How to use FORtran from a ROOT macro

Conditions:To use the Fortran subroutines and functions 3 pre-conditions have to be met:

Fortran code has to be compiled with the Fortran compiler
It is provided by "cons" for all source files with the upper case "*.F" extension
To call any Fortran Subroutine / Function from C/C++ the Fortran subroutine C++ interface definition has to be provided
It has to be written "by hand"
To execute the the Fortran Subroutines /Functions the Fortran run-time environment may be needed at the run-time.
The Fortran Run-time libraries are provided by "root4star". They are not provided by the "plain" root.exe
(Optional) To be able to call the Fortran function from the Root C++ interpreter (from ROOT prompt) the RootCint dictionary for the C++/Fortran interface should be provided

The STAR "cons" automatically creates the RootCint dictionary for the all header files it discovery.

The examples follow:

Calling a FORtran subroutine from ROOT

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:

Create a directory mkdir StRoot/Fragmf
Add to that directory your fortran file with ".F" extension (upper case "F"), for example "fragmf.F"
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

> 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.