ReadingAODBranches ExampleCode

To read all the branches of an ATLAS AOD File

#include <TROOT.h>
#include <TRFIOFile.h>
#include <TFile.h>
#include <TString.h>
#include <TTreePerfStats.h>
#include <TTree.h>
TROOT canIUseSomeRootCommands("name","title");
int main(int argc, char *argv[]) {
//RFIO example
TFile *_file0 = TFile::Open("rfio://pool2.glite.ecdf.ed.ac.uk//gridstorage008/atlas/2009-11-14/AOD.065320._00159.pool.root.3.4504984.0", "READ"); 
//Local (or mounted) file: 
//TFile *_file0 = new TFile("/exports/work/physics_ifp_gridpp_pool/Test/AODClone.root.5371914.0", "READ"); 

TTree* T= (TTree*)_file0->Get("CollectionTree");
Long64_t nentries = T->GetEntries();
//  Int_t cachesize=100000000;
//  T->SetCacheSize(cachesize); 
//  if (cachesize > 0) {
//    T->SetCacheEntryRange(0,nentries); 
//      T->AddBranchToCache("*",kTRUE);
//  }
TTreePerfStats ps("ioperf",T);
cout << "Total Entries: " << nentries << endl;

for (Long64_t i=0; i<nentries ; i++){
   if (i%100 == 0 ){
     cout << "processed" << i << " entries" << endl; 
   }
     T->GetEntry(i);
}
ps.SaveAs("aodperStraightRFIO.root");
ps.Print();
}

Compile using the Makefile like that below.

ROOTCFLAGS    = $(shell root-config --cflags)
ROOTGLIBS     = $(shell root-config --glibs)
CXX           = g++
CXXFLAGS      = -g -Wall -fPIC
LD            = g++
LDFLAGS       = -g 
LDFLAGS       += -m32
CXXFLAGS      += $(ROOTCFLAGS)
NGLIBS         = $(ROOTGLIBS) 
NGLIBS        += -lTreePlayer
NGLIBS        += -lEG
NGLIBS        += -lRFIO
GLIBS          = $(filter-out -lNew, $(NGLIBS))
.SUFFIXES: .cc,.C
# ================================================
IOPerformer:  IOPerformer.o
# -------------------------
       $(LD) $(LDFLAGS)  -o IOPerformer IOPerformer.o aod/aod.so $(GLIBS)
.cc.o:
       $(CXX) $(CXXFLAGS) -c $<

gmake
./IOPerfomer 

Then you can view this file within Root and plot the access pattern

root aodperStraightRFIO.root
root [0] ioperf.Draw()  

Making the aod shared library to link above (within root)

TFile *f = TFile::Open("YourAODFile.root")
f->MakeProject("aod","*","new++");

Reordering a file (within Root)

gSystem->Load("IOPerformer/aod/aod.so");   
TFile *_file0 = new TFile("/scratch/wbhimji//AOD.065320._00159.pool.root.3.4504984.0", "READ");
TTree* T= (TTree*)_file0->Get("CollectionTree");
TFile *newfile = new TFile("AODClone.root","recreate");
TTree *newtree = T->CloneTree(-1,"SortBasketsByEntry");
newtree->Print();
newfile->Write();