Regarding memory usage of TCahin Draw or RDataFrame Histo1D

[Chinmay]

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I have general question regarding RAM usage of different Actions of RDataFrame or TChain Draw.
I want to know when we call TChain::Draw or RDataFrame.Histo1D().GetValue(), once the function is executed and histogram is returned, what happens to buffers which are created to read relevant (for expression and cuts ) branches of the TChain ?
Are they cleared from memory ?
Also, in case of RDataFrame which is created using friend TTrees, who owns the TTrees passed to RDataFrame. Do we need to delete Friend TTrees or RDataFrame object will do it in its destructor.

[eguiraud]

Hi @Chinmay ,

@Chinmay

I want to know when we call TChain::Draw or RDataFrame.Histo1D().GetValue(), once the function is executed and histogram is returned, what happens to buffers which are created to read relevant (for expression and cuts ) branches of the TChain ?

They should be freed in both cases (@pcanal can correct me if I’m wrong).

@Chinmay

Also, in case of RDataFrame which is created using friend TTrees, who owns the TTrees passed to RDataFrame. Do we need to delete Friend TTrees or RDataFrame object will do it in its destructor.

In code such as:

TTree *t = GetTheTree();
t->AddFriend(GetTheFriend());
ROOT::RDataFrame df(*t);

the user owns the trees and is responsible for their deletion.

Cheers,
Enrico

[Chinmay]

Ok. Thank you.