Root 6.04.14 hadd 100Gb and rootlogon

[msaimper]

Dear experts,

I am currently trying to use hadd to make an output file with a tree with size > 100 Gb.

I read:
https://root-forum.cern.ch/t/root-6-04-14-hadd-100gb-tfilemerger-recursiveremove/24117/4
and:

Hadd: 100Gb TTree Limit/compression levels

I want to merge 30 ~15Gb files containing an TNtuple using hadd, but get the following error: Fatal in <TFileMerger::RecursiveRemove>: Output file of the TFile Merger (targeting xxx.root) has been deleted (likely due to a TTree larger than 100Gb) Indeed, the target file is 100Gb when the error occurs. The files are generated from simulation data that writes an entry every break point. I have 512Gb of RAM on my server, and I don’t want to slow down hadd by using more compression if I can hel…

It seems that in my case the easiest solution is to create in the directory I execute “hadd” a rootlogon.C file with:
{
TTree::SetMaxTreeSize( 1000000000000LL ); // 1 TB
}

However, it seems that when I run “hadd” this new option is not taken into account. I tried two commands:

• hadd output.root input_*

• root -l
  root [0] TTree::GetMaxTreeSize()
  (Long64_t) 1000000000000
  root [1] gSystem->Exec(“hadd output.root input_*”);

I guess this is because hadd is not recompiled. Please could you tell me what the easiest way to take the new MaxTreeSize number into account in hadd?

I would prefer not to write a separate macro replicating the hadd behavior if possible.

Thanks for your help
Best wishes
Matthias

[pcanal]

Indeed hadd does not load the rootlogon file. However you can still manager using the following pattern.

Use a source file (let’s called it startup.C) like

#include "TTree.h"

int startup() {
  TTree::SetMaxTreeSize( 1000000000000LL ); // 1 TB
  return 0;
}

namespace {
  static int i = startup();
}

compile it into a shared library, for example with:

root.exe -b -l -q startup.C+

and then use LD_PRELOAD (DYLD_INSERT_LIBRARIES on MacOS) to preload that library:

 DYLD_INSERT_LIBRARIES=startup_C.so hadd  output.root input_*
 LD_PRELOAD=startup_C.so hadd  output.root input_*

Cheers,
Philippe.

[msaimper]

Dear Philippe,

thank you very much for your message, this is very helpful!

In addition, let me copy/paste here a little python script a colleague passed me which does the job also in case people visit this thread (*).

Thanks again for your help
Best wishes
Matthias

(*)

import ROOT
import os, sys

print 'Merging %s' % sys.argv[1]

print "Max tree size",ROOT.TTree.GetMaxTreeSize()
ROOT.TTree.SetMaxTreeSize(200000000000) # 200 Gb
print "Updated tree size",ROOT.TTree.GetMaxTreeSize()

rm = ROOT.TFileMerger(False)
rm.SetFastMethod(True)


path = 'mypath'
file_output = '%s.root' % sys.argv[1]
file_list = []
for path, dirs, files in os.walk(path):
  for filename in files:
    if ('%s_part' % sys.argv[1]) in filename: file_list.append(path+filename)

print "Input file list:",file_list
print "Output file:",file_output

for F in file_list:

    print "Adding ->",F
    rm.AddFile(F)

rm.OutputFile(file_output)
rm.Merge()