README File for "dk2nu" package

Purpose: 

   This package's code was developed to consolidate the disparate
   formats of neutrino beam simulation "flux" files.  There is code to
   support the ROOT TTree format, assist in filling it in the beam
   simulations, and interface to GENIE.

   These "flux" files encapsulate more than just the flux of neutrinos
   but information about the hadron or muon decay the gave rise to
   that neutrino.  Using the particulars allowed one to re-evaluate
   the probability (and energy) of the neutrino ray passing through
   any arbitrary point.

   There were at the time of this writing (2012-11-06) at least 4
   variants [gnumi (geant3-based), g4numi, g4numi-minerva, flugg] with
   many similar elements but also different additions and formatting
   (both of element type and naming, mostly capitalization).

Subdirectories:

   tree     - the ROOT TTree dk2nu entries and the metadata entries
   genie    - interface to genie
   etc      - auxillary files (such a location text file)
   include  - 
   lib      -
   bin      -
   doc      - documentation
   scripts/  - 
     load_dk2nu.C - example script for loading libraries into ROOT
                    and making include/lib paths known to CINT/ACLiC
     examples     - code fragments for common use
     convert      - code to convert old ntuples to the new common format

Building and packaging:

   The code separates classes that interface to GENIE from the others
   to limit the dependencies.  The build expect a DK2NU environment
   variable to point to the top directory containing this file.

   At this time the build uses an standalone scheme that assumes the 
   necessary products (compiler, ROOT, GENIE, etc) have been setup ahead 
   of time.  The results should be package-able into a UPS setup.

   If ROOT is compiled 32-bit the system should detect that and use
   the -m32 flag automagically.  The build system assumes that g++
   is the correct compiler.  It should also link shared libraries
   appropriately on Linux and OS X.

Environment variables:

   DK2NU     - must point at top directory
   CXXFLAGS  - [optional]  (e.g. force -m32)
   LDFLAGS   - [optional]  (e.g. force -m32)

   GENIE     - std build build area if building genie interface
   LIBXML2INC - location of libxml2 include (necessary for genie interface)

Use in ROOT or GENIE:

   easy method:
      root $DK2NU/scripts/load_dk2nu.C\(true,true\)

   alternatively at the prompt use:
      .L $(DK2NU)/lib/libdk2nuTree.so
   or if export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:${DK2NU}/lib"
      gSystem->Load("libdk2nuTree");