Sim2Oogl - A Snap, Zeno and P File Conversion Programme

With this information, writing the programme was quite straightforward; invoked from the command line, the programme which is called sim2oogl requires the name of the data file to be converted, the format of the data file and the type of output desired.

• the format of the file : this refers to the structure of the file - it can be SNAP/Tipsy, Zeno or P.
  • Tipsy files are readable by the Tipsy data visualisation package; this allows results of N-Body simulations to be quickly displayed and analysed.
  • Zeno files are produced by Josh Barnes Zeno N-Body simulation package.
  • P files are simple ascii data files
• the type of output desired : this rather self evidently refers to the form of Geomview readable output that is produced by the programme. The user can choose one of:
  • position coordinates (X-Y-Z)
  • velocity coordinates (Vx-Vy-Vz)
  • position (X-Y) with line of sight velocity (Vz)
  • position (X-Y-Z) with velocity vectors (Vx-Vy-Vz)
  • all of the above

Additional options are available - the user can define the number of particles in the disks and halo as well the number of galaxies involved. The default assumes two galaxies without halos and each disk containing N/2 particles, where N is the total number of particles involved in the encounter.
Since Geomview is being used to display our data, I decided to further develop sim2oogl into an external module which can be used in tandem with the command line version of the programme. This module is called Sim2Oogl and it offers the user a GUI, built using the Tk/Tcl toolkit and scripting language, and invoked from within Geomview. The GUI extends the usability of sim2oogl, allowing the user to carry out a batch conversion of data files in addition to allowing files to be viewed once they have been converted.
The Tk GUI is built on top of the basic command line version of sim2oogl; the programme's function which handles input and output can be developed into a dynamically loadable extension that can be loaded into the Tcl interpreter using the load command. In principle, this is possible by working with Tk/Tcl's collection of C libraries, but a somewhat easier route was taken by using a programme called SWIG. SWIG requires an interface file in which the C functions to be used are declared as external objects; when invoked, SWIG then produces a wrapper file that is compiled and linked with the rest of the programme. In doing so, we get the dynamically loadable extension that can then be loaded into the Tcl script. Thus we have a means for exchanging information between the user interface and the basic conversion programme, as desired.
A comprehensive website Sim2Oogl1.0 in a Nutshell was prepared (and mirrored in the packaged documentation) for user support. Further modifications of the programme will be posted to this website as they come to fruition.