Commonly used phrases and terms
| Term | Explanation |
|---|---|
| 2-factor authentication | Authentication method using two factors for login. The first factor is typically a password; the second is a generated one-time code. |
| Batch job | A user-created script that defines what tasks should be performed. The script is submitted to a job scheduler to be executed on the cluster nodes. |
| Centre storage | Shared file system available on all nodes. LUNARC currently uses an IBM SpectrumScale parallel file system as its centre storage resource. |
| Compiler | Translates source code (C, C++, Fortran, etc.) into executables that can be run directly by the processor. |
| Core | Individual processing element — 48 per node on COSMOS. Also referred to as a CPU. |
| CPU | Central Processing Unit. A processor typically contains multiple CPUs (cores). |
| CPU-time | The sum of all execution times across all tasks in a parallel job. |
| Disk snapshot | LUNARC centre storage periodically saves snapshots of the file system. These can be used to recover files that have been accidentally deleted or modified. |
| GPU | NVIDIA or AMD co-processor, used for both compute workloads and graphics rendering. |
| Hardware accelerated graphics | Graphics rendering that uses a GPU hardware accelerator for drawing in 2D and 3D. |
| HPC | High Performance Computing |
| Job script | See Batch job. |
| Local disk | Disk storage local to each compute node. Not shared between nodes. Used as fast scratch space during jobs via $SNIC_TMP. |
| LUNARC | Lund University NIC Application Research Center |
| LUNARC HPC Desktop | Remote desktop solution provided by LUNARC, based on ThinLinc. |
| Module | A single software package in the module system, typically identified by a name/version pair (e.g. GROMACS/2023a). |
| Module system | System for managing software installations. Allows multiple versions of the same software to coexist. LUNARC uses Lmod. |
| MPI | Message Passing Interface — an API for writing multi-node parallel programs. OpenMPI and Intel MPI are the commonly available implementations on COSMOS. |
| NAISS_TMP | Environment variable used on some NAISS resources to point to the local scratch disk. Not used on COSMOS — use $SNIC_TMP instead. |
| Node | A physical computer/server in a compute cluster. |
| OpenGL | Open standard for hardware-accelerated graphics. |
| OpenMP | Open Multi-Processing — an API for shared-memory parallel programming within a single node using threads. |
| OTP | One Time Password — a short-lived code used as the second factor in two-factor authentication. |
| OTP-token | The code generated by the PhenixID OneTouch authenticator app for logging in to LUNARC systems. |
| Parallel job | A job consisting of multiple tasks running on one or more nodes simultaneously. |
| Partition | A group of nodes in a cluster that share common properties (processor type, memory, accelerators, etc.) and are scheduled together. |
| Processor | A multi-core processor housing multiple processing elements (cores/CPUs). COSMOS nodes have 2 processors per node. |
| PuTTY | Graphical SSH client for Windows. |
| Queue | When a job is submitted it enters a queue in the scheduler and waits until the requested resources become available. |
| Quota | The amount of disk space (and number of files) allocated to a user. Quota status can be checked with snicquota. |
| SLURM | Simple Linux Utility for Resource Management — the job scheduler used on COSMOS. |
| SNIC_TMP | Environment variable pointing to the local scratch disk on an allocated compute node on COSMOS. Fast I/O, deleted when the job ends. Use this in your job scripts. |
| Socket | The physical slot a processor plugs into — used as a synonym for processor. COSMOS nodes have 2 sockets. |
| SSH | Secure Shell — the encrypted protocol used to connect to LUNARC resources. Built into Linux and macOS; PuTTY provides it on Windows. |
| SUPR | NAISS User and Project Repository — the web portal for creating and managing project proposals for compute and storage resources. |
| SUPR Project | An approved project proposal in SUPR. |
| SUPR Proposal | A project proposal in SUPR that has not yet been submitted for approval. |
| Task | A software process — an instance of a running program with its own data and instruction stream. Can spawn multiple threads. Serial and pure MPI programs use one task per core. |
| Thread | A stream of instructions within a task. Threads within the same task share memory. Used by OpenMP and similar frameworks. |
| Toolchain | A matched set of compiler, MPI library, and supporting libraries used to build software consistently. |
| Walltime | The real-world elapsed time (wall-clock time) for which a job runs. |
Author: Jonas Lindemann (LUNARC)
Last Updated: 2022-10-06