# Output control¶

All the following parameters have sensible defaults and can be left out. The output prefix can be useful to control in which directory the output files end up. The final file name of all output files will be output_prefix + file name.

output:
prefix: lid_driven_cavity_flow
dolfin_log_level: warning
ocellaris_log_level: info

stdout_enabled

Log to standard out (console) in addition to the log file. Default on.

flush_interval

Flush the log and stdout at regular intervals (given in seconds). Defaults to 0. A value of a couple of seconds will not impact performance a lot and will make it easier to follow simulations running on clusters which typically buffers output for quite long befor you see anything

log_on_all_ranks

Write log files on all MPI ranks and not only on rank 0. This can be very helpfull when debugging a hanging simulation

stdout_on_all_ranks

Write to standard out on all ranks. This is not useful for large MPI runs, but can be somewhat useful for small single machine runs. Default off.

log_enabled

Write a log file. It is strongly recommended to leave this turned on, Many warnings can be written to the log and on the console they may scroll past too fast.

log_append_to_existing_file

If a log file is found, append to this, do not remove it and start with an empty file. Defaults to on so that restarts preserve the log.

show_memory_usage

This makes the log look ugly, but can help in discovering where memory is being allocated in case you want to trim some memory off your simulation. Default off.

hdf5_write_interval

Write restart file every N time steps (default 0, never write restart file)

hdf5_only_store_latest

Remove the previous restart file when the new one is finished writing to disk. Restart files can be large and you may only need the latest file.

save_restart_file_at_end

Defaults to on, write a restart file when the simulation ends

xdmf_write_interval

Write XDMF 3D plot files for Paraview and similar programs every N time steps. Defaults to 0, never write plot files. It is recommended to write XDMF to be able to visualize what is happening

xdmf_flush

Flush the XDMF file after each write so that it can be opened while the simulation is running.

vtk_write_interval

Write vtk files every N time steps. This writer is slow, but can handle some higher order fields (DG2) without interpolation to CG1 which is done in the XDMF writer currently. Not recommended unless you absolutely need this.

vtk_binary_format

Defaults to off, the binary writer currently has a bug so use the ASCII writer for now or fix the bug.

solution_properties

Compute and print properties such as divergence, courant number etc. This takes almost no time and is highly recommended

Co_lim

Stop the simulation if the Courant number exceeds this value, default 1000.

plot_mesh

Write the mesh to a separate plot file in the start of the simulation

plot_facet_regions

Write the mesh with each facet region in a different colour to a separate plot file in the start of the simulation. Useful for checking boundary conditions.

plot_bcs

Write the mesh with each boundary region in a different colour to a separate plot file in the start of the simulation. Useful for checking boundary conditions.

One boundary region can consist of multiple facet regions. Facet regions are also not needed at all, the inside_code can be used to specify boundary regions, see Boundary conditions.