Chapter 16
Command-line Options

--force-output, -f
Force checkpoint files and final field files to be written, even when they exist, and disable the creation of any backup files.

--help
Displays help information about the available command-line options for the executable.

--solverinfo [key]=[value]
Override a solverinfo (or define a new one) specified in the XML file.

--parameter [key]=[value]
Override a parameter (or define a new one) specified in the XML file.

--verbose
Displays extra info.

--version
Displays software version, and source control information if applicable.

--io-format [format]
Determines the output format for writing Nektar++ field files that are used to store, for example, checkpoint and solution field files. The default for format is Xml, which is an XML-based format, which is written as one file per process. If Nektar++ is compiled with HDF5 support, then an alternative option is Hdf5, which will write one file for all processes and can be more efficient for very large-scale parallel jobs.

--no-exp-opt
This option will disable the optimisation of the expansion list ordering for collection type operations using the default definition of what is in the input mesh file.

--npx [int]
When using a fully-Fourier expansion, specifies the number of processes to use in the x-coordinate direction.

--npy [int]
When using a fully-Fourier expansion or 3D expansion with two Fourier directions, specifies the number of processes to use in the y-coordinate direction.

--npz [int]
When using Fourier expansions, specifies the number of processes to use in the z-coordinate direction.

--npt [int]
When using parallel-in-time integration (Parareal driver), specifies the number of chunks to use in the time direction.

--part-info
Prints detailed information about the generated partitioning, such as number of elements, number of local degrees of freedom and the number of boundary degrees of freedom.

--part-only [int]
Partition the mesh only into the specified number of partitions, write to file and exit. This can be used to pre-partition a very large mesh on a single high-memory node, prior to being executed on a multi-node cluster.

--write-opt-file
This option forces the run to write a new optimsiation file by calling the auto-tuning option. Otherwise this is only done if a .opt file does not exist.

--use-opt-file [file]
Use the file provided with deifntiion of the collection optimisation for this run. By default the CI system runs using this option.

--use-hdf5-node-comm
Partition the Hdf5-format mesh in parallel to avoid one single thread runs out of memory in serial partitioning.

--set-start-chknumber [int]
Set the starting number of the checkpoint file. This overwrites the checkpoint number in the file-type initial condition.

--set-start-time [float]
Set the starting time of the simulation. This overwrites the time in the file-type initial condition.

--use-metis
Forces the use of METIS for mesh partitioning. Requires the NEKTAR_USE_METIS option to be set.

--use-scotch
Forces the use of Scotch for mesh partitioning. If Nektar++ is compiled with METIS support, the default is to use METIS.