#metabrainz

aerozol: sure, I’ll look into it for you.

yellowhatpro: definitely, you can also coordinate with aerozol in case you need some help finalising the post

ansh: I accepted your changes to the PR, was there anything else I should do? Otherwise feel free to put it through!

Thanks aerozol. Now the PR is ready for merge :)

Is it just me or does this certificate looks forged for some reason https://usercontent.irccloud-cdn.com/file/SYTKN...

The logos aren't even placed properly :(

hello

chinmay: oh i see. will fix.

mayhem: alastairp: monkey: do we have a LB meeting later today?

std meeting time, yes?

sounds good, thanks

alastairp: Good morning!

hi Pratha-Fish, how are you?

I am doing well!

The track-MBID checking stuff is going fine too :)

However I've ran into a bottleneck

great, do you have code for that available now?

Yep

Hello everyone :)

However, it's taking ~18s to check 1 single file!

👍

that's just not feasable for the whole MLHD

outsidecontext, zas: Which time will we meet today?

no, that sounds quite slow. however we were testing thousands of files in only 30 seconds or so, right?

were you able to benchmark which part was slow? loading/checking/saving?

Yes, currently the checking part is the slowest

I even crosschecked the numbers with our previous tests and it looks just right

OK, let's take a look at the code then

right

Here's the code

almost all the elements are ready to be assembled. It's in a jupyter notebook right now for testing, etc

Ah I see

This code isn't working with unique MBIDs!

skelly37, outsidecontext : hey, what about usual meeting time?

ok, works for me

Pratha-Fish: hm, right. but you're right that this still seems to be much longer than I'd expect

That's right

Thankfully I've just realized a few optimizations here

i.e. Taking only unique rows

Fine for me

I'm loading and running the code now to see if I can recommend something

alastairp: The other faster optimization is just logging the "recording-MBID" that was marked as a track-MBID.

It's more complicated under the hood than it sounds actually

sure

atj: I'd like we progress on ansible crowdsec stuff, what about deploying it on rex & rudi to experiment and improve?

Pratha-Fish: just to check - `df_test_positive` is a sample dataframe that you created that includes some track ids and some track redirects, so that you can test the method?

alastairp: yes that's right

ok, great

Pratha-Fish: it looks to me like this specific pandas operation is really inefficient and we should target it

exactly

the first thing that I'd think of in this case is to just use a basic loop + counter. take a look at this:

run that and see how long it takes

on it

Nice that took 11s

did you run that in a single cell?

yes

put it in 2 - converting the track gids to a set only has to be done once

oh right

This time, let's also try doing it on both MB_track and MB_track_redir

All right, so plain python test is taking 11s for set conversion, and 300microseconds for the test!

mmmhm

* For both MB_track and MB_track_redir

so, in one way I'm surprised that the "typical" way that you might do it in pandas is so slow

It's probably due to the massive conversion overhead in pandas!

but it's also important to work out what our goal is - we could generate the intersection of the 2 dataframes and save it, but we could also do this in 2 phases - 1) quickly look at all items and then if we see something, 2) save the filename for further analysis

my guess is because both of these dataframes in pandas are lists

try `track_mbid_list = MB_track.gid.tolist()` and use `if recid in track_mbid_list:` instead

alastairp: Yes, that's exactly how I am logging the anomalies

Only the suspected MBID, and it's file path

and you'll see that this kind of check against a list is _way_ slower

Python sets for the win!

well, keep in mind that this is "datastructures for the win", using the correct tool for the job

this is O-notation, if you've covered it before in classes

Yes I am aware of it

Now I see why DSA is so important in interviews

I just tested `if recid in track_mbid_list:` on the 6 item dataset, and it took about 16 seconds

Looks like py set datastructure is implemented on hashmaps. Probably the biggest reason for these ridiculous lookup speeds

that's really close to the 20 that we saw with pandas

right

I also modified my pandas code a little, and it's taking ~14s now

yes, right. when you have a list [1,2,3,4,5,6] and you want to check `if 8 in mylist` then it has to look at each item in the list. if it's not in the list you have to go through the entire list every single time you check

whereas with a hashed datastructure like a set (python dictionary keys work the same way), its just a hash operation + 1 lookup

O(1) vs O(n)

!!!

I still have one doubt though

This old code with pandas took only 2.89s for 381k (unique) rows https://usercontent.irccloud-cdn.com/file/khxUq...

Pratha-Fish: looks like there may be some efficient pandas methods here too: https://stackoverflow.com/a/21175114

alastairp: Wow that one looks fast

Let's try out the intersection method. It's written in numpy, so it's gotta be pretty fast for such a basic operation

note that in that microbenchmark it's still faster to convert the series to a set, do the intersection, turn it back into a python list, and then turn that into a Series again (the first item, almost 10% faster than the last one)

.intersection is a python set method

.intersect1d is a numpy method

right, so the method with set is still gonna be faster I assume

sure, it'd be good to take a look at them

one other thing that I noticed - after you select the data from the database, they are a UUID object:

> array([UUID('9b02977e-a03b-4a6b-a9a9-06e722bdcd7a'),

and it looks like this object has an "equality" method to compare other UUID objects and strings of UUIDs, but it looks like it's faster if we just treat them as strings

mayhem: hi! by any chance, do we have extra MeB tshirts available at office? :)

alastairp: yes, I noticed that one too.

I also tried explicitly loading MLHD data with all UUID columns specified as string

But somehow it gets converted into UUID along the way

O’Moin

I am beyond surprised https://usercontent.irccloud-cdn.com/file/MLvSh...

Pratha-Fish: psycopg2/postgres does this if you select an item which is a uuid column

lucifer: yes. Let me check sizes. But we'll be making more for the summit, right monkey?

you can force this to text if you do `SELECT gid::text FROM recording`

awesome! :DD

alastairp: oh yes, that's probably the reason here

Pratha-Fish: OK, I just benchmarked using a UUID object and a string and the difference isn't actually as much as I expected. probably not a big issue

object: 3.06 ms ± 12.1 µs per loop

string: 3.03 ms ± 7.64 µs per loop

Alright

alastairp: Hi! I had reviewed CB#442 and now it's ready for merge.

Adding Guidelines and link to CoC: https://github.com/metabrainz/critiquebrainz/pu...

ansh: I saw that, thank you so much!

ansh: I'll also take a look at your search PR again, and the other API ones you added (you need the metadata and rating one for BB integration, right?)

yes

It was really great reviewing a PR :) Thank you for this opportunity

great, I'm glad that you enjoyed it!