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= HPC Workshop Spring 2026 =
= Module 8 of 8 - Job Checkpointing (Under construction) =
(content subject to change prior to the workshop)

== What is Job Checkpointing? ==
Job checkpointing is the process of ensuring or providing for the job's ability to resume processing - without repeating some or all of the processing already performed after termination due to either end of requested walltime or system outage. 

== Why is Job Checkpointing important? ==

* Checkpointed jobs can get started sooner out of the job queue pending state with a reduced requested run time. (See "backfill scheduling" in [https://slurm.schedmd.com/sched_config.html|SLURM Scheduling Configuration Guide].
* Most production clusters enforce strict walltime limits. (See see [wiki:cypress/about#SLURMresourcemanager SLURM (resource manager)].)
* A parallel MPI job can fail as soon as a single node in use crashes.
* Cloud-based job queues with high availability can enforce the use of pre-emptible job queues.

== Impacts of Job Checkpointing ==

* Job scripts require provision for requeuing after termination due to timing out or pre-emption.
* Applications without built-in checkpointing require additional programming effort.
* Runtime storing of complete program state at regular intervals requires additional time and I/O resources.
== Why use a HPC Cluster? ==
* '''tasks take too long'''
 * When the task to solve becomes heavy on computations, the operations are typically outsourced from the local laptop or desktop to elsewhere.  
 * Your computation may execute more efficiently if the code supports multithreading or multiprocessing. 
 
* '''one server is not enough'''
 * When a single computer can’t handle the required computation or analysis, the work is carried out on larger groups of servers.

== Job Checkpointing examples ==
* TBD