====== Comet, for existing Rocket users ======

===== Key Changes =====

For existing Rocket users, there are some major differences in how Comet operates and the features it has available - almost every aspect has been improved upon in some way, but there are some key items you need to know before you log on and start accessing the facility.

=== About the Facility ===

   * To access Comet you need to pass the [[https://hpc.researchcomputing.ncl.ac.uk/quiz/|HPC Driving Test]] before you can apply for an account
   * Comet has both [[:started:paying|Free to access]] and [[:started:paying|Premium/priority/paid]] resources
   * You must keep the [[:policies:access|information about your HPC project(s) updated and accurate]] in order to retain access to the facility; abandoned projects or those without regular updates (e.g. titles and descriptions) will be disabled and/or archived.
   * All aspects of your HPC project are managed [[https://hpc.researchcomputing.ncl.ac.uk/projects/|here on this website]] - that includes applying for a new project, maintaining descriptions and titles, project members, billing and job resource reports.

=== Slurm, Jobs & Partitions ===

   * The Slurm partition names have changed from [[:started:rocket_resources|Rocket]]. Please consult the new [[:started:comet_resources|Comet partitions]] and their intended uses.
   * You **must** now [[:started:first_job|include the account code]] of the project you are working in when submitting an sbatch or srun job.
   * Unlike Rocket, Comet supports [[:advanced:slurm_checkpoints|job checkpointing and resuming]].

=== Hardware ===

   * Low latency infiniband connectivity is **not** present on all node / partition types. If you want Infiniband connectivity, consult the [[:started:comet_resources|Comet partitions and resources]] page, or our [[https://hpc.researchcomputing.ncl.ac.uk/calc/resources/|detailed hardware specifications page]].
   * Comet has a **substantial** increase in GPU resources. Choose the hardware most relevant to your use case: [[https://hpc.researchcomputing.ncl.ac.uk/calc/show/2/9|GPU-S]] or [[https://hpc.researchcomputing.ncl.ac.uk/calc/show/2/10|GPU-L]]
   * All nodes of Comet use the same CPU model - dips and spikes in general CPU performance due to CPU differences should no longer impact your jobs
   * All nodes of Comet are **significantly** larger than Rocket: **256** CPU cores per node compared to just **44** of the standard nodes on Rocket. You may not need to scale your jobs over multiple nodes any longer.
   * The standard nodes of Comet have **significantly** larger memory than Rocket: **1.1TB** compared to just **128GB** of the standard nodes on Rocket. Consider this when scheduling your jobs.

=== Filesystems ===

   * There is **no** ''/nobackup/USERNAME'' directory - all data on Lustre should be kept in a [[:started:filesystems|group or project folder]] on ''/nobackup/proj/GROUPNAME''
   * NFS ''$HOME'' filesystem quotas are doubled compared to **Rocket**.

=== Software ===

   * We no longer use the [[:advanced:software:intel|Intel compilers or runtime libraries]]. Use either [[:advanced:software:gcc|GCC]] or [[:advanced:software:aocc|AOCC]] instead.
   * We no longer use the Intel MPI runtime. Use OpenMPI instead.

=== Containers ===

   * Singularity is **no longer supported**. Use [[:advanced:apptainer|Apptainer]] instead.
   * [[:advanced:apptainer|Apptainer]] containers can be created and run on login nodes without any special privileges.
   * [[:advanced:apptainer|Apptainer]] containers can be run on all compute node types.
   * [[:advanced:podman|Podman]] containers can be created and run on login nodes without any special privileges.
   * [[:advanced:podman|Podman]] containers can be run on all compute node types.

=== Interactive Applications / X11 ===

   * It is **no longer reccomended** to use X11 over SSH. Use [[:advanced:interactive|Open OnDemand]] to get a Linux desktop instead.
   * [[:advanced:rstudio|RStudio]] can be run as a graphical application in your browser via Open OnDemand
   * [[:advanced:jupyter|Jupyter Lab]] can be run as a graphical application in your browser via Open OnDemand
   * [[:advanced:matlab|Matlab]] can be run as a graphical application in your browser via Open OnDemand

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