[Solid_software] solid simulation job mem request

[Zhiwen Zhao]

Dear All

The bottom line is you need to have "MEMORY: 2000 MB" in your farm job 
script otherwise your gemc simulation job could be killed
The details are below

As indicated by Scicomp email on 7/27
Memory limits on farm jobs will be enforced using Linux Control Groups 
(cgroups). This change is being made to improve farm and Lustre 
stability by killing jobs that exceed their memory request. Jobs that 
are killed because of a memory constraint will show up in slurm as 
"JobState=OUT_OF_MEMORY Reason=OutOfMemory"

This means not only farm using physical mem instead of virtual mem, it 
enforce physical mem more strictly.
Your job can be killed if it's over limit

The default mem is only 512 MB.
gemc's mem use depends geometry and field map and is about 1GB.
evio2root can have about 1.5GB mem use.
So 2000 MB is a safe choice for now

One example of latest farm script is at
/work/halla//solid/sim/solid_gemc/SIDIS_He3_JLAB_VERSION_1.3/pass10/farm_solid_SIDIS_He3_moved_BeamOnTarget/

Let me know if you have any question.

Zhiwen