.. role:: cpp(code)
  :language: c++

.. _sec:Checkpoint:

********************
Checkpoint / Restart
********************
.. toctree::
   :maxdepth: 1

REMORA has a standard sort of checkpointing and restarting capability and
uses the native AMReX format for reading and writing checkpoints.
In the inputs file, the following options control the generation of
checkpoint files (which are really directories):

Writing the Checkpoint "Files"
==============================

.. _list-of-parameters-8:

List of Parameters
------------------

+----------------------------------+-----------------------------------+----------------+----------------+
| Parameter                        | Definition                        | Acceptable     | Default        |
|                                  |                                   | Values         |                |
+==================================+===================================+================+================+
| **remora.check_file**            | prefix for                        | String         | ``chk``        |
|                                  | restart files                     |                |                |
+----------------------------------+-----------------------------------+----------------+----------------+
| **remora.check_int**             | how often (by                     | Integer        | -1             |
|                                  | level-0 time                      | :math:`> 0`    |                |
|                                  |                                   |                |                |
|                                  | steps) to                         |                |                |
|                                  | write restart                     |                |                |
|                                  |                                   |                |                |
|                                  | files                             |                |                |
+----------------------------------+-----------------------------------+----------------+----------------+
| **remora.check_int_time**        | how often (in simulation time     | Real           | -1.0           |
|                                  |                                   | :math:`> 0`    |                |
|                                  | in seconds) to write restart      |                |                |
|                                  | files                             |                |                |
+----------------------------------+-----------------------------------+----------------+----------------+
| **remora.file_min_digits**       | Minimum number of digits          | Integer >= 0   | 5              |
|                                  |                                   |                |                |
|                                  | in iteration number appended to   |                |                |
|                                  |                                   |                |                |
|                                  | plotfile and checkpoint files     |                |                |
+----------------------------------+-----------------------------------+----------------+----------------+

Note: If both ``check_int`` and ``check_int_time`` are set, plotfile output will occur ``check_int`` steps or
``check_int_time`` simulation seconds after the last plotfile, whichever happens first.

Restarting
==========

+----------------------------------+----------------+----------------+----------------+
| Parameter                        | Definition     | Acceptable     | Default        |
|                                  |                | Values         |                |
+==================================+================+================+================+
| **remora.restart**               | name of the    | String         | not used if    |
|                                  | file           |                | not set        |
|                                  | (directory)    |                |                |
|                                  |                |                |                |
|                                  | from which to  |                |                |
|                                  | restart        |                |                |
|                                  | files          |                |                |
+----------------------------------+----------------+----------------+----------------+

.. _examples-of-usage-7:

Examples of Usage
-----------------

-  **remora.check_file** = ``chk_run``

-  **remora.check_int** = 10

   means that restart files (really directories) starting with the
   prefix “*chk_run*” will be generated every 10 level-0 time steps. The
   directory names will be ``chk_run00000``, ``chk_run00010``,
   ``chk_run00020``, etc.

To restart from ``chk_run00061``,for example, then set

-  **remora.restart** = ``chk_run00061``