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How to use the Fortran subroute from the ROOT macro

Submitted by fine on Mon, 2008-06-09 15:11. Under:

To use the fortran subroutine from ROOT C++ macro you are advised to use STAR build env as follows

Let's assume you need to call the subroutine:

  SUBROUTINE FRAGMF(IPART,X,Q2,XGLUE,XUQ,XDQ,XSQ,XUSEA,XDSEA,XSSEA,
&        XCHARM,XCHARMS,XBEAUTY,XBEAUTYS)
from C++ code (including ROOT macro).

You should:

  1. Create a directory mkdir StRoot/Fragmf
  2. Add to that directory your fortran file with ".F" extension (upper case "F"), for example "fragmf.F"
  3. Create there 2 C++ files: "Fragmf.cxx" "Fragmf.h"

where

Fragmf.h

: defines the C++ interface for your fortan code

#ifndef STAR_FRAGMF_H
#define STAR_FRAGMF_H
#include "TObject.h"
class Fragmf {
  public:
        void operator()
        (int IPART, double &X,    double &Q2,  double &XGLUE
                  , double &XUQ,  double &XDQ,  double &XSQ
                  , double &XUSEA,double &XDSEA,double &XSSEA
                  , double &XCHARM, double &XCHARMS, double &XBEAUTY
                  , double &XBEAUTYS) const;
  ClassDef(Fragmf,0)
};
#endif
Fragmf.cxx

: the implementation of your C++ code:

#include "Fragmf/Fragmf.h"

ClassImp(Fragmf)

extern "C" {
  // definition fo the FORTRAN sunbroutine interface
  void fragmf_(int *, double *X, double *Q2,    double *XGLUE
            , double *XUQ,      double *XDQ,    double *XSQ
            , double *XUSEA,    double *XDSEA,  double *XSSEA
            , double *XCHARM,  double *XCHARMS,double *XBEAUTY
            , double *XBEAUTYS);
}

void Fragmf::operator()
        (int IPART, double &X,    double &Q2,  double &XGLUE
                  , double &XUQ,  double &XDQ,  double &XSQ
                  , double &XUSEA,double &XDSEA,double &XSSEA
                  , double &XCHARM, double &XCHARMS, double &XBEAUTY
                  , double &XBEAUTYS) const
{
  // definition of the C++ wrapper to simplify the FORTRAN
  // subroutine invocation
  int i = IPART;
  fragmf_(&i, &X,    &Q2,    &XGLUE,  &XUQ
            , &XDQ,  &XSQ,    &XUSEA,  &XDSEA
            , &XSSEA,&XCHARM, &XCHARMS,&XBEAUTY,&XBEAUTYS);
}

3. You can add the ROOT C++ macro to test your inteface

StRoot/Fragmf/Fragmf.C

:

{
gSystem->Load("Fragmf");

int IPART =8;
double X,Q2,XGLUE, XUQ,  XDQ,  XSQ;
double XUSEA,XDSEA,XSSEA, XCHARM, XCHARMS, XBEAUTY;
double XBEAUTYS;
Fragmf fragmf;
// use "operator()" to proviide Fortran "Look and Feel"

fragmf(IPART,X,Q2,XGLUE, XUQ,  XDQ,  XSQ
      ,XUSEA,XDSEA,XSSEA, XCHARM, XCHARMS, XBEAUTY
      ,XBEAUTYS);
printf(" The values  from Fortran:\n"
" %f %f,%f, %f,  %f,  %f \n"
" %f,%f,%f, %f, %f, %f %f\n"
, X,Q2,XGLUE, XUQ,  XDQ,  XSQ
, XUSEA,XDSEA,XSSEA, XCHARM, XCHARMS, XBEAUTY
, XBEAUTYS);

}

Now, you are ready to create the shared library with "cons"

>  cons
and execute it with the ROOT
> root.exe -q StRoot/Fragmf/Fragmf.C
or
> root4star -q StRoot/Fragmf/Fragmf.C
One needs the very "root4star" as soon his / her Fortran code requires some Fortran Run-Time functions. For example it calls the Fortran I/O or PRINT statements.

In real life, you may not create a dedicated subdirectory StRoot/Fragmf you can add the 3 files in question to any existent STAR offline package.

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