Std::map of RNode in C++?

ROOT
1

Dear ROOT experts,

I am truly enjoying the use of RDataFrame and has been using it in my python scripts to make histograms and produce skimmed ntuples. In my workflow, I use dictionaries to map RNode(?) to strings. Here is a much simplified example of my script:

import ROOT
ROOT.gROOT.SetBatch()

df = ROOT.RDataFrame("mumu","ntuples.root")

df_filters  = {}
df_filters["passCut1"] =  df.Filter("passCut1")
df_filters["passSR"]   =  df_filters["passCut1"].Filter("passSR")
df_filters["passCR"]   =  df_filters["passCut1"].Filter("passCR")

print "passSR = " + str(df_filters["passSR"].Count().GetValue())
print "passCR = " + str(df_filters["passCR"].Count().GetValue())

What I’m trying to do right now is to make an equivalent C++ script by using std::map like the following:

#include "ROOT/RDataFrame.hxx"
#include "ROOT/RDF/RInterface.hxx"

using namespace ROOT;
using RNode = ROOT::RDF::RNode;
using namespace std;

void RDFMaps(){
  gROOT->SetBatch();    
  ROOT::RDataFrame df("mumu","ntuples.root");

  map<string, RNode> df_filters;
  df_filters["passCut1"] =  df.Filter("passCut1");
  df_filters["passSR"]   =  df_filters["passCut1"].Filter("passSR");
  df_filters["passCR"]   =  df_filters["passCut1"].Filter("passCR");

  cout << "passSR = " << *df_filters["passSR"].Count() << endl; 
  cout << "passCR = " << *df_filters["passCR"].Count() << endl;
}
int main(){
  RDFMaps();
}

When I try to compile the script and make an executable, I get the compilation errors below:

