# Checkpointing

The following inputs must be preceded by the prefix `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 number of timesteps; 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 | None
check_file | Prefix to use for checkpoint output | String | chk
geom_chk_write | When enabled, write the EB geometry data into `geom_chk_file` and additionally, `geom_levelset_chk_file` if levelset refinement is enabled. | Bool | false
geom_chk_read | When true, read the EB geometry data from `geom_chk_file` and additionally, `geom_levelset_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_levelset_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_ levelset_ chk