Shuffling of large playlists is slow

[Uwe Klotz]

Shuffling of large playlists is slow as reported here:

http://www.mixxx.org/forums/viewtopic.php?f=3&t=8921

The poor performance is caused by repeatedly swapping the playlist's track positions directly in the database.

Proposal for an improved algorithm:
1) Read the ordered list of track positions from the database
2) Calculate a random permutation of these track positions in memory
3) Update the track positions in the database within a single pass

The proposed algorithm works even if the current positions are not numbered consecutively, which has been an issue in the past and should be taken into account.

[Nimit Bhardwaj (nimitbhardwaj)]

I take this bug, this bug seems to be an easy for me, I feel it interesting, i will try to solve it.

[Nimit Bhardwaj (nimitbhardwaj)]

Pull requested at https://github.com/mixxxdj/mixxx/pull/1205

[RJ Skerry-Ryan (rryan)]

Due to lack of progress, marking Triaged and clearing assignee. Feel
free to revert if it is in fact still in progress :).

[Gabriel Downs (gndowns)]

Is this still open? I'm new to mixxx, but it seems like the old PR could be fixed up to work.

[Daniel Schürmann (daschuer)]

It is currently closed, mainly because it has stalled.
If you like to continue the work I think it is a good idea to open a new one from the scratch and use the old one and the comments for inspiration.
Thank you in advance.

Did you now this page, by the way? https://www.mixxx.org/wiki/doku.php/bugfix_workflow

[Uwe Klotz (uklotzde-deactivatedaccount)]

The old PR didn't meet our quality requirements and was unfinished. I recommend starting a new approach at the current version.

[Gabriel Downs (gndowns)]

Ah I hadn't seen that page before, thank you! I'll check it all out

[Vladimír Dudr (vlada-dudr)]

I was working on this a little bit. It looks like it is shuffling only certain tracks in the playlist - why it is necessary to skip certain ones?

[Daniel Schürmann (daschuer)]

The shuffling is started here:
https://github.com/mixxxdj/mixxx/blob/9ea985dd613b4b34679888820f7367dd258f5447/src/library/autodj/autodjprocessor.cpp#L213

Only selected Tracks are shuffled. Is That the issue you experience?

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/8809