee via GitGitGadget
2024-11-21 20:42   ` Taylor Blau
2024-11-22  1:23   ` Jonathan Tan
2024-11-21 23:50 ` [PATCH 0/7] pack-objects: Create an alternative name hash algorithm (recreated) Jonathan Tan
2024-11-22  3:01   ` Junio C Hamano
2024-11-22  4:22     ` Junio C Hamano
2024-11-22 15:27     ` Derrick Stolee
2024-11-24 23:57       ` Junio C Hamano
2024-11-22 18:05     ` Jonathan Tan
2024-12-02 23:21 ` [PATCH v2 0/8] " Derrick Stolee via GitGitGadget
2024-12-02 23:21   ` [PATCH v2 1/8] pack-objects: create new name-hash function version Jonathan Tan via GitGitGadget
2024-12-04 20:06     ` karthik nayak
2024-12-04 21:05       ` Junio C Hamano [this message]
2024-12-05  9:46         ` karthik nayak
2024-12-09 23:15     ` Jonathan Tan
2024-12-10  0:01       ` Junio C Hamano
2024-12-02 23:21   ` [PATCH v2 2/8] pack-objects: add --name-hash-version option Derrick Stolee via GitGitGadget
2024-12-04 20:53     ` karthik nayak
2024-12-02 23:21   ` [PATCH v2 3/8] repack: " Derrick Stolee via GitGitGadget
2024-12-04 21:15     ` karthik nayak
2024-12-02 23:21   ` [PATCH v2 4/8] pack-objects: add GIT_TEST_NAME_HASH_VERSION Derrick Stolee via GitGitGadget
2024-12-04 21:21     ` karthik nayak
2024-12-09 23:12     ` Jonathan Tan
2024-12-20 17:03       ` Derrick Stolee
2024-12-02 23:21   ` [PATCH v2 5/8] p5313: add size comparison test Derrick Stolee via GitGitGadget
2024-12-02 23:21   ` [PATCH v2 6/8] test-tool: add helper for name-hash values Derrick Stolee via GitGitGadget
2024-12-02 23:21   ` [PATCH v2 7/8] pack-objects: prevent name hash version change Derrick Stolee via GitGitGadget
2024-12-02 23:21   ` [PATCH v2 8/8] pack-objects: add third name hash version Derrick Stolee via GitGitGadget
2024-12-03  3:23   ` [PATCH v2 0/8] pack-objects: Create an alternative name hash algorithm (recreated) Junio C Hamano
2024-12-04  4:56     ` Derrick Stolee
2024-12-04  5:02       ` Junio C Hamano
2024-12-20 17:19   ` [PATCH v3 " Derrick Stolee via GitGitGadget
2024-12-20 17:19     ` [PATCH v3 1/8] pack-objects: create new name-hash function version Jonathan Tan via GitGitGadget
2025-01-22 22:08       ` Taylor Blau
2024-12-20 17:19     ` [PATCH v3 2/8] pack-objects: add --name-hash-version option Derrick Stolee via GitGitGadget
2025-01-22 22:17       ` Taylor Blau
2025-01-24 17:29         ` Derrick Stolee
2024-12-20 17:19     ` [PATCH v3 3/8] repack: " Derrick Stolee via GitGitGadget
2025-01-22 22:18       ` Taylor Blau
2024-12-20 17:19     ` [PATCH v3 4/8] pack-objects: add GIT_TEST_NAME_HASH_VERSION Derrick Stolee via GitGitGadget
2025-01-22 22:20       ` Taylor Blau
2024-12-20 17:19     ` [PATCH v3 5/8] p5313: add size comparison test Derrick Stolee via GitGitGadget
2024-12-20 17:19     ` [PATCH v3 6/8] test-tool: add helper for name-hash values Derrick Stolee via GitGitGadget
2024-12-20 17:19     ` [PATCH v3 7/8] pack-objects: prevent name hash version change Derrick Stolee via GitGitGadget
2025-01-22 22:22       ` Taylor Blau
2024-12-20 17:19     ` [PATCH v3 8/8] pack-objects: add third name hash version Derrick Stolee via GitGitGadget
2025-01-22 22:37       ` Taylor Blau
2025-01-24 17:34         ` Derrick Stolee
2025-01-21 20:21     ` [PATCH v3 0/8] pack-objects: Create an alternative name hash algorithm (recreated) Derrick Stolee
2025-01-22 23:28       ` Taylor Blau
2025-01-24 17:45         ` Derrick Stolee
2025-01-27 19:02     ` [PATCH v4 0/7] " Derrick Stolee via GitGitGadget
2025-01-27 19:02       ` [PATCH v4 1/7] pack-objects: create new name-hash function version Jonathan Tan via GitGitGadget
2025-01-27 19:02       ` [PATCH v4 2/7] pack-objects: add --name-hash-version option Derrick Stolee via GitGitGadget
2025-01-27 21:18         ` Junio C Hamano
2025-01-29 13:38           ` Derrick Stolee
2025-01-27 19:02       ` [PATCH v4 3/7] repack: " Derrick Stolee via GitGitGadget
2025-01-27 19:02       ` [PATCH v4 4/7] pack-objects: add GIT_TEST_NAME_HASH_VERSION Derrick Stolee via GitGitGadget
2025-01-27 19:02       ` [PATCH v4 5/7] p5313: add size comparison test Derrick Stolee via GitGitGadget
2025-01-27 19:02       ` [PATCH v4 6/7] test-tool: add helper for name-hash values Derrick Stolee via GitGitGadget
2025-01-27 19:02       ` [PATCH v4 7/7] pack-objects: prevent name hash version change Derrick Stolee via GitGitGadget
2025-01-31 21:39       ` [PATCH v4 0/7] pack-objects: Create an alternative name hash algorithm (recreated) Taylor Blau

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