How to configure ROOT after installation

[Zman]

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ROOT Version: ROOTv6.12.06
Platform: Ubuntu 16.04

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As per this link, to run Pythia8 in ROOT6, I have to do the following:

Before compiling ROOT, configure ROOT by running the configure command including the following options

--enable-pythia8 
--with-pythia8-incdir=$PYTHIA8/include/Pythia8 
--with-pythia8-libdir=$PYTHIA8/lib 

In case ROOT has already been compiled before, it will only recompile the PYTHIA module and build the library libEGPythia8.

Now, my ROOT6 has been successfully installed. And running ./configure just gives:

ROOT is built with CMake, see Building ROOT from source - ROOT
Please run
mkdir obj; cd obj; cmake …; make -j 4

Please help and tell me how I can follow the afore mentioned instructions of that link.

[oshadura]

Hi,

Can I ask you which options (https://root.cern.ch/building-root) did you enable when you built ROOT? Did you enable pythia8?

[Zman]

Oksana shadura,

No, I unfortunately did not do that. But I now want to do that. Is it possible in anyway? Please tell.

[oshadura]

Hi,

Here is instructions how to build ROOT https://root.cern.ch/building-root - Section “Quick Start”.
Before installing ROOT you will need to install Pythia8.

Your CMake command will look something like this:

cmake ../ -Dpythia8=ON

If you have particular location with Pythia8 installation, then you will need to define next variables PYTHIA8_INCLUDE_DIR PYTHIA8_LIBRARY to avoid next situation below:

-- Could NOT find Pythia8 (missing: PYTHIA8_INCLUDE_DIR PYTHIA8_LIBRARY) 
-- Pythia8 not found. Switching off pythia8 option

[Zman]

oshadura,

I did it. And now the root-config --has-pythia8 gives ‘yes’. But still I can’t run the pythia8.C file in ROOT6. It shows the following error message:

root [1] .x pythia8.C
In file included from input_line_47:1:
/home/hp/ROOT/root/tutorials/pythia/pythia8.C:23:10: fatal error: 'Pythia8/Pythia.h' file not found
#include "Pythia8/Pythia.h"
         ^~~~~~~~~~~~~~~~~~
cling::DynamicLibraryManager::loadLibrary(): libpythia8.so: cannot open shared object file: No such file or directory
Error in <TInterpreter::TCling::AutoLoad>: failure loading library libEGPythia8.so for TPythia8.h
Error in <TInterpreter::AutoParse>: Error parsing payload code for class TGenerator with content:

#line 1 "libEG dictionary payload"

#ifndef G__VECTOR_HAS_CLASS_ITERATOR
  #define G__VECTOR_HAS_CLASS_ITERATOR 1
#endif

#define _BACKWARD_BACKWARD_WARNING_H
#include "TAttParticle.h"
#include "TDatabasePDG.h"
#include "TParticleClassPDG.h"
#include "TVirtualMCDecayer.h"
#include "TPrimary.h"
#include "TGenerator.h"
#include "TParticle.h"
#include "TDecayChannel.h"
#include "TParticlePDG.h"

#undef  _BACKWARD_BACKWARD_WARNING_H

In file included from input_line_47:1:
In file included from /home/hp/ROOT/root/tutorials/pythia/pythia8.C:24:
/home/hp/ROOT/root/include/TPythia8.h:69:10: fatal error: 'Pythia8/Pythia.h' file not found
#include "Pythia8/Pythia.h"
         ^~~~~~~~~~~~~~~~~~

Can you tell me what is wrong now? I have even enabled ‘share library’ option in pythia8 while installing.