====== Genga ======

Genga is an N-Body code designed to evolve systems with a dominant central mass (such as planetary systems or planetesimal disks). It tracks collisions, contains an analytical gas model, and supports a test particle mode. It runs on the GPU. The code, along with instructions, is available on [[https://bitbucket.org/sigrimm/genga|Bitbucket]].

Note that there is no hydrodynamics module. If you want to do disk hydrodynamics, you might want to look at [[Ramses]] or [[http://fargo.in2p3.fr/|Fargo]].

On the zBox, you need to compile and run Genga on the Tasna/Vesta nodes. See [[slurm|SLURM]] for instructions on how to launch batch and interactive jobs on Tasna/Vesta.

If you have trouble with the code itself, ask Simon. If you need help compiling, launching, or post-processing, you can also ask Volker.

===== Build Instructions =====

  * Log on to **malin1** or **malin2**
  * Create & navigate to some directory of your choice

<code>
$ mkdir -p /home/ics/username/src
$ cd /home/ics/username/src
</code>

  * Clone into the public repository

<code>
$ hg clone https://bitbucket.org/sigrimm/genga
</code>

  * Log in to a frontend node (f1, f2, f3, f4, f5, f6)
  * Depending on where you want to run Genga (Tasna or Vesta), allocate and launch an interactive job on one of the nodes

<code>
$ salloc --ntasks 1 --gres gpu:1 --partition vesta --account gpu <--- Vesta/K80X Cluster
$ salloc --ntasks 1 --gres gpu:1 --partition tasna --account gpu <--- Tasna/GTX580 Cluster
> salloc: Granted job allocation 3597976
$ srun --pty bash
</code>

  * Navigate to the source directory, and compile for the target architecture (Tasna/Vesta)

<code>
$ cd /home/ics/username/src/genga/source
$ make SM=37 <--- Vesta
$ make SM=20 <--- Tasna
</code>

  * Do a test run.

===== Random Stuff =====

  * The mysterious n1 and n2 parameters determine which particles are considered for close encounter groups. The parameter n1 is the scaling for the Hill radius, n2 the scaling for the relative velocity. **You shouldn't change these, unless you know what you are doing.**