====== IDL on Physics linux systems ======

IDL is supported on the linux cluster primarily for specific research groups in Astronomy and Cosmology. A few licenses are also provided by Physics and Astronomy for general use.

To use IDL, you first need to load the software module:
  module load idl
  
After that, for a command line interface, type
  idl

or for IDL's development environment, type
  idlde

For interactive help, type
  idlhelp

===== The IDL Astronomy User's Library =====

<note>possibly outdated info?</note>

The IDL Astronomy Users Library is a central repository for low-level astronomy software written in the commercial language IDL. More info at http://idlastro.gsfc.nasa.gov/.

In order to use the network copy of this software, you must modify the IDL_PATH environment path.

For csh:
  setenv IDL_PATH "<IDL_DEFAULT>:/local/astro/idl_astro/pro"

for bash:
  export IDL_PATH="<IDL_DEFAULT>:/local/astro/idl_astro/pro"

===== Running multiple copies of IDL on the same machine =====

This hint was taken from Princeton Astronomy department: IDL hands out licenses based on hostname+username+display. If all three of those are equal, you can start as many sessions as you want and only consume one license. The modern habit of letting ssh create X tunnels causes the display name to be different for each ssh connection, even if several connections come from a single host. There are several ways of making your DISPLAY name the same for all such connections. The simplest is to note which your first one is (echo $DISPLAY), and set DISPLAY on other connections to that. Or for a console-only IDL session, simply unset DISPLAY completely.

===== Running IDL jobs without license restrictions =====

The IDL Virtual Machine which lets you run an IDL "executable" file without the need for licenses. Here's some more information about this feature from NYU Physics: http://www.physics.nyu.edu/grierlab/idl_html_help/distributing6.html

This can also help you run multiple IDL jobs in parallel through **condor** without being encumbered by available licenses. See http://www.iac.es/sieinvens/siepedia/pmwiki.php?n=HOWTOs.CondorAndIDLVirtualMachine for some pointers.

===== Problems and workarounds =====

none at present