Passing a string to Filter does not work

ROOT
1

I was just trying out the shiny new TDataFrame, when I ran into a problem.

The following code, which uses a lambda function to select events, works:

#include "TFile.h"
#include "ROOT/TDataFrame.hxx"
#include <iostream>
#include <stdlib.h>

auto tqCut         = [](double TrPChi2) { return TrPChi2 > 0.001; };

void reduce_df(std::string file)
{
   auto                           f = TFile::Open(file.c_str());
   ROOT::Experimental::TDataFrame df("DYTuple/DecayTree", f);
   auto selected = df.Filter(tqCut, {"muplus_TrPChi2"}).Filter(tqCut, {"muminus_TrPChi2"}).Count();
   std::cout << *selected << std::endl;
}

When trying to use a string isntead (as should be possible according to the documentation), using this code:

#include "TFile.h"
#include "ROOT/TDataFrame.hxx"
#include <iostream>
#include <stdlib.h>

void reduce_df(std::string file)
{
   auto                           f = TFile::Open(file.c_str());
   ROOT::Experimental::TDataFrame df("DYTuple/DecayTree", f);
   auto                           selected = df.Filter("muplus_TrPChi2 > 0.001 && muminus_TrPChi2 > 0.001").Count();
   std::cout << *selected << std::endl;
}

This does not even compile:

Processing reduce_df.cxx++("../ntuple/dy_tuple_12_md.root")...
Info in <TUnixSystem::ACLiC>: creating shared library /home/andreas/cernbox/work/drell-yan/scripts/./reduce_df_cxx.so
In file included from input_line_11:9:
In file included from ././reduce_df.cxx:2:
In file included from /cern/root-6.09.02/include/ROOT/TDataFrame.hxx:21:
In file included from /cern/root-6.09.02/include/ROOT/TDFOperations.hxx:14:
/cern/root-6.09.02/include/ROOT/TDFTraitsUtils.hxx:31:54: error: type 'const char *' cannot be used prior to '::' because it has no members
   using Args_t = typename TFunctionTraits<decltype(&T::operator())>::Args_t;
                                                     ^
/cern/root-6.09.02/include/ROOT/TDataFrame.hxx:421:52: note: in instantiation of template class 'ROOT::Internal::TDFTraitsUtils::TFunctionTraits<const char *>' requested here
      auto nArgs = ROOT::Internal::TDFTraitsUtils::TFunctionTraits<F>::Args_t::fgSize;
                                                   ^
././reduce_df.cxx:17:49: note: in instantiation of function template specialization
      'ROOT::Experimental::TDataFrameInterface<ROOT::Detail::TDataFrameImpl>::Filter<const char *>' requested here
   auto                           selected = df.Filter("muplus_TrPChi2 > 0.001 && muminus_TrPChi2 > 0.001").Count();
                                                ^
In file included from input_line_11:9:
In file included from ././reduce_df.cxx:2:
In file included from /cern/root-6.09.02/include/ROOT/TDataFrame.hxx:21:
In file included from /cern/root-6.09.02/include/ROOT/TDFOperations.hxx:14:
/cern/root-6.09.02/include/ROOT/TDFTraitsUtils.hxx:32:61: error: type 'const char *' cannot be used prior to '::' because it has no members
   using ArgsNoDecay_t = typename TFunctionTraits<decltype(&T::operator())>::ArgsNoDecay_t;
                                                            ^
/cern/root-6.09.02/include/ROOT/TDFTraitsUtils.hxx:33:53: error: type 'const char *' cannot be used prior to '::' because it has no members
   using Ret_t = typename TFunctionTraits<decltype(&T::operator())>::Ret_t;
                                                    ^
In file included from input_line_11:9:
In file included from ././reduce_df.cxx:2:
/cern/root-6.09.02/include/ROOT/TDataFrame.hxx:215:4: error: static_assert failed "filter functions must return a bool"
   static_assert(std::is_same<FilterRet_t, bool>::value, "filter functions must return a bool");
   ^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/cern/root-6.09.02/include/ROOT/TDataFrame.hxx:418:23: note: in instantiation of function template specialization 'ROOT::Internal::CheckFilter<const char *>' requested here
      ROOT::Internal::CheckFilter(f);
                      ^
././reduce_df.cxx:17:49: note: in instantiation of function template specialization
      'ROOT::Experimental::TDataFrameInterface<ROOT::Detail::TDataFrameImpl>::Filter<const char *>' requested here
   auto                           selected = df.Filter("muplus_TrPChi2 > 0.001 && muminus_TrPChi2 > 0.001").Count();
                                                ^
Error in <ACLiC>: Dictionary generation failed!

Is this behaviour just not finished yet, or am I doing something wrong?

Cheers,
Andreas

2

I am using ROOT 6.09.02, which already has this included as experimental feature.

3

Hi Andreas,

Jitted filters arrived immediately after that tag. I see two possible ways of solving this:

  1. move to master and have a taste of the bleeding edge
  2. wait a few days the release candidate tag which will include all goodies such as Snapshot of a dataframe on disk, cutflow statistics, jitted filters and new columns.

Unfortunately we do not checkpoint documentation for development releases and I pointed you to what has been generated from the master. I apologise for generating confusion here :frowning:

Cheers,
D

4

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