Frequently Asked Questions

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On this page you will find answers to some of most frequently asked questions about computing at Fine Hall.

E-mail

Read e-mail

You can read your e-mail in one of the following ways:

  • login via ssh to math.princeton.edu or pacm.princeton.edu and use pine, mutt or other terminal based E-mail clients
  • use Math Dept. WebMail
  • configure your e-mail client (like Thunderbird, Mozilla, Outlook and others) to access your e-mail via IMAP by following instructions in HowTos section about E-mail configuration

Forward e-mail from Princeton to your Math/PACM account

Open up in your browser OIT Account Management Page. You will be asked for your OIT username and password. Once logged in click on "Set Email Delivery" link on the left. That will bring "Where Is My Mail Going" information - if you you haven't changed your e-mail delivery location from default it is likely to be yourusername@mail.Princeton.EDU. Click on "Change Entry" button (found next to current delivery E-mail) and on next screen forward your Priceton email by setting your primary mail delivery location to your yourusername@math.princeton.edu E-mail address and then click on "Submit Changes".

Forward e-mail from your math account

To forward all of your math e-mail to another account, e.g. if you are leaving Princeton, create in your home directory .forward file that contains the e-mail address where your email will be forwarded. You can specify multiple E-mail addresses, each on its own line.

Vacation messages

Vacation messages can be set through Math/PACM webmail by going to https://www.math.princeton.edu/horde3/vacation/. You can also find vacation setting webpage under the "My Account" on the left side menu of the webmail.

At vacation webpage you can turn the vacation message on and off, specify the subject and content of vacation message replies and specify how often to send vacation message replies. Finally you can even set vacation start and end times.

Passwords

Types of passwords

Your Math/PACM account has two passwords associated with it - the Linux/LDAP password which is used for everything except accessing the fileserver through windows file sharing (also called smb, cifs of samba file sharing) and the windows/cifs password.

Password changing

If you need to change your password you should do it through the Math/PACM webmail interface. This way your LDAP password will be changed together with your windows/cifs password and therefore this will ensure they are the same. One logged in with your current password you will be prompted for your current and new password.

You can also find password changing webpage under the "My Account" on the left side menu of the webmail.

Running computations

Computation guidelines

These are the guidelines for running computations on Math/PACM machines:

  • Unless running computations on dedicated machines (like Comp or Macomp cluster or your own desktop) all jobs should be reniced to -19, e.g.:
nice -n 19 mycomputation

This will achieve that users of the machine you are using for your calculations are not impacted in their interactive use. Your job will still get all the available free CPU time.

  • Please make sure your computation does not consume too much memory. This is particularly important if you intend to run your computations on desktops used by others. Too much memory use on machines that do not have much to begin with will push the operating system into swapping which will severly impact both the user of the desktop and your own computation. Most Fine Hall desktops have only 512MB so you should make sure your job doesn't consume more than, say, 100MB or so - the less the better.
  • If your job requires a lot of memory and you do not have access to macomp cluster please feel free to run it on the login server - math.princeton.edu - which has both a pair of very fast processors and 4GB of memory. You should still limit your job to not more than 2GB of memory (or 3GB but only for a short period of time). Also take in account your per job memory consumption and the number of jobs you and others are running already on math.princeton.edu. E.g. running more than 1 computation that requires 2GB or more will quickly produce a non productive environment for all the users.
  • Computational jobs on math.princeton.edu are automatically reniced and you should limit yourself to at most 2 computations at any one time. If your computation is a long lasting one you do not have to renice your job but if you intend to run lots of short ones please do so (as automatic renicing does not kick in immediately).

Run computations and disconnect

If your computation is a long lasting one it is best if you start it up in such a way that you can logout and the computation will continue. This also prevents your computations from failing if your loose network connectivity. TO achieve this you should run your computations with nohup command. Nohup command will make sure the job is disconnected from the terminal, or in other words it will make sure that when you disconnect your job will not get the "I have loged out, please quit" signal. For example you should type something like this:

nohup nice -19 mycomputation_program > my_output.txt 2>&1 &

This will run your job, reniced to 19, and any output (both regular and error) will be placed into file my_output.txt. In other words If you want to place the error output into another file you can do:

nohup nice -19 mycomputation_program > my_output.txt 2> my_erroroutput.txt &

If you do not need the output from the command, e.g. because your program dumps its results directly into various files, you can redirect all of the other output into /dev/null:

nohup nice -19 mycomputation_program > /dev/null 2>&1 &

Run disconnected computations with matlab

If you want to run matlab computations you can do something like:

nohup nice -19 matlab -nodisplay -nodesktop -nojvm -nosplash < mymatlab_commands.m > my_output.txt 2>&1 &

Run disconnected computations with gp

For computations with gp (pari) just write your gp commands in a text file, say my_commands.gp, and then run the computation with something like

nohup nice -19 gp < my_commands.gp > my_output.txt 2>&1 &