Supercomputing FAQs

  1. How do I login to the DMC or SGI Ultraviolet?

  2. How do I change my password?

  3. I can't remember my password. How do I get a new one?

  4. I am on sabatical at another institution and cannot open a telnet session to the DMC or SGI Ultraviolet. What is wrong?

  5. How do I get information on commands related to "my_topic"?

  6. Where do I find documentation on using the DMC or SGI Ultraviolet?

  7. How do I find out what applications are available on the DMC and SGI Ultraviolet?

  8. What math and utility routines are available on the DMC and SGI Ultraviolet?

  9. How can I get help with my code?

  10. I compiled and ran my first big job on the computer, but after a few minutes it died with the message "Cpu limit exceeded". How do I run big jobs?

  11. What is the batch system and how is it used?

  12. How do I use X-window based software on the DMC and SGI Ultraviolet?

  13. How do I request new software for the DMC or SGI Ultraviolet?

  14. Is the supercomputer just for hard science and engineering?

  15. How do I get an account on the supercomputer?

  16. What do I do if my disk quota is exceeded?

  17. How do I find out how much memory and CPU time my job used?


1. How do I login to the DMC?

  1. "ssh" to dmc.asc.edu.

  2. Type your login ID at the "login:" prompt.

  3. Type your password at the "Password:" prompt.

  4. You should now see a Unix shell prompt " myname@dmc " (depending on which Unix shell you use).

How do I login to the SGI Ultraviolet?

  1. "ssh" to uv.asc.edu.

  2. Type your login ID at the "login:" prompt.

  3. Type your password at the "Password:" prompt.

  4. You should now see a Unix shell prompt " uv:~$ " (depending on which Unix shell you use).

2. How do I change my password?

  1. Type "passwd" at a prompt in your ssh session window.

  2. Type your old password at the "Old password:" prompt. Choose option 2 to enter a new password.

  3. Type your new password at the "New password:" prompt.

  4. Retype your new password at the "Re-enter new password:" prompt.

3. I can't remember my password. How do I get a new one?

  1. Contact the analyst at hpc@asc.edu.

  2. Call the AREN Helpdesk at (256) 971-7447 or (800) 338-8320.

4. I am on sabatical at another institution and cannot open a ssh session to the DMC or SGI Ultraviolet. What is wrong?

The Supercomputers are generally accessible from the Internet (excluding Europe and ASIA)

  1. First ssh to a machine at your home institution, then ssh to the DMC or SGI Ultraviolet.

  2. Contact the analyst at hpc@asc.edu.

  3. Call the AREN Helpdesk at (256) 971-7447 or (800) 338-8320.

5. How do I get information on commands related to "my_topic"?

  1. Type man -k at a shell prompt.

  2. Review list of commands generated by man -k to find those that seem appropriate.

  3. Type man for each command that you select.

  4. Third party software documentation is in /opt/asn/doc.

6. Where do I find documentation on using the DMC or SGI Ultraviolet?

  1. There is a pdf version of the user manual online at http://www.asc.edu/html/man.pdf

  2. Various applications may have online documentation in the directory /opt/asn/doc.

7. How do I find out what applications are available on the DMC or SGI Ultraviolet?

  1. Point your browser to http://www.asc.edu/supercomputing/software.html

  2. Contact David Young at (256) 971-7434 or dyoung@asc.edu.

8. What math and utility routines are available on the DMC and SGI Ultraviolet?

  1. IMSL Documentation is in the directory /opt/asn/doc/imsl.

  2. Public routines in FORTRAN and C can be found at http://www.netlib.org The slatec library is already installed on the DMC.

  3. The Intel Math Kernel Library is on the Ultraviolet.

  4. The SGI Ultraviolet SCSL library is on the Ultraviolet.

  5. The AMD core Math Library is on the DMC.

  6. The ATLAS library is on the DMC.

9. How can I get help with my code?

  1. Contact the analyst at hpc@asc.edu.
  2. Call the AREN Helpdesk at (256) 971-7447 or (800) 338-8320.

10. I compiled and ran my first big job on the computer, but after a few minutes it died with the message "Cpu limit exceeded". How do I run big jobs?

