redirectServers - Server not redirected

Rishabh_Mehta · January 24, 2026, 6:00pm

I have a pdf which is a convolution of an exponential with a resolution function (RooBDecay). I create an NLL from this and use it to fit. The fitting portion is fine, however, when I try to use this NLL for any other purposes (eg plotting or importing it to a workspace), I get hit with a redirectServers error which says that the resolution function could not be redirected:

[#0] ERROR:LinkStateMgmt – RooAbsArg::redirectServers(0x55fc1c8fd080,sc_pdf_btag): server res_core (0x55fc0921c4f0) not redirected

What could be done to resolve this? I am saving all my pdfs in a RooWorkspace and loading them if it helps.

Danilo · January 25, 2026, 7:14am

Hi,

Could you please provide a reproducer for the issue and share with us which version of ROOT you are using? We can then decide whether an issue on our tracker GitHub · Where software is built is in order.

Thanks!

Cheers,
D

Rishabh_Mehta · January 25, 2026, 9:17am

Hi!

I am attaching a MWE and an example dataset. This code fails in ROOT version 6.34.04 with the aforementioned error.

Thanks and regards,
Rishabh

mwe_data.root (14.0 KB)

mwe.py (3.4 KB)

Rishabh_Mehta · January 29, 2026, 9:02am

Hi!

This is a gentle reminder for this issue. Thanks!

jonas · January 29, 2026, 12:01pm

Thank you for reporting this problem!

I have fixed it now in ROOT:

github.com/root-project/root

[RF] Don't use `removeServer` to clean RooAbsAnaConvPdf compute graph

master ← guitargeek:abs_ana_conv_pdf

opened 11:53AM - 29 Jan 26 UTC

guitargeek

+0 -5

This follows up on 232a619f987f, where a unused server was removed when the RooA…bsAnaConvPdf is compiled for a given normalization set. Unfortunately, servers can't be meaningfully removed because it **always** results in a server-proxy-desync problem. If a server is removed, the corresponding `RooArgProxy` stays around as a data member of the RooAbsAnaConvPdf. When you then copy the RooAbsAnaConvPdf, the seemingly removed server is resurrected implicitly in the copy constructor of the the proxy, which leads to the confusing situation that a copy has a different server structure from the original. This will then confuse the server redirection when deep-cloning RooAbsArgs, manifesting in a problem reported on the forum, which is fixed by this commit: https://root-forum.cern.ch/t/redirectservers-server-not-redirected/64612/4 All other use of `RooAbsArg::removeServer()` outside the RooAbsArg destructor should also be reviewed to make sure that similar problems don't hide in other parts of the code. We should also consider deprecating that function from the public user interface, together with `RooAbsArg::replaceServer()`, which has the same problem.

I’ll also backport it to the ROOT 6.38 and 6.36 patch release branches, so you can benefit for this fix in the upcoming patch releases.

Cheers,
Jonas

Rishabh_Mehta · January 29, 2026, 7:28pm

Dear Jonas,

Thanks a lot for looking into this and providing a solution.