[SOLVED] Memory issues with TTree

ROOT
1

Dear All,

I am trying to save to TFile two TTree objects, that get filled by a selection of events taken by another TFile, that changes during the execution.
When I declare and create the TTree I do:

TFile * outputFile = new ...
TTree * TreeS = new ...

but then there is a loop that eventually opens different other TFiles for reading the events and filling the tree. From time to time I try

TreeS->Write();

in order to avoid filling up the RAM.
I get the error

Error in <TFile::WriteTObject>: Directory /nfs/cuore1/data/CUORE/ContinuousData/run301530/QRaw_RDCF_301530_C_C2_p041.root is not writable

as if ROOT was trying to write the tree in the file it was supposed to read from. I tried also to put

BranchS->SetFile(pOutputFile);

before the TreeS->Write() command, but nothing changed.
Can someone help me out?

Many, many (and even more!) thanks in advance.
Guido

ROOT Version: Not Provided
Platform: Not Provided
Compiler: Not Provided

2

Try to add outputFile->cd(); before the “Write”.

3

Thanks! That actually solves the problem of the tree being written to the wrong file but I guess somehow ROOT does not flush the RAM after that because I get very soon to 9 GB of memory usage, which is my limit, and the process gets killed. I tried to debug with

TTree->Print()
gDirectory->ls("-d")
gDirectory->ls("-m")

but I can’t get to understand anything useful.
In other words, is there any way to force the flushing of the RAM space allocated for the TTree and/or setting a limit for it?
The output I get from the commands above is

0.29171 % completed.
******************************************************************************
*Tree    :TreeS     : Signal Tree                                            *
*Entries :     3022 : Total =       121055535 bytes  File  Size =   47691584 *
*        :          : Tree compression factor =   2.50                       *
******************************************************************************
*Br    0 :V         : V[10000]/F                                             *
*Entries :     3022 : Total  Size=  121073113 bytes  File Size  =   47681716 *
*Baskets :     1879 : Basket Size=    3200000 bytes  Compression=   2.50     *
*............................................................................*
******************************************************************************
*Tree    :TreeB     : Background Tree                                        *
*Entries :      993 : Total =        39812995 bytes  File  Size =   15977746 *
*        :          : Tree compression factor =   2.49                       *
******************************************************************************
*Br    0 :V         : V[10000]/F                                             *
*Entries :      993 : Total  Size=   39817445 bytes  File Size  =   15977370 *
*Baskets :      993 : Basket Size=      32000 bytes  Compression=   2.49     *
*............................................................................*
* * * * * * * * * * * *
gDirectory->ls( -d ) LIST OBJECTS ON DISK
TFile**		/nfs/cuore1/scratch/gfantini/neuralnet/TMVA/input/InputTMVA.root	
 TFile*		/nfs/cuore1/scratch/gfantini/neuralnet/TMVA/input/InputTMVA.root	
  KEY: TTree	TreeS;3	Signal Tree
  KEY: TTree	TreeS;2	Signal Tree
  KEY: TTree	TreeB;2	Background Tree
  KEY: TTree	TreeB;1	Background Tree
gDirectory->ls( -m ) LIST OBJECTS ON RAM
TFile**		/nfs/cuore1/scratch/gfantini/neuralnet/TMVA/input/InputTMVA.root	
 TFile*		/nfs/cuore1/scratch/gfantini/neuralnet/TMVA/input/InputTMVA.root	
  OBJ: TTree	TreeS	Signal Tree : 0 at: 0x2ae26e0
  OBJ: TTree	TreeB	Background Tree : 0 at: 0x2ae2a10
^C
4

After you “Write” both trees, try to add:

delete outputFile; // automatically deletes TreeS and TreeB, too

or use something like:

// ... fill TreeS ...
outputFile->cd();
TreeS->Write(); delete TreeS;
// ...
// ... fill TreeB ...
outputFile->cd();
TreeB->Write(); delete TreeB;
// ...
// ... we are done ...
delete outputFile;
5

Thanks a lot for the suggestions!
In the end I realized that the memory issue was coming from a bug I introduced that had nothing to do with ROOT (I just forgot to free a double *).
But the other part outputFile->cd() was really helpful. Thanks a lot for that.

6

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