Interactive jobs are limited to 600 seconds.

  1. Information on how to run your job via the PBS job queueing system is in the user manual.

  2. Contact the analyst for help at hpc@asc.edu.

11. What is the batch system and how is it used?

Unlike PC's, these platforms are not designed for interactive work. Therefore, jobs that need running are submitted to a batch system for processing. The system handles multiple requests and schedules each job based on which batch queue was requested. To see a list of available queues, type nqslimits at the prompt.

  1. To utilize the batch system, contact the analyst for help at hpc@asc.edu.

  2. If you are using an application package, run scripts are available which automatically submit your job for you. These are usually located in /apps/scripts. All you do is run the script and answer the questions.

  3. If you are compiling your own code, the analyst had scripts designed to compile, execute and scp your code anywhere you desire.

  4. If you feel comfortable using Unix scripts, prepare a simple script that runs your executable and submit it to the appropriate queue with the run_script command as follows

    run_script <scriptname>

12. How do I use X-window based software on the DMC and SGI Ultraviolet?

The following commands can be used to setup a X-window connection to the DMC from a machine running UNIX X-windows. The commands might be slightly different from a Macintosh or PC with an X-window emulator.

  1. ssh -Y user_id@altix.asc.edu (where user_id is your login)

  2. Type the command.

13. How do I request new software for the DMC?

  1. Contact the analyst for assistance in preparing a request.

  2. In general, the more expensive the software, the greater your need will be to demonstrate interest in the software at multiple AREN client institutions.

14. Is the supercomputer just for hard science and engineering?

  1. No! Although chemists, engineers, and physicists currently dominate the use of the supercomputers, we also have biologists, musicians, environmental scientists, and other non-traditional users. With the growing interest in data-mining applications in a number of fields, we expect the diversity of our user community to increase.

  2. Please contact the HPC staff at (256) 971-7448 or hpc@asc.edu if you are contemplating non-traditional use of the DMC.

15.How do I get an account on the supercomputer?

There is an annual request for supercomputer accounts, via a web form. This is free for academic use in the state of Alabama, with commercial rates available. To get an account on the Ultraviolet, please go to:http://www.asc.edu/cgi-bin/account_request.cgi

After filling out the form, click "Submit Grant Application". This will generate a second page summarizing the information you entered. This second page must be printed, signed and faxed to (256) 971-7491. You will receive an email with your account password and information on accessing the SGI Ultraviolet within a couple days.

16.What do I do if my disk quota is exceeded?

All user accounts on the SGI Ultraviolet and DMC have disk quotas, which determine how much information can be stored in the home directory and it's subdirectories. By default, this quota is 1 GB. Users can see their disk quota by typing "quota" or "usage".

Please note that it has always been the policy that disk space on the supercomputers is for work in progress, not permanent backup or archival. Completed work should be transfered to a campus facility for permanent storage.

While a calculation is in progress, the /scratch file system provides a large amount of temporary disk space. The amount of space that can be used on /scratch is limited by the choice of job queue. To see the queue disk limits, type "qlimits". Any files created on /scratch must be removed within one week after the calculation completes. Files left on /scratch more than a week are automatically deleted.

If the nature of your work is such that you must have a larger home directory quota, you can request a larger quota. Users can request up to 20 GB quotas at no charge. Send an email with your request and a brief justification to David Young at dyoung@asc.edu

For quotas over 20 GB, please contact us to obtain a quote to purchase additional resources. To obtain a formal written quote for disk space, contact Mrs. Donna Daniel, Director of Client Services, at ddaniel@asc.edu or 334-242-0175.

17.How do I find out how much memory and CPU time my job used?

Look in the error log site. This site has a name that ends with the job number.