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Dos and Don'ts on Fox

Here is a collection of things to do and not to do on Fox.

• Always use the queue system for running jobs. The login nodes are only for file transfer, compilation, editing, job submission and short tests, etc. If you run production jobs on the login nodes, we will kill them and email you about it. If you continue to do it, we might have to lock your account.
• Do not run interactive calculations on the login nodes; use salloc or the interactive nodes.
• Do not use --exclusive in job scripts. It does not "play well" with --mem-per-cpu.
• We recommend you to be as precise as you can when specifying the wall time limit (--time) as it will inflict on how fast your jobs will start to run: It is easier for a short job to get started between two larger, higher priority jobs (so-called backfilling). On the other hand, if the job has not finished before the wall time limit, it will be cancelled, so too long is better than too short due to lost work!
• Similarly, try to be as precise as you can when specifying memory requirement. Just like with wall time, it can be easier to backfill a small job than a large one. On the other hand, if the job tries to use more memory than requested, it will fail, so too much is better than too little.
• Do not use --mem to specify memory requirement unless you also specify how many cpus are needed on each node (typically with --ntasks-per-node and optionally --cpus-per-task). We recommend using --mem-per-cpu (or --mem-per-gpu, if that applies) instead.
• Do not ask for more than one cpu, task or node unless your program can use more than one thread, process or node. Many programs are single-process, single-threaded, so will not be able to use more than one cpus on one node.

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