Introduction to Hyak

Use Hyak when you need additional resources

  • More processing power
  • Models or data don’t fit in RAM

Think carefully about how to use Hyak

  • Do you really need to use it?
  • How can you use it efficiently?

Parallelization

  • Which steps are independent?
  • Which steps are bottlenecks?
  • How to minimize overhead?

Example: Simulation study

  1. Specify operating and estimation models
  2. Simulate 100 operating models
  3. Fit 300 estimation models
  4. Calculate metrics
  5. Summarize results

Example: Simulation study

  1. Specify operating and estimation models
  2. Simulate 100 operating models
  3. Fit 300 estimation models
  4. Calculate metrics
  5. Summarize results

Which steps are independent? Which step is the bottleneck? Are there steps that could be done together?

Example: Simulation study

Parallelization strategies

  • What step takes most time?
  • Which step is performed most often?
  • Are there natural save points?
  • Which computations can be reused?
  • Are there other limitations?

Checkpointing

  • Save progress
  • Restart from saved position
  • Use the ckpt queue

What is Hyak?

  • Mox
  • IKT

Logging in

ssh jkbest@mox.hyak.uw.edu

Keep your phone handy for 2FA!

How to choose a node type

Request an interactive node

  • build node:
srun -p build --mem=10G --time=1:00:00 --pty /bin/bash
  • stf-int node:
srun -p stf-int -A stf --cpus-per-task=28 --mem=120G\
    --time=1:00:00 --pty /bin/bash

Relevant SLURM arguments

srun
Request in interactive node
sbatch
Submit a batch job
-p
Partition; node type to use
-A
Account; usually stf
--cpus-per-task
Threads per program
--tasks-per-node
Processes to run on each node
--nodes
Number of nodes to request
--mem
Amount of RAM to request
--time
Time to reserve
--pty
Program to start

Connecting a second time

To see which node you are using:

squeue -u jkbest
  JOBID PARTITION ... NODELIST(REASON)
1838469     build ... n2232

From login node:

ssh n2232

Now monitor usage with e.g. htop

Modules

Key commands:

module --help
Reminders
module avail
List available modules
module apropos srchstr
Search modules for srchstr
module load abcdef
Attach module abcdef
module unload abcdef
Detach module abcdef

Using a build node

  1. Request a build node.
  2. Load the appropriate R module (or have your custom version accessible).
  3. Run R at the command line to open R.
  4. Use install.packages to install what you need.

Using an stf-int node

  1. Request an stf-int node (see above).
  2. Load the R module.
  3. Open R and run:

    library(TMB)
    
    runExample("simple")
    

Submit a batch job to stf

The “driver script” runs your analysis, including loading packages, reading data, and sourceing other files with functions etc. The SLURM script specifies the resources you need and how to run your driver script. Examples of scripts that I have used:

Note that these are just example scripts, I haven’t made them self-contained so they won’t run for you. That said, the fitsims.slurm file should be a good starting point for your own SLURM scripts. In the directory with the SLURM script, you can submit the job:

sbatch fitsims.slurm

Tips:

  • Write a single “driver” script
  • Use Rscript to run the driver script

There are three places to store files

Home

  • \home\xyz
  • Persistent, but low performance
  • Configuration files

GScratch

  • \gscratch\stf\xyz
  • Create your own directory.
  • 30-day limit
  • Scratch directory for computations

Lolo

  • Long-term tape storage
  • Must bundle files together

How to transfer files

sftp
Connect to mox.hyak.uw.edu
sshfs
Attach to local file system
git
Code managed in e.g. a GitHub repo

Advanced usage

  • Add module imports to your .bashrc file
  • Add other customizations
  • Set up sshfs
  • Compile your own R with MKL
  • Write your own module for everyone to use
Avatar
John K Best
PhD candidate

My research focuses on advancing the use of statistics in ecology and fisheries.