Introduction: This workshop will introduce users to job management using the Slurm system - demonstrating how to create interactive jobs and submit jobs to the cluster queue that follow a basic workflow. After the workshop, participants will understand:

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01: Slurm

Topics:

• Slurm: 

  • Interactive sessions.

  • Job submission.

  • Resource selection.

  • Monitoring.

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1. Allocates access to appropriate computer nodes specific to your requests.

2. Framework for starting, executing, monitoring, and even canceling your jobs.

3. Queue management and job state notification.

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ARCC: Slurm: 

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Exercises:

• Slurm commands:

  • Start an interactive session: salloc

  • Submit a job: sbatch

  • Required parameters: account / time

  • Other parameters: 

  • Monitor jobs: 

    • squeue

    • sacct

    • sinfo

    • arccjobs

• Core hour usage: chu_user, chu_account

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• You submit a job to the queue and walk away.

• Monitor its progress/state using command-line and/or email notifications.

• Once complete, come back and analyze results.

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Submit Jobs: sbatch: Template:

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• How do I know what number of nodes, cores, memory etc to ask for my jobs?

  • Understand your software and application. 

    • Read the docs – look at the help for commands/options.

    • Can it run multiple threads - use multi cores (OpenMP) / nodes (MPI)?

    • Can it use a GPU? Nvidia cuda.

    • Are their suggestions on data and memory requirements?

• How do I find out whether a cluster/partition supports these resources?

• How do I find out whether these resources are available on the cluster?

  • Consult the wiki: Beartooth Hardware Summary Table

• How long will I have to wait in the queue before my job starts? 

  • How busy is the cluster? 

  • Current Cluster utilization: Commands sinfo / arccjobs and SouthPass status page.

• How do I monitor the progress of my job?

  • Slurm commands: squeue

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Common Issues:

• Not defining the account and time options.

• The account is the name of the project you are associated with. It is not your username.

• Requesting combinations of resources that can not be satisfied: Beartooth Hardware Summary Table

  • For example, you can not request 40 cores on a teton node (max of 32).

  • Requesting too much memory, or too many GPU devices with respect to a partition.

• My job is pending? Why? 

  • Because the resources are currently not available.

  • Have you unnecessarily defined a specific partition (restricted yourself) that is busy? 

  • We only have a small number of GPUs.

  • This is a shared resource - sometimes you just have to be patient…

  • Check current cluster utilization.

• Preemption: Users of an investment get priority on their hardware.

  • We have the non-investor partition.

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02: Workflows and Best Practices

Topics:

• What does a general workflow look like?

• Best practices in using HPC.

• How to be a good cluster citizen?

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Develop/Try/Test:

• Typically use an interactive session (salloc) where you’re typing/trying/testing.

• Are modules available? If not submit a New Software Request to get installed.

• Develop code/scripts.

• Understand how the command-line works – what commands/scripts to call with options.

• Understand if parallelization is available – can you optimize your code/application?

• Test against a subset of data. Something that runs quick – maybe a couple of minutes/hours.

• Do the results look correct?

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• Put it all together within a bash Slurm script: 

  • Request appropriate resources using #SBATCH

  • Request appropriate wall time – hours, days…

  • Load modules: module load …

  • Run scripts/command-line.

• Finally, submit your job to the cluster (sbatch) using a complete set of data.

  • Use: sbatch <script-name.sh>

  • Monitor job(s) progress.

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• Threads - multiple cpus/cores: Single node, single task, multiple cores.

  • Example: Chime

• OpenMP: Single task, multiple cores. Set environment variable.

  • an application programming interface (API) that supports multi-platform shared-memory multiprocessing programming in C, C++, and Fortran.

  • Example: ImageMagick

• MPI: Message Passing Interface: Multiple nodes, multiple tasks

  • OpenMPI: ARCC Wiki: OpenMPI and oneAPI Compiling, 

• Hybrid: MPI / OpenMP and/or threads.

  • Examples: DFTB and Quantum Espresso

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How can I be a good cluster citizen?

• Policies

• Don’t run intensive applications on the login nodes.

• Understand your software/application.

• Shared resource - multi-tenancy.

  • Other jobs running on the same node do not affect each other.

• Don’t ask for everything. Don’t use:

  • mem=0

  • exclusive tag.

  • Only ask for a GPU if you know it’ll be used.

• Use /lscratch for I/O intensive tasks rather than accessing /gscratch over the network. 

  • You will need to copy files back before the job ends.

• Track usage and job performance: seff <jobid>

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• Only accurate is the job is successful.

• If the job fails with say an OOM: Out-Of-Memory the details will be inaccurate.

• This is emailed out if you have Slurm email notifications turned on.

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03: Intermediate/Advance Next Steps

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Next Steps to look at: 

Future Workshops:

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• Introduction to Job Submission: 01: Nodes, Tasks and Processors

• Introduction to Job Submission: 02: Memory and GPUs

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Installing Software: 

Installing software comes in a number of forms:

• Download an existing binary that has built to run across the cluster’s operating system i.e. a Window’s executable will not run on a Linux based platform.

• Download source code:

  • Run using an interpret language - Python, R.

  • Configure and compile - C/C++/Fortran.

  • Are there specific scientific libraries you need to load? What dependencies does it have?

• Create a conda environment.

• Create and/or use an existing Singularity (docker) container image.

  • A container is a standard unit of software that packages up code and all its dependencies so the application runs quickly and reliably from one computing environment to another.

• Request via ARCC Portal: Request New/Updated HPC Software

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Conda: 

Conda:

• is a package, dependency and environment management for any language - Python, R, Ruby, Lua, Scala, Java, JavaScript, C/ C++, Fortran, and more.

• is an open source package management system and environment management system that runs on Windows, macOS and Linux. 

• quickly installs, runs and updates packages and their dependencies. 

• easily creates, saves, loads and switches between environments – which can be exported from one system and imported onto another - work on local desktop then setup on a cluster.

• can install and manage the thousand packages at repo.anaconda.com that are built, reviewed and maintained by Anaconda®.

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Getting Data On/Off the Cluster: 

• Data/File Transfer Tools

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04 Summary

Summary: 

Covered:

• Slurm: Interactive sessions, job submission, resource selection and monitoring.

• What does a general workflow look like?

• Best practices in using HPC.

• How to be a good cluster citizen?

• Intermediate/Advance next steps to consider looking at,.