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What is a time allocation?

In order to run on PDC systems, users must belong to a time allocation (a CAC). The queuing system at PDC will use this information to set the priority of one user's job relative to other jobs submitted by other people. Time allocations can be personal or shared, but they always sets the maximum number of node-hours members of a time allocation are entitled to run jobs for on a computer every month.

Time allocations

Time allocations are sometimes referred to as CACs, which is an abbreviation of Charge Account Category. Using time allocations on every computer enables us two do two important things:

  1. Prioritize your submitted jobs compared to other people's jobs.
  2. Keep track of how much time that is used each month by different users and user groups.

Every user at PDC can belong to several time allocations - at least one for every computer/cluster that you submit jobs on.  Time allocations can be personal, or shared between several people. All time allocations (CACs) have at least the following properties:

  1. A CAC states the number of node hours members of that CAC are entitled to run jobs for every month.
  2. A CAC states which users belong to that CAC and are allowed to use the CAC's time for running jobs.
  3. Every CAC has an expiration date.
  4. A CAC is valid on a particular system/computer, although CACs with the same name can be present on several systems.

If a user does not belong to any time allocation when submitting a job then on most systems the job submission will fail.

Principal investigators

Since the test time allocation is so limited - both in time per month for running jobs, and in duration - many projects have applied for more time on a certain computer/cluster. For instance, a professor might apply for a time allocation that will cover the needs for all people in a certain research project.

The person that applied for the time allocation is called the  Principal Investigator, PI. All time allocations are now managed through SUPR, so users can be added or removed from the allocation directly using the SUPR web interface. The changes are then automatically applied overnight by various scripts.

Application forms

Depending on how much time you think that you need to run jobs and on which machines you want to run for there are different ways of applying for more time.

Time allocation sizes

Time allocations are divided into three categories depending on the amount of time.

  • Small time allocation if you need up to 5,000 core hours per month (only PhD students or higher)
  • Medium time allocation if you need between 5,000 - 200,000 core hours per month (only senior scientists)
  • Large time allocation if you need more than 200,000 core hours per month (only senior scientists)

The limit for medium allocations depends on the size of the machine. More information can be found at the SNIC website


SUPR allocations (Beskow and Tegner)

All allocations are handled on a national level through SNAC (Swedish National Allocations Committee), and the SUPR system. regardless of the size of the requested allocation.

Node hours and core hours

At PDC we allocate time on our systems in node hours. SNAC, allocates time in kilocore hours.

Node hours (n)  equal core hours (c) divided by the number of cores per node (cpn), i.e:

n = c/cpn

Conversely, core hours equal the number of cores per node times node hours:

c = cpn*n

The queuing systems at PDC uses node hours, and you are charged according to the number of node hours you have requested on a particular system.

Which time allocation do you belong to?

All systems

You can see what time allocations you belong to via the SUPR web page. Note that medium allocations normally have an extra m, at the start, e.g. SNIC 2015/1-1 is m.2015-1-1 on our system.


On systems which do not use EASY, you can see which time allocation you are a member of using the


command. Which will give you information on all the allocations you belong to and information on the recent usage of the allocation.

Acknowledge your SNAC/PDC time allocation

If you have written an article or a poster based on results achieved using computational resources given to you through a SNAC time allocation you might want to acknowledge this contribution. The SNAC committee will check your previous use of given time allocations if you in the future apply for more computation time.