Performance: voila takes double the time to create widgets compared to Notebook

[maartenbreddels]

Creating ~600 widgets using:

import ipywidgets as widgets
def recursive(n):
    if n == 0:
        return widgets.Button(description='Hi')
    else:
        cls = (widgets.VBox if n % 2 else widgets.HBox)
        return cls([recursive(n-1), recursive(n-1)])
recursive(7)

Takes about 1.5-2.0 seconds to display in the notebook, while it takes over 4.0 seconds using Voila.

I think at least one problem lies in the way we update the widgets / sync the state. We ask each widget/comm separately for an update, which causes a 'busy', 'update' and 'idle' message, 3x more than needed. This causes in total 1800 websocket messages. I am also not sure why that seems so slow.

[maartenbreddels]

jupyter/jupyter_client#590 takes off 50% of the time.
~2.8 to ~1.8 seconds

[maartenbreddels]

The 4 seconds mentioned above was with Chrome with the dev console open.

[maartenbreddels]

Minor contributor (few %): ipython/traitlets#638

[maartenbreddels]

tornadoweb/tornado#2955 is another 80msec per 1000 messages.

[maartenbreddels]

adding --Session.key= avoid signing of messages, which also takes off a few %.

[maartenbreddels]

jupyter-widgets/ipywidgets#3020
and
ipython/traitlets#639

scrape of 30%

[maartenbreddels]

A 5x improvement might be possible based on #766 and jupyter-widgets/ipywidgets#3021

[jtpio]

@maartenbreddels is this issue still valid with #933 now merged and released in 0.2.11?

[pierrotsmnrd]

Hi everyone,
I've tested this with Voilà 0.2.16 and I can confirm the issue is still valid. Rendering the snippet above with voilà is taking at least twice more time.

[martinRenou]

Things should be improved with the coming ipywidgets release and #766

[pierrotsmnrd]

Hi everyone :)
Any update on this issue and the next ipywidgets release ?
FYI I've tested again with Voilà 0.3.0 and the issue still occurs (logically)