g++ -c -o RDFMaps.o RDFMaps.C -O3  -pthread -std=c++11 -m64 -I/cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include 
In file included from /usr/include/c++/4.8.2/functional:55:0,
                 from /usr/include/c++/4.8.2/bits/stl_algo.h:66,
                 from /usr/include/c++/4.8.2/algorithm:62,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TMathBase.h:33,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TString.h:26,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TNamed.h:26,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TDictionary.h:44,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TDataType.h:25,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TBuffer.h:24,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TDirectory.h:24,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TROOT.h:28,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/ROOT/RDataFrame.hxx:19,
                 from RDFMaps.C:1:
/usr/include/c++/4.8.2/tuple: In instantiation of 'std::pair<_T1, _T2>::pair(std::tuple<_Args1 ...>&, std::tuple<_Args2 ...>&, std::_Index_tuple<_Indexes1 ...>, std::_Index_tuple<_Indexes2 ...>) [with _Args1 = {std::basic_string<char, std::char_traits<char>, std::allocator<char> >&&}; long unsigned int ..._Indexes1 = {0ul}; _Args2 = {}; long unsigned int ..._Indexes2 = {}; _T1 = const std::basic_string<char>; _T2 = ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void>]':
/usr/include/c++/4.8.2/tuple:1079:63:   required from 'std::pair<_T1, _T2>::pair(std::piecewise_construct_t, std::tuple<_Args1 ...>, std::tuple<_Args2 ...>) [with _Args1 = {std::basic_string<char, std::char_traits<char>, std::allocator<char> >&&}; _Args2 = {}; _T1 = const std::basic_string<char>; _T2 = ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void>]'
/usr/include/c++/4.8.2/bits/stl_tree.h:140:49:   required from 'std::_Rb_tree_node<_Val>::_Rb_tree_node(_Args&& ...) [with _Args = {const std::piecewise_construct_t&, std::tuple<std::basic_string<char, std::char_traits<char>, std::allocator<char> >&&>, std::tuple<>}; _Val = std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> >]'
/usr/include/c++/4.8.2/ext/new_allocator.h:120:4:   required from 'void __gnu_cxx::new_allocator<_Tp>::construct(_Up*, _Args&& ...) [with _Up = std::_Rb_tree_node<std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> > >; _Args = {const std::piecewise_construct_t&, std::tuple<std::basic_string<char, std::char_traits<char>, std::allocator<char> >&&>, std::tuple<>}; _Tp = std::_Rb_tree_node<std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> > >]'
/usr/include/c++/4.8.2/bits/alloc_traits.h:254:4:   required from 'static typename std::enable_if<std::allocator_traits<_Alloc>::__construct_helper<_Tp, _Args>::value, void>::type std::allocator_traits<_Alloc>::_S_construct(_Alloc&, _Tp*, _Args&& ...) [with _Tp = std::_Rb_tree_node<std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> > >; _Args = {const std::piecewise_construct_t&, std::tuple<std::basic_string<char, std::char_traits<char>, std::allocator<char> >&&>, std::tuple<>}; _Alloc = std::allocator<std::_Rb_tree_node<std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> > > >; typename std::enable_if<std::allocator_traits<_Alloc>::__construct_helper<_Tp, _Args>::value, void>::type = void]'
/usr/include/c++/4.8.2/bits/alloc_traits.h:393:57:   required from 'static decltype (_S_construct(__a, __p, (forward<_Args>)(std::allocator_traits::construct::__args)...)) std::allocator_traits<_Alloc>::construct(_Alloc&, _Tp*, _Args&& ...) [with _Tp = std::_Rb_tree_node<std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> > >; _Args = {const std::piecewise_construct_t&, std::tuple<std::basic_string<char, std::char_traits<char>, std::allocator<char> >&&>, std::tuple<>}; _Alloc = std::allocator<std::_Rb_tree_node<std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> > > >; decltype (_S_construct(__a, __p, (forward<_Args>)(std::allocator_traits::construct::__args)...)) = <type error>]'
/usr/include/c++/4.8.2/bits/stl_tree.h:408:36:   required from 'std::_Rb_tree_node<_Val>* std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_create_node(_Args&& ...) [with _Args = {const std::piecewise_construct_t&, std::tuple<std::basic_string<char, std::char_traits<char>, std::allocator<char> >&&>, std::tuple<>}; _Key = std::basic_string<char>; _Val = std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> >; _KeyOfValue = std::_Select1st<std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> > >; _Compare = std::less<std::basic_string<char> >; _Alloc = std::allocator<std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> > >; std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_Link_type = std::_Rb_tree_node<std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> > >*]'
/usr/include/c++/4.8.2/bits/stl_tree.h:1669:64:   required from 'std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_emplace_hint_unique(std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::const_iterator, _Args&& ...) [with _Args = {const std::piecewise_construct_t&, std::tuple<std::basic_string<char, std::char_traits<char>, std::allocator<char> >&&>, std::tuple<>}; _Key = std::basic_string<char>; _Val = std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> >; _KeyOfValue = std::_Select1st<std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> > >; _Compare = std::less<std::basic_string<char> >; _Alloc = std::allocator<std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> > >; std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator = std::_Rb_tree_iterator<std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> > >; std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::const_iterator = std::_Rb_tree_const_iterator<std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> > >]'
/usr/include/c++/4.8.2/bits/stl_map.h:484:8:   required from 'std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](std::map<_Key, _Tp, _Compare, _Alloc>::key_type&&) [with _Key = std::basic_string<char>; _Tp = ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void>; _Compare = std::less<std::basic_string<char> >; _Alloc = std::allocator<std::pair<const std::basic_string<char>, ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void> > >; std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type = ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void>; std::map<_Key, _Tp, _Compare, _Alloc>::key_type = std::basic_string<char>]'
RDFMaps.C:20:24:   required from here
/usr/include/c++/4.8.2/tuple:1090:70: error: no matching function for call to 'ROOT::RDF::RInterface<ROOT::Detail::RDF::RNodeBase, void>::RInterface()'
         second(std::forward<_Args2>(std::get<_Indexes2>(__tuple2))...)
                                                                      ^
/usr/include/c++/4.8.2/tuple:1090:70: note: candidates are:
In file included from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/ROOT/RDataFrame.hxx:20:0,
                 from RDFMaps.C:1:
/cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/ROOT/RDF/RInterface.hxx:2481:4: note: ROOT::RDF::RInterface<T, V>::RInterface(const std::shared_ptr<_Tp1>&, ROOT::RDF::RInterface<T, V>::RLoopManager&, const ROOT::Internal::RDF::RBookedCustomColumns&, ROOT::RDF::RDataSource*) [with Proxied = ROOT::Detail::RDF::RNodeBase; DataSource = void; ROOT::RDF::RInterface<T, V>::RLoopManager = ROOT::Detail::RDF::RLoopManager]
    RInterface(const std::shared_ptr<Proxied> &proxied, RLoopManager &lm,
    ^
/cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/ROOT/RDF/RInterface.hxx:2481:4: note:   candidate expects 4 arguments, 0 provided
In file included from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/ROOT/RDataFrame.hxx:20:0,
                 from RDFMaps.C:1:
/cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/ROOT/RDF/RInterface.hxx:126:4: note: template<class T, typename std::enable_if<std::is_same<T, ROOT::Detail::RDF::RLoopManager>::value, int>::type <anonymous> > ROOT::RDF::RInterface<T, V>::RInterface(const std::shared_ptr<_Tp1>&)
    RInterface(const std::shared_ptr<Proxied> &proxied)
    ^
/cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/ROOT/RDF/RInterface.hxx:126:4: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8.2/functional:55:0,
                 from /usr/include/c++/4.8.2/bits/stl_algo.h:66,
                 from /usr/include/c++/4.8.2/algorithm:62,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TMathBase.h:33,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TString.h:26,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TNamed.h:26,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TDictionary.h:44,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TDataType.h:25,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TBuffer.h:24,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TDirectory.h:24,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/TROOT.h:28,
                 from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/ROOT/RDataFrame.hxx:19,
                 from RDFMaps.C:1:
/usr/include/c++/4.8.2/tuple:1090:70: note:   candidate expects 1 argument, 0 provided
         second(std::forward<_Args2>(std::get<_Indexes2>(__tuple2))...)
                                                                      ^
In file included from /cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/ROOT/RDataFrame.hxx:20:0,
                 from RDFMaps.C:1:
/cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/ROOT/RDF/RInterface.hxx:121:4: note: ROOT::RDF::RInterface<T, V>::RInterface(ROOT::RDF::RInterface<T, V>&&) [with Proxied = ROOT::Detail::RDF::RNodeBase; DataSource = void]
    RInterface(RInterface &&) = default;
    ^
/cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/ROOT/RDF/RInterface.hxx:121:4: note:   candidate expects 1 argument, 0 provided
/cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/ROOT/RDF/RInterface.hxx:117:4: note: ROOT::RDF::RInterface<T, V>::RInterface(const ROOT::RDF::RInterface<T, V>&) [with Proxied = ROOT::Detail::RDF::RNodeBase; DataSource = void]
    RInterface(const RInterface &) = default;
    ^
/cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/include/ROOT/RDF/RInterface.hxx:117:4: note:   candidate expects 1 argument, 0 provided
make: *** [RDFMaps.o] Error 1

