From: Abhradeep Chakraborty <chakrabortyabhradeep79@gmail.com>
To: Taylor Blau <me@ttaylorr.com>
Cc: Abhradeep Chakraborty via GitGitGadget <gitgitgadget@gmail.com>,
git <git@vger.kernel.org>,
Kaartic Sivaram <kaartic.sivaraam@gmail.com>,
Derrick Stolee <derrickstolee@github.com>
Subject: Re: [PATCH v3 2/6] pack-bitmap-write.c: write lookup table extension
Date: Fri, 15 Jul 2022 21:28:25 +0530 [thread overview]
Message-ID: <CAPOJW5x8Vf2qJ-109UH=gvy2i7HdfbFH84hb6fD+YUBN4-GkRg@mail.gmail.com> (raw)
In-Reply-To: <YtDPePTo52A+Uo0p@nand.local>
On Fri, Jul 15, 2022 at 7:52 AM Taylor Blau <me@ttaylorr.com> wrote:
>
> By the end of this loop, we have an array `commit_positions` which maps
> the ith selected commit to its lexical position among all objects in the
> bitmap. IOW, `commit_positions[i] = j` means the `i`th selected commit
> can be found at index `j` among all objects in the pack/MIDX in their
> lexical order.
Right.
> > + /*
> > + * At the end of this sort table[j] = i means that the i'th
> > + * bitmap corresponds to j'th bitmapped commit in lex order of
> > + * OIDs.
> > + */
> > + QSORT_S(table, writer.selected_nr, table_cmp, commit_positions);
>
> And then we sort table by treating its values as indexes into
> `commit_positions`. Here's where I'm not sure that I follow what's going
> on. You say above that `table[j] = i`, where `i` corresponds to the
> order of selected commits, and `j` is in lexical order.
Correct.
> If that's the case, then I'd expect that printing `index[table[j]]` for
> increasing `j` would output OIDs in increasing lexical order. But that
> doesn't quite seem to be the case. From a debugger session that has a
> breakpoint after computing and sorting table, along with building
> `table_inv`:
>
> (gdb) p oid_to_hex(&index[table[0]]->oid)
> $17 = 0x555555983ea0 <hexbuffer> "0006763074748d43b539c1c8e8882c08034ab178"
> (gdb) p oid_to_hex(&index[table[1]]->oid)
> $18 = 0x555555983ee1 <hexbuffer+65> "001ce83dd43f03dcfc67f29d38922e4a9682aab0"
> (gdb) p oid_to_hex(&index[table[2]]->oid)
> $19 = 0x555555983f22 <hexbuffer+130> "002db882ece2ab6a240e495a169c6e06422289c8"
> (gdb) p oid_to_hex(&index[table[3]]->oid)
> $20 = 0x555555983f63 <hexbuffer+195> "0007a5feb040e1ff704f3ad636619ddca3e7382b"
>
> that doesn't look like the OIDs are increasing in lexical order.
>
> I'm not quite sure if I'm even looking at the right thing, or if this is
> to be expected, or if the comment isn't quite accurate. If you could
> help clarify what's going on here, that would be great.
I think you're not looking at the right thing. you should look at
`writer.selected[table[i]].commit->object.oid` instead. I think the
order of `index[]`
is not the same as the pack index (or midx).
I am saying this because if we use the `pos` variable (that we get
from `commit_bitmap_writer_pos(&writer.selected[table[i]].commit->object.oid,
index, index_nr)`) in `fprintf(stderr, "commit hex: %s\n",
&index[pos]->oid);`, you'll see that `&index[pos]->oid` and
`&writer.selected[table[i]].commit->object.oid` are not same. So, If
you do -
int spos = commit_bitmap_writer_pos(&index[pos]->oid, index, index_nr);
you'll see `spos` is not equal to `pos`.
> > + /* table_inv helps us discover that relationship (i'th bitmap
> > + * to j'th commit by j = table_inv[i])
> > + */
> > + for (i = 0; i < writer.selected_nr; i++)
> > + table_inv[table[i]] = i;
>
> This part makes sense, as does the rest of the implementation.
