//________________________________________________________________________________
TChain* CreateChain(const char *xmlfile, const char *type)
{
// Create a chain using url's from xml file
TString treename = type;
treename.ToLower();
treename += "Tree";
printf("***************************************\n");
printf(" Getting chain of trees %s\n", treename.Data());
printf("***************************************\n");
TGridCollection *coll = gGrid->OpenCollection(xmlfile);
if (!coll) {
::Error("CreateChain", "Cannot create an AliEn collection from %s", xmlfile);
return NULL;
}
TChain *chain = new TChain(treename);
coll->Reset();
while (coll->Next()) {
chain->Add(coll->GetTURL(""));
}
if (!chain->GetNtrees()) {
::Error("CreateChain", "No tree found from collection %s", xmlfile);
return NULL;
}
return chain;
}
void MergeCollectionFromGrid(const char * incollection = "test.xml", const char * outputfile= "dndeta_merged.root")
{
// for running with root only
gSystem->Load("libTree");
gSystem->Load("libGeom");
gSystem->Load("libVMC");
gSystem->Load("libSTEERBase");
gSystem->Load("libESD");
gSystem->Load("libAOD");
// load analysis framework
gSystem->Load("libANALYSIS");
gSystem->Load("libANALYSISalice");
// load dndeta task
gROOT->LoadMacro("AliAnalysisTaskdNdetaMC.cxx+");
TFileMerger * fileMerger = new TFileMerger(0); // dont merge local files
TGrid::Connect("alien://");
TGridCollection * coll = TAlienCollection::Open (incollection);
Int_t ifile=0;
while(coll->Next()){
fileMerger->AddFile(TString("alien://")+coll->GetLFN());
ifile++;
// if(ifile>2) break;
}
fileMerger->OutputFile("tmp.root");
fileMerger->Merge();
// Reopen the merged file, normalize histos and save them back.
// SOME DUPLICATED CODE... SOME CLEAN UP WOULD BE GOOD
AliAnalysisTaskdNdetaMC * localTask = new AliAnalysisTaskdNdetaMC("merger", "tmp.root");
localTask->Finalize();
TFile * fout = new TFile (outputfile, "recreate");
localTask->GetList()->Write();
fout->Close();
}