Does this mean I can’t map RNode to strings in C++ using std::map or am I just not declaring the right type properly? Apologies for this question because I’m not familiar with the underlying machinery of RDataFrame.

Kind regards,
Fikri

=========================================================================
I am using ROOT version 6.18.00 on lxplus by sourcing the following file:

/cvmfs/sft.cern.ch/lcg/app/releases/ROOT/6.18.00/x86_64-centos7-gcc48-opt/bin/thisroot.sh
2

I don’t think you can create a std::map (i.e std::pair) with ROOT::RDF::RNode since it has not a default constructor.

Lorenzo

3

Hi,
indeed the absence of a default constructor for ROOT::RDF::RNode is what is causing your error.
In C++, this expression:

df_filters["passCut1"] =  df.Filter("passCut1");

needs to first default-construct the "passCut1" value in the map, and then copy-assign the right-hand side to it.

You might have better luck with something like this:

root [0] std::map<std::string, ROOT::RDF::RNode> m                                   
(std::map<std::string, ROOT::RDF::RNode> &) {}                                       
root [1] ROOT::RDataFrame df(10)
(ROOT::RDataFrame &) An empty data frame that will create 10 entries                 

root [2] m.insert({"head", ROOT::RDF::RNode(df)})

Hope this helps,
Enrico

4

Thank you for the explanation, @moneta, and your suggestion, @eguiraud. I was able to make it work the following way:

#include "ROOT/RDataFrame.hxx"
#include "ROOT/RDF/RInterface.hxx"

using namespace ROOT;
using RNode = ROOT::RDF::RNode;
using namespace std;

void RDFMaps(){
  gROOT->SetBatch();

  ROOT::RDataFrame df("mumu","ntuples.root");
  RNode rdf(df);

  map<string, RNode> df_filters;
  df_filters.insert({"passCut1",df.Filter("passCut1")});
  df_filters.insert({"passSR",  df_filters.at("passCut1").Filter("passSR")});
  df_filters.insert({"passCR",  df_filters.at("passCut1").Filter("passCR")});
  cout << "passSR = " << *df_filters.at("passSR").Count() << endl; 
  cout << "passCR = " << *df_filters.at("passCR").Count() << endl;
}

int main(){
  RDFMaps();
}

Cheers,
Fikri

5

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