>
> Thanks,
> Taylor
next prev parent reply other threads:[~2022-07-15 15:58 UTC|newest]
Thread overview: 162+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-20 12:33 [PATCH 0/6] [GSoC] bitmap: integrate a lookup table extension to the bitmap format Abhradeep Chakraborty via GitGitGadget
2022-06-20 12:33 ` [PATCH 1/6] Documentation/technical: describe bitmap lookup table extension Abhradeep Chakraborty via GitGitGadget
2022-06-20 16:56 ` Derrick Stolee
2022-06-20 17:09 ` Taylor Blau
2022-06-21 8:31 ` Abhradeep Chakraborty
2022-06-22 16:26 ` Taylor Blau
2022-06-21 8:23 ` Abhradeep Chakraborty
2022-06-20 17:21 ` Taylor Blau
2022-06-21 9:22 ` Abhradeep Chakraborty
2022-06-22 16:29 ` Taylor Blau
2022-06-22 16:45 ` Abhradeep Chakraborty
2022-06-20 20:21 ` Derrick Stolee
2022-06-21 10:08 ` Abhradeep Chakraborty
2022-06-22 16:30 ` Taylor Blau
2022-06-20 12:33 ` [PATCH 2/6] pack-bitmap: prepare to read " Abhradeep Chakraborty via GitGitGadget
2022-06-20 20:49 ` Derrick Stolee
2022-06-21 10:28 ` Abhradeep Chakraborty
2022-06-20 22:06 ` Taylor Blau
2022-06-21 11:52 ` Abhradeep Chakraborty
2022-06-22 16:49 ` Taylor Blau
2022-06-22 17:18 ` Abhradeep Chakraborty
2022-06-22 21:34 ` Taylor Blau
2022-06-20 12:33 ` [PATCH 3/6] pack-bitmap-write.c: write " Abhradeep Chakraborty via GitGitGadget
2022-06-20 22:16 ` Taylor Blau
2022-06-21 12:50 ` Abhradeep Chakraborty
2022-06-22 16:51 ` Taylor Blau
2022-06-20 12:33 ` [PATCH 4/6] builtin/pack-objects.c: learn pack.writeBitmapLookupTable Taylor Blau via GitGitGadget
2022-06-20 22:18 ` Taylor Blau
2022-06-20 12:33 ` [PATCH 5/6] bitmap-commit-table: add tests for the bitmap lookup table Abhradeep Chakraborty via GitGitGadget
2022-06-22 16:54 ` Taylor Blau
2022-06-20 12:33 ` [PATCH 6/6] bitmap-lookup-table: add performance tests Abhradeep Chakraborty via GitGitGadget
2022-06-22 17:14 ` Taylor Blau
2022-06-26 13:10 ` [PATCH v2 0/6] [GSoC] bitmap: integrate a lookup table extension to the bitmap format Abhradeep Chakraborty via GitGitGadget
2022-06-26 13:10 ` [PATCH v2 1/6] Documentation/technical: describe bitmap lookup table extension Abhradeep Chakraborty via GitGitGadget
2022-06-27 14:18 ` Derrick Stolee
2022-06-27 15:48 ` Taylor Blau
2022-06-27 16:51 ` Abhradeep Chakraborty
2022-06-26 13:10 ` [PATCH v2 2/6] pack-bitmap-write.c: write " Abhradeep Chakraborty via GitGitGadget
2022-06-27 14:35 ` Derrick Stolee
2022-06-27 16:12 ` Taylor Blau
2022-06-27 17:10 ` Abhradeep Chakraborty
2022-06-27 16:05 ` Taylor Blau
2022-06-27 18:29 ` Abhradeep Chakraborty
2022-06-26 13:10 ` [PATCH v2 3/6] pack-bitmap-write: learn pack.writeBitmapLookupTable and add tests Abhradeep Chakraborty via GitGitGadget
2022-06-27 14:43 ` Derrick Stolee
2022-06-27 17:42 ` Abhradeep Chakraborty
2022-06-27 17:49 ` Taylor Blau
2022-06-27 17:47 ` Taylor Blau
2022-06-27 18:39 ` Abhradeep Chakraborty
2022-06-29 20:11 ` Taylor Blau
2022-06-26 13:10 ` [PATCH v2 4/6] pack-bitmap: prepare to read lookup table extension Abhradeep Chakraborty via GitGitGadget
2022-06-27 15:12 ` Derrick Stolee
2022-06-27 18:06 ` [PATCH v2 4/6] pack-bitmap: prepare to read lookup table Abhradeep Chakraborty
2022-06-27 18:32 ` Derrick Stolee
2022-06-27 21:49 ` [PATCH v2 4/6] pack-bitmap: prepare to read lookup table extension Taylor Blau
2022-06-28 8:59 ` [PATCH v2 4/6] pack-bitmap: prepare to read lookup table Abhradeep Chakraborty
2022-06-29 20:22 ` Taylor Blau
