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This page is not a comprehensive listing of the group's computing resources, but contains some useful starting points and links to other references.

UNIX Topics


UNIX services are currently provided through the Department and the University via the glue network. General access to these resources are available through the University machine and through the Department machine Large computational jobs should be run on the group's machine, which is a DEC Alpha workstation purchased through Prof. Misner's numerical relativity grant. Although Prof. Misner and his students have priority use of this machine, it is generally available to all members of the group.

Applying for an account

There are two paths for obtaining accounts. Members of the department (faculty, postdocs, and students) apply differently than visitors. The domain name for email sent to accounts created by either process is

Applying as a Department member

Members of the Physics Department are eligible for glue accounts. Please see the Department's registration instruction page for details on obtaining your glue account. Members of the GRT group who want access to wheeler and who already have glue accounts should email their request to David Fiske at

Members of the GRT group are also eligible for additional storage space in group space. The allocation of group space is currently managed by David Fiske. Contact him for concerns about your quota.

Applying as a visitor

Visitors to the group may request a sponsored account on the glue system. To do so,
  1. Telnet to Use the login register. Leave the password field blank.
  2. If you have a University ID (unlikely if you are a visitor), enter it when prompted. If you do not have an ID, you will have to invent one which is unique to the system and 9 digits in length.
  3. After completing the online registration, send an email to Ted Jacobson ( with your chosen user name and your ID number.

Visitor accounts have a fairly small home directory quota, but visitors will be given additional storage space in the GRT group space.

Renicing your jobs

If you are running long calculations on wheeler (or any machine for that matter), please be kind and renice your job. This tells the machine that it will be a long job and properly allocates the CPU time so that short jobs continue to be short.

In order to renice, you will need the process id number assigned to your job by the operating system. Typing

ps -fu <username>
at the command line will generate a listing of all of the processes that you are running on the machine together with each processes's id number. Once you have the process id number, type
renice -n 20 <procid>
at the command line.

When should you renice? For long jobs (a day or more) you should always renice.

Access to tools

Via our connection to the campus-wide glue network, we have access to a large number of standard computational tools. The Department's computing page lists many of these resources. Please refer to it first for questions. Do note, however, that some programs must be "tapped" before they can be accessed. In particular, this affects LaTeX, Maple, and Mathematica. They are made available, respectively, by the commands:
tap tetex
tap maple
tap mathematica

For those interested in software development, there are two C/C++ compilers available. The machine native compiler on wheeler is cc for C and c++ for C++. The GNU C/C++ compilers are available through the standard gcc. For Fortran, use F77 and F90. The GNU debugger gdb is available and working, while, as of this writing, ddd is technically available but not functional. To enable core dumps, you may need to type

limit core u
at the command line.

Group space

People doing a small amount of work on the UNIX system will probably be fine using their home directories for storing their files. (Except for visitors, who have very small home directories.) Your home directory is where you start each time that you log into the system and where you go if you type cd ~ at the command line.

People doing more work on the system will run out of space in the their home directories. They should then utilize the GRT group space. Each GRT user has group space in the directory

or can get such space by contacting David Fiske (

Linux Topics


At the moment there is one Linux box in the group dedicated to computational tasks (i.e. not someone's PC). The machine (LBTNL -- linux box to be named later) does not have a name at the moment, but can be accessed by ssh via its IP number. This machine is primarily being used by Bei-Lok Hu and his collaborators, but accounts on it are available to members of the group. Contact Chad Galley to setup an account.


MathTensor for Mathematica has been installed on this machine. In order to use the package, you must add the following lines to your Mathematica init file init.m:
$Path= Join[$Path,{"/usr/local/Wolfram/Mathematica/4.2/AddOns/Applications/MathTensor"}];
The init.m file is located in your home directory. (If you don't have such a file, created it with the above lines.)

Once you've appropriately modified your init file, you can start MathTensor from within a Mathematica session with the line

In[1] := <<MathTensor.m;

If you have additional questions, contact Nicholas Phillips.


For a general description of renicing as a concept and when to renice, see the UNIX renicing section of this document. The syntax on Red Hat linux machines is different than on the UNIX machines that we use here. To renice on Linux, issue the command
renice +20 <procid>
at the command line where <procid> is the process id number, which you can find by typing
ps -fu <username>
at the command line.

Personal Research Interest Pages

Everyone in the group should have a personal research interest page linked off of the group personnel page. In addition to this group webpage, which is standard to the group, you may also have a webpage through the glue system. The two are independent.

To create a new research interest page if you don't have one, contact David Fiske for help. To edit the information on your page, log onto a "glued" UNIX machine, and change to the

directory. There you will find a page with your name, which you can edit with any text editor (e.g. emacs or vi). If you find that you do not have the necessary permission to edit your page, contact David Fiske, who will correct the problem.

Links to Other Resources

If you cannot find what you need in this document, try these additional resources.
PNCE (Physics Network Computing Environment)
The Department's general information page
Project GLUE
The University-wide page for the GLUE system
AFS help at AEI-Potsdam
Help on the Andrew File System (AFS) from an external site
AFS help at DESY
Help on the Andrew File System from an external site

Last modified 16 November 2004 by T. Jacobson.