Command line invocation and flags

To run zCFD on the command line:

run_zcfd -c <case> [-n <ranks>] [-t <ranks_per_node>] [-o <threads>] [-d cpu|gpu]

Flag	Default	Meaning
`-c`, `--case`	required	the control file, `<case>.py`; the `.py` extension may be left out
`-n`, `--ntask`	1	the number of MPI ranks, and so the number of mesh partitions
`-t`, `--tpn`	1	the number of MPI ranks on each node
`-o`, `--otpt`	set by zCFD	the number of OpenMP threads for each rank, exported as `OMP_NUM_THREADS`
`-d`, `--device`	detected for each rank	`cpu` or `gpu`
`-v`, `--version`		print the zCFD version and exit
`-h`, `--help`		print the usage and exit

zcfd is a shorter name for the same command and takes the same flags.

The control file names each mesh with the mesh key of its entry under model. See Running zCFD for worked examples of these flags, and Running zCFD § Multiple Meshes and Overset Cases for a case with more than one mesh, which is run with the same command.

Licence check

run_zcfd --check-license

checks out the zCFD licence, reports each licensed product with its seats, expiry and source, and exits. It takes no case. See Installation and licensing.

Input Validation

zCFD provides an input validation script which can be used to check the solver control dictionary before run time reducing the likelihood of a job spending a long time queuing only to fail at start up.

The script can be executed from the zCFD environment as follows:

validate_input <case>

The script checks the control file against the schema. It does not read the mesh.

Batch Queue Submission

To run zCFD on a compute cluster with a queuing system (such as Slurm), the command-line environment activation is included within the submission script:

Example Slurm submission script "run_zcfd.sub":

#!/bin/bash
#SBATCH -J zcfd
#SBATCH --output zcfd.out
#SBATCH --nodes 2
#SBATCH --ntasks 4
#SBATCH --exclusive
#SBATCH --time=10:00:00
#SBATCH --gres=gpu:2
#SBATCH --cpus-per-task=16
source /INSTALL_LOCATION/zCFD-version/bin/activate
run_zcfd -n 4 -t 2 -d gpu -c <case>

This system has 2 nodes, each with 2 GPUs. One task is allocated per GPU, giving a total of 4 tasks. The value given to -n, in this case 4, on the last line should match Slurm 'ntasks' on line 5, and -t gives the 2 tasks on each node. The case is run in 'exclusive' mode which means that zCFD has uncontested use of the devices. Each node has a 64-core CPU, giving 16 CPU cores for each of the 4 tasks. The 'gres' line tells Slurm that there are 2 GPUs available on each node.

The submission script would be submitted from the command-line:

sbatch run_zcfd.sub

The job can then be managed using the standard Slurm commands.