Re: [ROOT] MC particles, TPythia6 ...cfortran.h

From: Rene Brun (Rene.Brun@cern.ch)
Date: Fri Jan 26 2001 - 08:58:30 MET


Hi Pasha,

Pasha Murat (630)840-8237 FNAL (630)859-3463 home wrote:
> 
> Dear ROOTers,
> 
> I think it would be quite helpful if TParticle in addition to 2 indices of
> mothers and 2 indices of daughters would also "remember" its own index in
> the original list of MC particles produced by event generator. I know that
> it is not strictly necessary, however whenever one is trying (and one
> is always doing it) to save just a small subset of the original list of
> particles, then in order to preserve a piece of original history each
> and every time he has to add this integer to TParticle in this or that way.
> 
>                         Any possible showstoppers?

You can use the TObject UniqueID.  myTParticle->SetUniqueID(index in list)

> 
> Few more observations:
> 
> - Pythia6 library in 3.0 doesn't compile - there seems to be a typo in TPythia6.h
>   (#include "TMCParticle.h" is typed in instead of #include "TMCParticle6.h")
> - after fixing this typo the library can't be loaded because of the unresolved
>    references.

You are correct. I fixed this problem.

> - describing FORTRAN common-blocks in C++  using cfortan.h (like it is done
>   in eg/inc/Hepevt.h) is not the best idea. cfortan.h  declares an external C++ GLOBAL,
>   corresponding to a FORTRAN common-block. In order to resolve this reference that at
>   linking stage linker picks up an ARBITRARY (the first one found!) FORTRAN
>   routine where this common block is described and links it in. In case
>   this first routine calls some other FORTRAN routines, one gets completely
>   unexplainable unresolved references resulting from a "cross-talk" between C++
>   and FORTRAN.  This is very similar to parasitic signal pick-up in
>   electronics.
> 

We had a simple solution with cfortran.h. If you find a more elegant,
safe and PORTABLE solution (Unix/Windows), I will include it.

Rene
>   Couple of years ago we at CDF waisted quit a bit of time to learn this.
> 
>                                                         best, Pasha



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