[GSoC] Abhradeep's GSoC blogs (27 Jun, 2022 IST)

[GSoC] Abhradeep's GSoC blogs (27 Jun, 2022 IST)

[Abhradeep Chakraborty]

Hello developers, this is the thread where you can know about
my weekly GSoC blog links.

My Project - Reachability bitmap improvements

Blog update
------------

Title - GSoC Week 2: redesign the table format
Blog link - https://medium.com/@abhra303/gsoc-week-2-redesign-the-table-format-829dae755a5

Summary - 

In the last week, I worked on the reviews. Some major requested
changes are (1) Use commit positions instead of commit oids in
the table. (2) Use 8 byte offset positions instead of 4 bytes
(3) use iterative approach for parsing xor bitmaps (4) Use
`<commit_pos, offset, xor_pos>` triplets.

While implementing these changes, I discovered some bugs in the
previous version. I faced errors during this time. But finally
managed to fixed those errors. Taylor helped me to get rid of
some errors.

I think that we can optimise the parsing of xor bitmaps further
by stopping stack filling loop when we get an already parsed
bitmap since we know that bitmaps having xor relations with it
has already been stored/parsed.


Previous blogs 
---------------

------------------------------------------------------- 
Title - GSoC Week 1: Let's Get started
Blog link - https://medium.com/@abhra303/gsoc-week-1-lets-get-started-fad78ec34dcf

Summary -

This is the first blog that I wrote for GSoC. Taylor
suggested that I should work on "integrating a lookup table
extension" first as it is smaller compared to other sub-projects.

The idea is to have a table at the end of .bitmap file which
will contain the offsets (and xor-offsets) of the bitmaps of
selected commits. Whenever git try to get the bitmap of a
particular commit, instead of loading each bitmaps one by one,
git will parse only the desired bitmap by using the offset and
xor-offset of the table. This will reduce the overhead of
loading each and every bitmap.
-------------------------------------------------------

Re: [GSoC] Abhradeep's GSoC blogs (27 Jun, 2022 IST)

[Taylor Blau]

Hi Abhradeep,

On Mon, Jun 27, 2022 at 06:14:08PM +0530, Abhradeep Chakraborty wrote:
> Blog update
> ------------
>
> Title - GSoC Week 2: redesign the table format
> Blog link - https://medium.com/@abhra303/gsoc-week-2-redesign-the-table-format-829dae755a5

As usual, another great blog post! I think you did a nice job
summarizing the main discussion from reviewing the first round of your
patches.

You're exercising a good skill here, which is taking a big pile of
emails and figuring out what the main areas are that you need to
prioritize. That can be tricky, sometimes, since different reviewers
will tend to focus on different things, and may not even agree with each
other!

But I think you did a nice job teasing everything apart, and the v2 that
I've looked at already is a nice reflection of your work there.

I am glad that your work updating the series to the new format proved to
be an interesting challenge. I'm really happy with the result, so it was
definitely time well spent!

(One thing to keep in mind regarding the bug you fixed in `store_bitmap`
would be to ask why we weren't able to see that bug in CI. Assuming that
you encountered some other way, we should turn that into a test and make
sure that we don't regress there in the future).

Finally, your next steps sound interesting, and I'm looking forward to
seeing what you come up with! In the meantime, keep up the great work
:-).

Thanks,
Taylor