5. Interactive Services and Editing

Interactive Machines

Interactive services are provided via wren and newton. You cannot log in to fermat and green which are designated as batch only. If you wish to submit a job to fermat or green you should do so from wren. Job submissions to newton can be done by logging in to newton.

Users should note that the default limit on the number of processes on wren is set to 8. This can be increased, up to a maximum of 24, using the following command on the command line.

jlimit processes 16

You can put this command in your login file, but you must ensure you set it for wren only otherwise it will limit the processes that your batch jobs can use. For example for sh based shells:

if [ ${HOST} == wren ]
then
jlimit processes 24
fi

For csh based shells:

if ($HOST == wren )
then
jlimit processes 24
endif

Available editors

The main editors on both wren and newton are vi, which is part of unix, and emacs which is provided by the GNU Free Software Foundation. If you use emacs you should remember to set your DISPLAY environment variable to point to your workstation or PC. On wren you must load the sgi-freeware module to access emacs. Xedit is supported on all the machines.

Although you can edit files directly on wren and newton (consuming negligible CPU cycles), you may find it easier to edit files locally. To do this you will need to scp files from wren or newton to your local machine, perform the edits, then scp the files back again.

Version Control

If you are working on a complex code with other people, you may wish to consider using some form of version control. This allows just one person to edit a file at a time, records all the changes, and asks for a comment before saving the file and giving back access to other users. On both wren and newton the public domain CVS is available. RCS is available on newton. Note that both of these packages are unsupported and on wren you will need the sgi-freeware module loaded to access CVS. Please consult the relevant manual pages for more information.

Makefiles

To save unnecessary recompilation and to aid program development you should consider using a make file. This will contain inter-file dependencies, and running make will result in only modified sources files being compiled, before linking to make a final executable. For more information consult a standard unix reference book and man make.