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Reference Guide
mp103_processSelector.C File Reference

Detailed Description

View in nbviewer Open in SWAN Illustrate the usage of the multiproc TSelector interfaces with the h1 analysis example.

#include "TString.h"
#include "TROOT.h"
#include "TChain.h"
#include "TBranch.h"
#include "TH1F.h"
#include "TTreeReader.h"
const auto file0 = "http://root.cern.ch/files/h1/dstarmb.root";
const std::vector<std::string> files = {file0,
"http://root.cern.ch/files/h1/dstarp1a.root",
"http://root.cern.ch/files/h1/dstarp1b.root",
"http://root.cern.ch/files/h1/dstarp2.root"};
int mp103_processSelector()
{
// MacOSX may generate connection to WindowServer errors
gROOT->SetBatch(kTRUE);
TString selectorPath = gROOT->GetTutorialDir();
selectorPath += "/tree/h1analysis.C+";
std::cout << "selector used is: " << selectorPath << "\n";
auto sel = TSelector::GetSelector(selectorPath);
// The following code generates a crash when Davix is used for HTTP
// Davix does not seem fork-safe; the problem has been reported to the
// Davix developers. For the time being we disable this part.
// To repoduce the problem, uncomment the next line.
//
// #define __reproduce_davix
#if defined(__reproduce_davix)
auto fp = std::make_unique<TTree>(TFile::Open(file0));
auto tree = fp->Get<TTree>("h42");
#endif
TList *out = nullptr;
#if defined(__reproduce_davix)
// TTreeProcessorMP::Process with a single tree
out = pool.Process(*tree, *sel);
sel->GetOutputList()->Delete();
#endif
// TTreeProcessorMP::Process with single file name and tree name
// Note: we have less files than workers here
out = pool.Process(file0, *sel, "h42");
sel->GetOutputList()->Delete();
// Prepare datasets: vector of files, TFileCollection
TChain ch;
for (auto &&file : files) {
fc.Add(new TFileInfo(file.c_str()));
ch.Add(file.c_str());
}
// TTreeProcessorMP::Process with vector of files and tree name
// Note: we have more files than workers here (different behaviour)
out = pool.Process(files, *sel, "h42");
sel->GetOutputList()->Delete();
// TTreeProcessorMP::Process with TFileCollection, no tree name
out = pool.Process(fc, *sel);
sel->GetOutputList()->Delete();
// TTreeProcessorMP::Process with TChain, no tree name
out = pool.Process(ch, *sel);
sel->GetOutputList()->Delete();
return 0;
}
Authors
Anda Chelba, Gerardo Ganis

Definition in file mp103_processSelector.C.

TFileInfo
Definition: TFileInfo.h:39
kTRUE
const Bool_t kTRUE
Definition: RtypesCore.h:91
TH1F.h
fc
static struct mg_connection * fc(struct mg_context *ctx)
Definition: civetweb.c:3728
tree
Definition: tree.py:1
TSelector::GetSelector
static TSelector * GetSelector(const char *filename)
The code in filename is loaded (interpreted or compiled, see below), filename must contain a valid cl...
Definition: TSelector.cxx:142
TBranch.h
TChain::Add
virtual Int_t Add(TChain *chain)
Add all files referenced by the passed chain to this chain.
Definition: TChain.cxx:228
TTree
Definition: TTree.h:79
TTreeProcessorMP.hxx
TFile::Open
static TFile * Open(const char *name, Option_t *option="", const char *ftitle="", Int_t compress=ROOT::RCompressionSetting::EDefaults::kUseCompiledDefault, Int_t netopt=0)
Create / open a file.
Definition: TFile.cxx:3946
ROOT::TTreeProcessorMP
This class provides an interface to process a TTree dataset in parallel with multi-process technology...
Definition: TTreeProcessorMP.hxx:44
TString
Definition: TString.h:136
TString.h
TROOT.h
TChain.h
TTreeReader.h
TFileCollection.h
file
Definition: file.py:1
TObject::Delete
virtual void Delete(Option_t *option="")
Delete this object.
Definition: TObject.cxx:171
TChain
Definition: TChain.h:33
RMakeUnique.hxx
TList
Definition: TList.h:44
gROOT
#define gROOT
Definition: TROOT.h:406
TFileCollection
Definition: TFileCollection.h:39