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# CHECKPOINT¶

Defines checkpointing options for restart capability.

## Required Cards:¶

CHECKPOINT
Opens the CHECKPOINT block, although block form is not required if only one option is specified. The checkpoint card block must be located within the SIMULATION block.

At least one of the following must be used:

TIMES <time_unit> <double> <double> . . . <double>
Specifies the points in time when checkpoint file output is desired, where <time_unit> indicates the units of the points in time, and <double> is each point in time. Any number of specific time points can be listed.
PERIODIC TIME <double> <time_unit>
Specifies a time interval for checkpoint file output, where <double> is the length of the time interval, and <time_unit> indicates the units of the time interval.
PERIODIC TIMESTEP <int>
Outputs checkpoint files every <int> number of timesteps. This option is identical to CHECKPOINT <int>.

## Optional Cards:¶

FORMAT <string>
Indicates the checkpoint file format. Only <string> = BINARY or HDF5 supported. If FORMAT is not specified, the default format is BINARY.

If a periodic timestep is chosen, checkpoint files will be named “pflotran-ts<int>.chk”, where “ts” stands for timestep, and <int> is the time step number when the file was printed. If a periodic time, or specific times were chosen, checkpoint files will be named “pflotran-<double><time_unit>.chk”, where <double> is the simulation time, and <time_unit> is the unit of time specified in the CHECKPOINT card block. If the simulation completes (i.e. it reaches the final time), an additional checkpoint file appended with “-restart.chk” will also be written, where one can increase the final time and pick up from where the simulation stopped.

## Examples¶

SIMULATION
SIMULATION_TYPE SUBSURFACE
PROCESS_MODELS
SUBSURFACE_FLOW flow
...
/
SUBSURFACE_TRANSPORT transport
...
/
/
CHECKPOINT
PERIODIC TIMESTEP 5
TIMES y 10. 20. 25. 50. 55.
FORMAT HDF5
/
RESTART restart.chk 0.
END