This article explains how to:

  • use the IDL software on JASMIN    
  • run these tools on the scientific analysis servers and LOTUS
  • make efficient use of the IDL licences
  • use the MIDL software on JASMIN - NOW DEPRECATED

What is IDL?

IDL stands for Interactive Data Language. It is a licensed data manipulation toolkit made available on JASMIN. 

Availability of IDL on JASMIN

IDL is available on all  scientific analysis servers and LOTUS.

To get started with  IDL, login on one of  scientific analysis servers and run the commands:

$ # First add the IDL module 
$ module load idl  

$ # Then you can run IDL at the command-line 
$ idl  

IDL Version 8.4 (linux x86_64 m64). (c) 2014, Exelis Visual Information Solutions, Inc. 
Installation number: 406672. 
Licensed for use by: Science & Technology Facilities Council 

IDL> print,1+4        

For help information about either installation you can type one of these help commands:

$ module help idl  
----------- Module Specific Help for 'idl/8.2' --------------------  	
           Adds IDL 8.2 to your environment variables,  

Making efficient use of IDL development licences

We have a large pool of run-time licences and a much more limited pool of development licences. In each case, these consist of floating licences shared between JASMIN/CEMS machines and LOTUS.

Users are welcome to run multiple instances of IDL code, but for that purpose please make use of the run-time licences by compiling your code using a single development session and then running the pre-compiled code using the  -rt flag. An example of this is shown in the next section (below).

Please try not to run more than one or two simultaneous IDL development sessions. However, for licence purposes, each unique combination of username, hostname, and  $DISPLAY variable counts as a single session. So for example, if you run idl (development mode) in one window, then suspend it (ctrl-Z) and start another development session in the same window, this still is only counted as one session by the licence server because the username, hostname, and $DISPLAY are all identical between the two processes. But if you "ssh" in on two different windows, probably the $DISPLAY will differ between the two windows (e.g. localhost:10 and localhost:11), so if you start idl development sessions in each window they will require separate licences.

To see what licences you and others are using, you can use the following sequence of commands: 

$ module add idl/8.2 
$ export,, 
$ lmstat -a

When interpreting the numbers, note that a single session is counted as 6 licences.

Using IDL on LOTUS (via the run-time Licences)

IDL run-time licences are available for use on the LOTUS cluster. In order to specify use of the run-time licences please follow the instructions here. You need to compile your IDL code in order to run in run-time mode.

Here is an example program that you might want to compile

The example program, "foo", depends on some other functions.

======== =======
 pro foo  
 print, doubleit(10) end 
===== ===== 
function doubleit, n   
return, two() * n 
======= ======== 
function two   
return, 2 

You must save a compiled version of the code:

1. Compile the program:

IDL> .compile foo    <=== compiles top-level routine only 
% Compiled module: FOO.

 2.Use resolve_all to compile routines it depends on:

IDL> resolve_all     <=== recursively search for and compile modules called 
% Compiled module: DOUBLEIT. 
% Compiled module: TWO.

3. Save all compiled routines to a file:

IDL> save, /routines, file='foo.sav'

To run the program, using a run-time licence only:

$ idl -rt=foo.sav 
IDL Version 8.4 (linux x86_64 m64). (c) 2014, Exelis Visual Information Solutions, Inc.
Installation number: 406502. 
Licensed for use by: Science & Technology Facilities

NOTE: Using  -vm= instead of -rt= opens the save file in the IDL virtual machine. No run-time licence is required, but a splash screen must be dismissed interactively, so it is not suitable for queues on the cluster.

