# K4.1 Basic principles of Job Scheduling

This skill provides an overview of the scheduling of jobs on a supercomputer.
It covers generic and widely used concepts that serve the purpose to maximize the efficiency of a supercomputer.

Batch jobs submitted to a job queue define the workloads in batch systems.
A workload manager of a cluster system typically deals with:
  * Job Control to provide a user interface for submitting jobs to job queues, monitoring their state during processing (e.g. to check their estimated starting time), and intervening in their execution (e.g. to abort them manually)
  * Scheduling and Resource Management to select a waiting job for execution and to allocate nodes to the job meeting all its other demands for computing resources (memory, special processing elements like GPUs, etc.)
  * Accounting to record historical data about how many computing resources (e.g. computing time) have been consumed by a job

## Learning objectives
  * Comprehend the exclusive and shared usage model in HPC.
  * Differentiate batch and interactive job submission.
  * Comprehend the generic concepts and architecture of resource manager, scheduler, job and job script.
  * Explain environment variables as a means to communicate.
  * Comprehend accounting principles.
  * Explain the generic steps to run and monitor a single job.
  * Comprehend scheduling principles (first come first served, shortest job first, backfilling) to achieve objectives like minimizing the averaged elapsed program runtimes, and maximizing the utilization of the available HPC resources.

## Subskills