Re: updated geometry

["Mark M. Ito" <marki@jlab.org>]

Beni,

Thanks for getting that done. Sounds like real progress.

This brings up a code management issue that I have been wondering about 
for some time. It seems like we have a two step process: check-in new 
xml-based geometry information, then, by hand, generate the 
corresponding Fortran GEANT code, then check in the fortran code. This 
procedure violates the usual philosophy of only checking in "source" 
materials and allowing a make system to generate "derived" materials. It 
seems to have lead to some confusion about what we have in the Monte 
Carlo vs. what we have in the geometry. And I suspect some of the build 
problems I have had recently have to do with trying to maintain both 
"source" and "derived" in the Subversion repository.

My naive proposal is that we remove the Fortran GEANT code from the 
repository and regenerate it as part of the make system. Then one is 
guaranteed consistency between geometry specification and code. Also (if 
this can be done) a user can modify the geometry and use it immediately 
in the Monte Carlo without having to know the details of how to generate 
the Fortran code, i. e., play with a private version of the geometry 
without becoming an expert. Is there some fundamental problem with this? 
Too computationally expensive? Too many "helper" applications to 
install? Also, I have no idea how complicated it is to generate the 
Fortran code given you have everything you need installed.

On the subject of helper applications, I think we should be able to put 
together enough documentation and scripts to install them on most 
systems, especially if the applications are coming to us from 
experienced/professional programmers.

What do you and others think?

  -- Mark

Beni Zihlmann wrote:
> Dear colleagues,
> I updated the geometry in the repository. The geometry now reflects
> all the changes and design decisions that have been made lately.
> 1) remove outer most CDC layer thereby reducing the CDC radius by 1.6 cm
>    including the cable runs.
> 2) re-route the FDC cables to run upstream
> 3) add an 8mm aluminum plate on the inside of the BCAL
> 4) the BCAL readout segmentation is 4x6 (sector x layer)
>
> all these changes are now available the in geometry file hddsGeant3.F 
> located in
> src/programs/Simulation/HDGeant/
>
> cheers,
> Beni
>