How to Submit a Job

Job Submission

ClassAds

The Statistics Cluster is equipped with a powerful job queuing system called Condor. This framework provides efficient use of resources by matching user needs to the available resources by taking into account both the priorities for the hardware and the preferences of the job. Matching resource requests to resource offers is accomplished through the ClassAds mechanism. Each virtual machine publishes its parameters as a kind of classified advertisement to attract jobs. A job submitted to Condor for scheduling may list its requirements and preferences.

User Priority

When jobs are submitted, Condor must allocate available resources to the requesting users. It does so by using a value called userprio (user priority). The lower the value of userprio the higher the priority for that user. For example, a user with userprio 5 has a higher priority than a user with userprio 50. The share of available machines that a user should be allocated is continuously calculated by Condor and changes based on the resource use of the individual. If a user has more machines allocated than the userprio, then the value will worsen by increasing over time. If a user has less machines allocated than the userprio, then it will improve by decreasing over time. This is how Condor fairly distributes machine resources to users.

On the stats cluster, each student and faculty member are given a specific base userprio. Any non-UConn user of the cluster receives a different base value such that priority is given to UConn users. As users claim machines their user priority will adjust accordingly.

Submit File

Jobs are submitted with the condor_submit command with a job description file passed as an argument.

condor_submit myprog.condor

A simple description file goes as follows:

Executable = myprog
Requirements = ParallelSchedulingGroup == "stats group"
Universe  = vanilla

output    = myprog$(Process).out
error     = myprog$(Process).err
Log       = myprog.log

should_transfer_files = YES
when_to_transfer_output = ON_EXIT

Queue 50

Most of the variables are self-explanatory. The executable is a path to the program binary or executable script. The shown use of the requirements variable is important here to constrain job assignment to Statistics Cluster nodes only. All available nodes are tagged with ParallelSchedulingGroup variable in the ClassAds, so this is an effective way to direct execution to particular cluster segments. Physics and Geophysics nodes are also available but they are much older than the statistics nodes and may not contain all the necessary libraries. The output, error and log create the respective records for each job numbered by Condor with the $(Process) variable. A detailed example of a job is available here. If your job requires input from another file, the following can be added above the output line:

input = input.file

where input.file is the name of your file. It is also implied that the file is in the same directory as the submit file.

The universe option in the submission file specifies the condor runtime environment. Vanilla is the simplest runtime environment and executes a single-core program inside a single job slot. Multi-core and multi-processor jobs can be scheduled using the parallel universe. See the Condor documentation for more details on scheduling jobs in the parallel universe.

For optimal allocation of resources, serial jobs ought to be submitted to Condor as well. This is accomplished by omitting the number of job instances leaving only the directive Queue in the last line of the job description file outlined above. Obviously, $(Process) placeholder is no longer necessary since there will be no enumeration of output files.

Jobs Beyond the Statistics Cluster

To use the physics and geophysics cluster resources, it is important to set the Requirements carefully. Omitting (ParallelSchedulingGroup == "stats group") is insufficient because Condor presumes that the submitted executable can only run on the architecture from which the job is launched. This includes the distinction between x86 64 and 32 bit machines (the latter is still common on physics and geophysics cluster segments.) To insist that both architectures be used, include a requirement: (Arch == "INTEL" || Arch == "X86_64")