============================================================================

     hamc  =  Hall  A  Monte  Carlo

     R. Michaels,  initial version Jan 2009; updated May 2018

============================================================================

This is a single-arm Monte Carlo used by the parity experiments
in Hall A.  It was used by HAPPEX-III, PVDIS, PREX, and C-REX.

Some documentation about hamc is here:
http://hallaweb.jlab.org/parity/prex/hamc

For version control, I'm using github:  
https://github.com/rwmichaels/hamc

A good way to proceed is to make your repository on github.com,
then Fork my repository, then "git clone" it to your local PC.
If you have useful changes you can make a "pull request" to me.

To proceed do the following

Compile:

    make clean
    make

Run

    ./prex    
or 
    ./happex
   (and don't forget the dot "." and slash "/")


Optional argument is the number of events, like this:

    ./prex 1000000

Histogram output

    hamc.root

To show some results, 

   root hamc.root
   root [7] .x ./macros/show4.C
   (etc)

I/O control of code

    prex.dat   to control prex
    happex.dat to control happex

You can find versions of prex*.dat in ./PREX directory.  You 
likely want "prex_hrstrans.dat" so copy that to prex.dat in the
run directory.  ("cp ./PREX/prex_hrstrans.dat prex.dat")

New in 2018 is the transport code THRSTrans.  The old fortran
code (LeRose functions) still exist but can be effectively turned
off by disabling the USEFORTRAN flag in the Makefile.  

For THRSTrans you need the separately maintained library.  
You can see from the Makefile where this located

  grep HRSTRANS Makefile 
  HRSTRANSLIB   = /home/rom/hrstrans1/lib
  ALL_LIBS = $(LIBS) $(HRSTRANSLIB)/libhrstrans.so
  INCLUDES += -I$(HRSTRANSLIB)

and you'll need to control HRSTRANSLIB.  Both libhrstrans.so
and the header THRSTrans.h need to be in this directory.
To obtain THRSTrans, you could use my git repo for that,
though in principle Seamus Riordan should be maintaining it.
https://github.com/rwmichaels/hrstrans

July 2021 : added HrsTrkCorr option (usetrkcorr in prex.dat).
But this is a specialist item, it's safest to leave that flag
out of the hrs_setup line in prex.dat control file.