Out of memory using TEventList

ROOT
1

Dear Rooters,

I am working on some analysis for now few months using (basically) the same TSelector,
which recently crashed with the message:

Error: Symbol G__exception is not defined in current scope (tmpfile):1: Error: type G__exception not defined FILE:(tmpfile) LINE:1

Reading through the forum I concluded that this was coming from an out of memory,
especially when by adding #include into my header I had the message:

terminate called after throwing an instance of 'std::bad_alloc' what(): St9bad_alloc

I track down the piece of code responsible from this message and it turned out that it
was some TEventList (consistent with the fact that it is essentially the only change I made before the code crash)

I tried to create the TEvenlist(s) inside a TFile and write them regularly to disk. However
this did not change anything and I concluded that the TEventlist was kept in whole in memory (??).

Is there any way to ‘flush’ the TEventlist (like a TTree, without creating one) or compressing the list?

The bug started with ROOT version 5.15/08 and updating to 5.16 did not change anything

Thank you in advance for any help.
Julien

2

How many entries do you store in the TEventList?
TEventList entries are kept in memory.

Rene

3

Dear Rene,

This what the Print method outputs:

It is rather big …

Do you think that by embedding the TEventList into a TTree the problem may be
solved? Although I would rather not.

The data I am sorting come from many TTrees written in tens of files. Maybe having
a TEventList from each file will work? But then how I do that?

Regards
Julien

4

see class TEntryList announced in the 5.16 Release Notes at
root.cern.ch/root/Version516.news.html

A TEntryList is written for each file in a chain. When using a TChain
to process a list of files, the selected entry numbers are loaded when
loading a new file. Also the storage is more efficient than with the TEventList.

Rene

5

Dear Rene,

Thank you for the help.
I did not find any example yet on TEntrList and I just changing all my TEventList to TEntryList, within my TSelector. It seems Ok.
If I encounter problems I will post a new topic.

Julien