Re: Hepevt.h

Nick van Eijndhoven (Nick@phys.uu.nl)
Thu, 13 Aug 1998 09:58:55 +0200

Pasha Murat wrote:
>
> Hi Rooters,
> an issue of interfacing to the existing FORTRAN packages (esp. MC
> generators) comes up again and again and I believe we need a policy on it.
> In particular, there is a (well-known to many of us) FORTRAN common-block
> /HEPEVT/ which gives kind of "standard" interface to MC event generators.
> However the one described in ROOT's Hepevt.h is dimensioned to 2000 whereas
> all (or almost all) the last versions of event generators have it
> dimensioned to 4000 - we move to higher energies...
> The definition in Hepevt.h is all right for Pythia 5.7,
> however it is inconsistent with HERWIG and Pythia 6.1. This inconsistency
> is fatal for the mixed-language code (at least on SGI/IRIX6).
> One of the possible solutions would be to change the dimensions
> of all the arrays in Hepevt.h to 4000, however in this case it will become
> incompatible (I'm afraid) the old (like Pythia 5.7) versions of the event
> generators.
> Another possibility would be not to distribute libEG by default, but
> to build it locally instead (with the proper dimensioned /HEPEVT/)
> There also could be other solutions and I believe that this issue
> deserves discussion.
>
> - Any opinions ? - regards, pasha.

Hi Pasha,
Here's my 2 pennies worth suggestion :

Introduce Hepevt2000.h and Hepevt4000.h to denote the 2000 and 4000 sized
arrays resp. In case one needs an increase once more (e.g. for the ALICE
events which are really big) one could just introduce e.g. Hepevt8000.h
without any further heavy modifications to the code.

Another possibility would be to drop old versions and take the new ones
(with the 4000 sizes) as the default ones.

Of course the BEST way is to get pure C++ versions of HERWIG, PYTHIA etc...
which for once and for all gets rid of the problem by using dynamic allocation. 

-- 


                                              Cheers,


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