• Interface 1: equiv_class_enable scheduler attribute

• Visibility: Private
• Change Control: Unstable
• Permissions: Write: Manager Read: Everyone
• Details: Using this attribute admin can enable the equivalence class capability in the scheduler
  • Usage: boolean
• Default: Unset/Enabled
  
  

• Interface 2: equiv_class_exclude scheduler attribute

  • Visibility: Public
  • Change Control: Stable
  • Permissions: Write: Manager Read: Everyone
  • Details: Using this attribute admin can exclude certain resources from being considered when building the equivalence classes.  These resources are excluded from both the Resource_list and select resources.
    • Usage: comma separated list of resources
    • Example: equiv_class_exclude: walltime, software
  • Default: Unset

Equivalence classes are a way to group identical jobs together.  Once one job in a class can not run, the scheduler knows the rest of the jobs in that class can not run.  

How they work:

1. The scheduler sorts jobs into priority order.  This may include sorting algorithms such as the job_sort_formula or fairshare. 
2. The scheduler starts considering jobs in sorted order
3. If calendaring is enabled, the first N (backfill_depth=N) jobs that can not run will be added to the calendar.
4. After calendering has finished, equivalence classes come into play.  Any time a job can not run, the rest of the jobs in its class are not considered during the cycle.

There is a new qmgr scheduler object attribute named 'equiv_class_enable' which will switch between the old and new behavior of this feature.

Usage: qmgr> s sched equiv_class_enable: True

Once equivalence classes are enabled, the scheduler will create a set of jobs that are identical.  An equivalence class is made up of jobs that have the same euser, egroup, project, select, place, and Resource_List resources.  Any undesired resources can be excluded by listing them in the 'equiv_class_exclude' sched attribute.  Any resource listed is excluded from both the Resource_List resources and the select resources.

The external behavior of this feature is seen in the following way in the scheduler logs:

Old:

...;Job Id;Considering job to run
...;Job Id;<Reason job can not run>
...;Job Id;Considering job to run
...

i.e. each job gets its own "Considering job to run line"

Example:

04/15/2015 16:01:18;1234.mars;Considering job to run
04/15/2015 16:01:18;1234.mars;Insufficient amount of resource: ncpus
04/15/2015 16:01:18;1235.mars;Considering job to run

New:

...;Job Id;Considering job to run
...;Job Id;<Reason job can not run>
<same line for rest of equivalence class>

Example:

04/15/2015 16:01:18;1234.mars;Considering job to run
04/15/2015 16:01:18;1234.mars;Insufficient amount of resource: ncpus
04/15/2015 16:01:18;1235.mars;Insufficient amount of resource: ncpus
04/15/2015 16:01:18;1236.mars;Insufficient amount of resource: ncpus
04/15/2015 16:01:18;1237.mars;Insufficient amount of resource: ncpus