2022-06-30 6:58 ` [PATCH v2 4/6] pack-bitmap: prepare to read lookup table extension Abhradeep Chakraborty
2022-06-27 21:38 ` Taylor Blau
2022-06-28 19:25 ` Abhradeep Chakraborty
2022-06-29 20:37 ` Taylor Blau
2022-06-29 20:41 ` Taylor Blau
2022-06-30 8:35 ` Abhradeep Chakraborty
2022-06-26 13:10 ` [PATCH v2 5/6] bitmap-lookup-table: add performance tests for lookup table Abhradeep Chakraborty via GitGitGadget
2022-06-27 21:53 ` Taylor Blau
2022-06-28 7:58 ` Abhradeep Chakraborty
2022-06-29 20:40 ` Taylor Blau
2022-06-26 13:10 ` [PATCH v2 6/6] p5310-pack-bitmaps.sh: enable pack.writeReverseIndex for testing Abhradeep Chakraborty via GitGitGadget
2022-06-27 21:50 ` Taylor Blau
2022-06-28 8:01 ` Abhradeep Chakraborty
2022-07-04 8:46 ` [PATCH v3 0/6] [GSoC] bitmap: integrate a lookup table extension to the bitmap format Abhradeep Chakraborty via GitGitGadget
2022-07-04 8:46 ` [PATCH v3 1/6] Documentation/technical: describe bitmap lookup table extension Abhradeep Chakraborty via GitGitGadget
2022-07-08 16:38 ` Philip Oakley
2022-07-09 7:53 ` Abhradeep Chakraborty
2022-07-10 15:01 ` Philip Oakley
2022-07-14 23:15 ` Taylor Blau
2022-07-15 10:36 ` Philip Oakley
2022-07-15 18:48 ` Abhradeep Chakraborty
2022-07-04 8:46 ` [PATCH v3 2/6] pack-bitmap-write.c: write " Abhradeep Chakraborty via GitGitGadget
2022-07-14 23:26 ` Taylor Blau
2022-07-15 2:22 ` Taylor Blau
2022-07-15 15:58 ` Abhradeep Chakraborty [this message]
2022-07-15 22:15 ` Taylor Blau
2022-07-16 11:50 ` Abhradeep Chakraborty
2022-07-26 0:34 ` Taylor Blau
2022-07-18 8:59 ` Martin Ågren
2022-07-04 8:46 ` [PATCH v3 3/6] pack-bitmap-write: learn pack.writeBitmapLookupTable and add tests Abhradeep Chakraborty via GitGitGadget
2022-07-04 8:46 ` [PATCH v3 4/6] pack-bitmap: prepare to read lookup table extension Abhradeep Chakraborty via GitGitGadget
2022-07-15 2:46 ` Taylor Blau
2022-07-15 16:38 ` Abhradeep Chakraborty
2022-07-15 22:20 ` Taylor Blau
2022-07-18 9:06 ` Martin Ågren
2022-07-18 19:25 ` Abhradeep Chakraborty
2022-07-18 23:26 ` Martin Ågren
2022-07-26 0:45 ` Taylor Blau
2022-07-04 8:46 ` [PATCH v3 5/6] bitmap-lookup-table: add performance tests for lookup table Abhradeep Chakraborty via GitGitGadget
2022-07-15 2:53 ` Taylor Blau
2022-07-15 18:23 ` Abhradeep Chakraborty
2022-07-04 8:46 ` [PATCH v3 6/6] p5310-pack-bitmaps.sh: remove pack.writeReverseIndex Abhradeep Chakraborty via GitGitGadget
2022-07-04 16:35 ` [PATCH v3 0/6] [GSoC] bitmap: integrate a lookup table extension to the bitmap format Abhradeep Chakraborty
2022-07-06 19:21 ` Junio C Hamano
2022-07-07 8:48 ` Abhradeep Chakraborty
2022-07-07 18:09 ` Kaartic Sivaraam
2022-07-07 18:42 ` Abhradeep Chakraborty
2022-07-20 14:05 ` [PATCH v4 " Abhradeep Chakraborty via GitGitGadget
2022-07-20 14:05 ` [PATCH v4 1/6] Documentation/technical: describe bitmap lookup table extension Abhradeep Chakraborty via GitGitGadget
2022-07-20 14:05 ` [PATCH v4 2/6] pack-bitmap-write.c: write " Abhradeep Chakraborty via GitGitGadget
2022-07-20 14:05 ` [PATCH v4 3/6] pack-bitmap-write: learn pack.writeBitmapLookupTable and add tests Abhradeep Chakraborty via GitGitGadget
2022-07-20 14:05 ` [PATCH v4 4/6] pack-bitmap: prepare to read lookup table extension Abhradeep Chakraborty via GitGitGadget
2022-07-20 14:05 ` [PATCH v4 5/6] p5310-pack-bitmaps.sh: enable `pack.writeReverseIndex` Abhradeep Chakraborty via GitGitGadget
2022-07-20 14:05 ` [PATCH v4 6/6] bitmap-lookup-table: add performance tests for lookup table Abhradeep Chakraborty via GitGitGadget
