Jean Zay: Modalities of regulating computing hours

A project obtaining hours on Jean Zay receives an initial hours allocation.

This initial allocation is automatically increased by a supplementary 25% of hours (by default) or increased to the number of hours proposed during the examination of the request for hours (if the difference between the number of hours proposed and the number of hours initially allocated is greater than 25%). The supplementary hours allocated (which are in addition to the initial allocation) can only be used if the target machine is under utilized; as soon as the hours consumption exceeds the initial allocation, the jobs have a lower priority.

Following the supplementary increase, you obtain an effective (or actual) allocation of hours on the Jean Zay machine

More precisely:

  • As soon as the consumption of a project exceeds its effective allocation of hours, the project will be blocked and none of the project members will be able to submit jobs.
  • A priority system based on a fairshare principle allows managing the execution of jobs on the machine in the most equitable way possible between the projects. This system takes into account various parameters including, in particular, the initial allocation of hours and the hours already consumed (the accounting decreases exponentially with time, with a half-life of 14 days).
  • A project which has under-consumed in the recent past (i.e. during the last days or weeks) benefits from a high priority for the execution of its jobs.
  • A project which has over-consumed in the recent past is not blocked. It can continue to submit jobs but they will have a lower priority; it can benefit from cycles which are available on the target machine because of low loads which otherwise would be lost.
  • To obtain information about the under- or over-consumption of your projects, you can launch the following command: 
    $ idr_compuse

This priority system maximizes the efficient use of machine cycles by:

  • Encouraging projects to use their hours regularly throughout the year in order to benefit from a high execution priority for a maximum number of hours.
  • In the event of under utilization of the machine, projects can either catch up on their lateness, or get ahead by benefiting from a lower execution priority with unlimited hours (except for the effective hours allocation).

Note that on the supercomputers installed at IDRIS prior to Jean Zay, a mechanism for recuperation of computing hours had been put in place: A project which had a large hours allocation but was under-consuming these hours, could lose hours. On Jean-Zay, this mechanism has been cancelled and replaced by the automatic regulation described above which enables having a homogeneous policy between the three national centres.

For any questions concerning the accounting of computing hours on Jean-Zay, please see this document.