# Checkpointing

The following inputs must be preceded by “mfix.” and control checkpoint/restart.

| Description | Type | Default
--- | --- | --- | ---
restart | If present, then the name of file to restart from | String | None
check_int | Frequency of checkpoint output in timesteps number; if -1 then no checkpoints will be written | Int | -1
check_per_approx | Frequency of checkpoint output in simulation time; if 0 then no checkpoints will be written | Real | 0
check_walltime_interval | Frequency of checkpoint output in runtime (HH:MM:SS) | String | “”
check_file | Prefix to use for checkpoint output | String | chk
geom_chk_write | When True, writes the EB geometry data into geom_chk_file and additionally, geom_refined_chk_file, if levelset refinement is enabled. | bool | False
geom_chk_read | When True, reads the EB geometry data from geom_chk_file and additionally, geom_refined_chk_file, if levelset refinement is enabled. | bool | False
geom_chk_file | Name of the EB checkpoint file that is used to store or read the unrefined geometry. | String | geom_chk
geom_refined_chk_file | Name of the EB checkpoint file that is used to store or read the refined geometry, i.e. when levelset refinement is enabled. | String | geom_ refined_ chk