To see what routines are present in the save file:

IDL> .reset_session     <=== removes any existing compiled modules  

IDL> help               <=== show compiled modules (and variables); there shouldn't be any 
% At $MAIN$           
Compiled Procedures:

Compiled Functions:  

IDL> restore,'foo.sav'   <=== load contents of save file  

IDL> help 
% At $MAIN$          
Compiled Procedures:
     $MAIN$  FOO                     <=== this was loaded from foo.sav  

Compiled Functions: 
     DOUBLEIT    TWO            <=== so were these

Passing arguments

You can also pass arguments in to your code as follows:

In your code, use function  command_line_args, for example:

argsarray = command_line_args(count = nparams)<br>

Call the code with -args flag:

idl -rt=foo.sav -args 10 20 30<br>

command_line_args returns a string array, so convert type as required, e.g. n = fix(argsarray[0]) 

Example usage of IDL Run-time Licences in a MIDL program [NOW DEPRECATED]

NOTE: The "midl" module is no longer supported on JASMIN, because the latest version was dated

To run  MIDL, run the commands:

$ # First add the MIDL module $ module load midl    

$ # Then you can run MIDL at the command-line   

$ midl -d   IDL Version 8.2 (linux x86_64 m64). 
(c) 2012, Exelis Visual Information Solutions, Inc.  
Installation number: 406672. 
Licensed for use by: Science & Technology Facilities Council     

A complete list of UKMO IDL routines can be found in $IU_LIB/README.  
For on-line help on an individual routine, use the man command.  Enter man,'man' for information about this command.  
Met Office Hadley Centre IDL software (c) Crown Copyright  
Licensed to NCAS and the Department of Meteorology  
% Compiled module: STRREPLACE.  
% Compiled module: DATATYPE.  
% Compiled module: BASENAME.  
% Compiled module: NICE_X_COLORS.  


NOTE:  The "-d" argument is required because MIDL only currently runs in 64-bit mode.

You will need to include  @idl_startup in your main program even though normally midl runs this for you. Here is an example that reads the file onerec.pp (a copy of which can be found at /apps/idl_tools/example_files/onerec.pp on JASMIN), and prints some header info:

======== ======= 
pro mytest 
z = ppa('onerec.pp') 
print, 'LBNPT:', z.lbnpt 

We compile it:

$ module add midl 
$ midl -d 
MIDL> .compile mytest 
MIDL> resolve_all, /continue_on_error 
MIDL> save, /routines, file='mytest.sav' 
MIDL> exit

Before running, you may also need to set the following environment variable so that you have access to shared libraries when not running the "midl" script directly:

export WAVE_SHARED_PATH=$MIDL_DIR/ukmo_idl/dlm/Linux64<br>

Then run it:

$ idl -rt=mytest.sav 
% PPALIST: File ./onerec.pp contains 1 fields 
LBNPT:          192<br>

Note, the  /continue_on_error is needed because the routines info and compare are missing. We suspect that these routines may be present in WAVE but missing in IDL. Most likely the calls are not executed in any case, particularly if your code completes successfully when run "normally" using a development licence. If you add the following dummy code to the end of then the /continue_on_error is not necessary:

pro info 

function compare 

Note that in order to make this work, we made a small local tweak to the MIDL installation on JASMIN. If you wish to copy this procedure using a MIDL deployment elsewhere (using MIDL version 20140411), you may need to do the same, or else  .compile will fail on routines that contain @idlstartup. Here is the patch.

--- ukmo_idl/lib/defpp.orig     2016-06-06 19:00:45.793486745 +0100 
+++ ukmo_idl/lib/defpp  2016-06-06 19:00:49.857537573 +0100 
@@ -153,7 +153,8 @@
  ;; LPJC Always force 256 colours on Linux  
  IF wave_max_colors NE 256 AND !version.os EQ 'Linux' THEN BEGIN $ 
        wave_max_colors=256 & $ 
-       PRINT,'WARNING - Ignoring $WAVE_MAX_COLORS and providing 256 cell colour tables' 
+       PRINT,'WARNING - Ignoring $WAVE_MAX_COLORS and providing 256 cell colour tables' & $ 
 defsysv, '!Max_colors', wave_max_colors    


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