2022-07-20 18:38 ` [PATCH v5 0/6] [GSoC] bitmap: integrate a lookup table extension to the bitmap format Abhradeep Chakraborty via GitGitGadget
2022-07-20 18:38 ` [PATCH v5 1/6] Documentation/technical: describe bitmap lookup table extension Abhradeep Chakraborty via GitGitGadget
2022-07-20 18:38 ` [PATCH v5 2/6] pack-bitmap-write.c: write " Abhradeep Chakraborty via GitGitGadget
2022-07-26 0:52 ` Taylor Blau
2022-07-26 18:22 ` Abhradeep Chakraborty
2022-07-20 18:38 ` [PATCH v5 3/6] pack-bitmap-write: learn pack.writeBitmapLookupTable and add tests Abhradeep Chakraborty via GitGitGadget
2022-07-28 19:22 ` Johannes Schindelin
2022-08-02 12:40 ` Abhradeep Chakraborty
2022-08-02 15:35 ` Johannes Schindelin
2022-08-02 17:44 ` Abhradeep Chakraborty
2022-08-08 13:06 ` Johannes Schindelin
2022-08-08 13:58 ` Abhradeep Chakraborty
2022-08-09 9:03 ` Johannes Schindelin
2022-08-09 12:03 ` Abhradeep Chakraborty
2022-08-09 12:07 ` Abhradeep Chakraborty
2022-08-10 9:09 ` Johannes Schindelin
2022-08-10 9:20 ` Johannes Schindelin
2022-08-10 10:04 ` Abhradeep Chakraborty
2022-08-10 17:51 ` Derrick Stolee
2022-08-12 18:51 ` Abhradeep Chakraborty
2022-08-12 19:22 ` Derrick Stolee
2022-08-13 10:59 ` Abhradeep Chakraborty
2022-08-16 21:57 ` Taylor Blau
2022-08-17 10:02 ` Abhradeep Chakraborty
2022-08-17 20:38 ` Taylor Blau
2022-08-19 21:49 ` Taylor Blau
2022-08-13 11:05 ` Abhradeep Chakraborty
2022-08-16 18:47 ` Taylor Blau
2022-07-20 18:38 ` [PATCH v5 4/6] pack-bitmap: prepare to read lookup table extension Abhradeep Chakraborty via GitGitGadget
2022-07-26 1:13 ` Taylor Blau
2022-07-26 18:56 ` Abhradeep Chakraborty
2022-07-26 19:36 ` Eric Sunshine
2022-07-20 18:38 ` [PATCH v5 5/6] p5310-pack-bitmaps.sh: enable `pack.writeReverseIndex` Abhradeep Chakraborty via GitGitGadget
2022-07-26 1:18 ` Taylor Blau
2022-07-26 7:15 ` Ævar Arnfjörð Bjarmason
2022-07-26 13:32 ` Derrick Stolee
2022-07-26 13:54 ` Ævar Arnfjörð Bjarmason
2022-07-26 18:17 ` Abhradeep Chakraborty
2022-07-20 18:38 ` [PATCH v5 6/6] bitmap-lookup-table: add performance tests for lookup table Abhradeep Chakraborty via GitGitGadget
2022-08-14 16:55 ` [PATCH v6 0/6] [GSoC] bitmap: integrate a lookup table extension to the bitmap format Abhradeep Chakraborty via GitGitGadget
2022-08-14 16:55 ` [PATCH v6 1/6] Documentation/technical: describe bitmap lookup table extension Abhradeep Chakraborty via GitGitGadget
2022-08-14 16:55 ` [PATCH v6 2/6] bitmap: move `get commit positions` code to `bitmap_writer_finish` Abhradeep Chakraborty via GitGitGadget
2022-08-14 16:55 ` [PATCH v6 3/6] pack-bitmap-write.c: write lookup table extension Abhradeep Chakraborty via GitGitGadget
2022-08-14 16:55 ` [PATCH v6 4/6] pack-bitmap-write: learn pack.writeBitmapLookupTable and add tests Abhradeep Chakraborty via GitGitGadget
2022-08-14 16:55 ` [PATCH v6 5/6] pack-bitmap: prepare to read lookup table extension Abhradeep Chakraborty via GitGitGadget
2022-08-14 16:55 ` [PATCH v6 6/6] bitmap-lookup-table: add performance tests for lookup table Abhradeep Chakraborty via GitGitGadget
2022-08-19 21:21 ` [PATCH v6 0/6] [GSoC] bitmap: integrate a lookup table extension to the bitmap format Junio C Hamano
2022-08-22 14:42 ` Johannes Schindelin
2022-08-22 14:48 ` Taylor Blau
2022-08-25 22:16 ` Taylor Blau
2022-08-26 16:02 ` Junio C Hamano
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