Puma Demo

Index

• What is HPC
• What is Puma
• Access HPC Systems
• Access Puma
• Access Software on Puma
• Run Scripts on Puma
• Demo

What is HPC

High-performance computing (HPC) is the use of software and hardware to process data and perform complex calculations at high speeds. Supercomputers are the product of this innovation.

What is Puma

Released in mid 2020, Puma is the newest supercomputer at the University of Arizona. The system is available to all researchers at no cost.

Access HPC Systems

You must:

• Make an account at https://account.arizona.edu/welcome
• Enrolled in Netid+ https://webauth.arizona.edu/netid-plus/

After you have been authorized by your sponsor group you may ssh into the University of Arizona's bastion host, a login node, via the command line.

$ ssh <netid>@hpc.arizona.edu

Fill in the necessary credentials to complete the login.

Access Puma

After successfully logging into bastion host simply type $ puma to access a Puma login node.

The purpose of a Puma login node is for users to perform housekeeping work, edit scripts, and submit their job requests for execution on one/some of the cluster’s compute nodes.

This is not where scripts are run. To learn more about executing scripts look here

To move files between your local machine and Puma I you can:

• Create a GitHub repository to push and pull files
• Move files from local-->HPC using $ scp -rp filenameordirectory NetId@filexfer.hpc.arizona.edu:subdirectory
• Move files from HPC-->local $ scp -rp NetId@filexfer.hpc.arizona.edu:filenameordirectory .

Now that your account is associated with a sponsor group, you are granted access to the resources of that group. Each group has a monthly allocation of 70000 standard CPU hours on Puma and when you run a job, the hours used are deducted from your group’s account. For example, if you run a job for one hour using 5 CPUs, 5 CPU hours will be charged.

You can view your sponsor groups used and remaining hours by using the command:

$ va

Access Software on Puma

To start, request an interactive session for one hour:

$ interactive

This command takes you from Puma's login node to a compute node. Each compute node comes with:

• AMD Zen2 96 core processors
• 512GB RAM
• 25Gb path to storage
• 25Gb path to other nodes for MPI
• 2TB internal NVME disk (largely available as /tmp)
• Qumulo all flash storage array for shared filesystems
• Two large memory nodes with 3TB memory and the same processors and memory as the other nodes
• Six nodes with four Nvidia V100S GPU's each

Get a look at the available built in modules:

$ module avail

You'll see which modules are loaded into your system indicated by the (L) to the right of the listed modules. More specifically you may view a list of all loaded modules using $ module list

Load a module:

$ module load <software/version>

If you choose not to specify the version, then the latest version of the defined software will usually be loaded.

To swap a version of a software with another version use:

$ module swap <currentSoftware/CurrentVersion> <newSoftware/newVersion>

Run Scripts on Puma

After creating and compiling your code, write a SLURM job script.

SLURM is a scheduler software that will reserve resources and run work on the cluster's compute nodes when space becomes available.

To run a slurm job a .slurm file must be created blueprinting how to run your code.

This .slurm file is separated into two parts, resource requests and job instructions.

The first portion of your script tells the system the resources you’d like to reserve. This includes the number of nodes/cores you need, the time it will take to run your job, the memory required, your group's name, the partition, and any special instructions. Other optional job specifications may also be set such as a job name or requesting email notifications. Each line with one of these requests will start with #SBATCH. If you’d like to comment out optional specifications that you don’t want, change these to ### SBATCH. You may also delete them.

The second section tells the system exactly how to do your work. These are all the commands (e.g. loading modules, changing directories, etc) that you would execute in your current environment to run your script successfully. SLURM, by default, inherits the working environment present at the time of job submission. This behavior may be modified with additional SLURM directives. [1]

Submit your SLURM job:

$ sbatch <your_SLURM_script>.slurm

The output of this command gives you the job ID.

With the job ID you can track the status of the job:

$ squeue --job <job_id>

A status of PD means the job is pending. R indicates the job is running. When the job is finished you will not see any information regarding the job.

SLURM provides the output file of the job in the format <job_name>-<job_id>.out or however you defined the output file in the line # SBATCH --output=<output_file_format> from your SLURM script. This output file will capture all standard out and standard error messages printed from the executables.

Demo

Now that we understand basic HPC and Puma operations let's do a quick demo calculating the Mandelbrot set.

First, access the University of Arizona's bastion login node:

$ ssh <netid>@hpc.arizona.edu

Once there is a connection open Puma:

$ puma

Clone this repository into the directory that best suits you:

$ git clone https://github.com/CompOpt4Apps/AthanPumaDemo.git

Open mandelbrot_openmp.slurm in an editor and change the line cd ~/demo/AthanPumaDemo by giving the absolute path to AthanPumaDemo on your machine cd <path>/AthanPumaDemo

Submit the SLURM job:

$ sbatch mandelbrot_openmp.slurm

You will see a .ppm file, the output of the SLURM job. This file gives us the Mandelbrot set. When opened with an application that accepts .ppm files such as GIMP, an image of the set will appear.

References

• Ref 1: University of Arizona's HPC Documentation Puma Quick Start