JSROOT hangs with TTree::Draw 0%

[sawenzel]

I am a big fan of JSROOT and in particular how it can be used to inspect ROOT data/histograms inside
Visual-Studio Code!

Generally, JSROOT works really well when trying to visualize small datasets. However, it seems that it has problems to treat even moderately large ROOT files or TTrees (say some 10MB compressed). Trying to draw a histogram from such files often leads to a hang with a TTree draw 0% message where no progress is visible/made for hours.

Is this something to be expected? Are there any hard limits or could the user do some tuning here?

ROOT Version: 6.28.02
JSROOT: version 7.2.0
Platform: Ubuntu 22.04

[linev]

Can you provide ROOT file?

Most probably, problem with decoding of data in JSROOT.

[sawenzel]

Thanks @linev ! I have sent you a link to example files per email.

[sawenzel]

I did some more experimentation also with the JSRoot plugin in Cernbox. The problem seems to be browser dependent. I find that it

a) doesn’t work on Chrome Version or Chromium (and hence VisualStudio Code which is probably chromium based) - neither on Mac nor on Ubuntu; Mac version is 113.0.5672.126 (Official Build) (arm64)

b) doesn’t work on Safari (Mac)

c) WORKS ok on Firefox 113.0.2 (Mac and Ubuntu)

[linev]

Problem is fixed by this commit:

Fix max stack limitation with Math.min.apply

It will appear soon in jsroot 7.3.2 release

[linev]

After 7.3.2 release also cernbox is now working properly

[linev]

See my reply in other thread:

Reading from http very slow

Probably I have an idea. cernbox does not accept Ranges in the requests and always return full file content. Even when it declares Accept-Ranges in the response headers. JSROOT has workaround - it request complete file content once and then reusing it. Of course, this does not work for large files. ROOT does not have such workaround and for each small request gets full content again and again. Therefore it may take very long time to process such file. Therefore I will not recommend to use …

Because of current cernbox limitations it is very inefficient to use it for large files.
As it is now, any ROOT file need to be completelty download by JSROOT before it can be used.

[Wile_E_Coyote]

Well, you write “any ROOT file need to be completelty download”, so it is not specific to CERNBox (i.e., using any server will behave the same way, or do I get it wrong).

[linev]

Yes, any server which does not accept or hide Ranges from http requests - will behave that way.
Therefore I put workaround in JSROOT - I saw such problem before several times.