.. _sec-expandhashall:

[ Expand Hash-all ] section
==================================================

This section is a preprocessing feature that automatically divides and then expands a background region containing **#all** mainly for air and vacuum.
Even without this feature, **#all** is automatically expanded internally by PHITS; however, that automatic expansion may make the number of regions excluded from a single cell excessively large, resulting in memory shortages or longer computation times.
In such a case, run PHITS with **icntl=18** using an input file containing **[expand hash-all]**.
The background region is then automatically divided, and the expanded result of **#all** is output in a form that excludes only the cells contained in each divided region.

Usage flow
--------------------------------------------------

The basic workflow is as follows.

#. Define a cell containing **#all** in the **[cell]** section.
#. Define mesh parameters and the output file name in the **[expand hash-all]** section.
#. Run PHITS with **icntl=18**.
#. Include the generated ``*_surface`` and ``*_cell`` files in the **[surface]** and **[cell]** sections using the ``infl`` command.
#. Comment out the definition of the original background region, namely the cell containing **#all**.
#. Reset **icntl=0** and run PHITS in the ordinary particle-transport mode.

Input format
--------------------------------------------------

.. code-block:: text

  [ Expand Hash-all ]
    mesh = xyz
    x-type = ...
    nx = ...
    xmin = ...
    xmax = ...
    y-type = ...
    ny = ...
    ymin = ...
    ymax = ...
    z-type = ...
    nz = ...
    zmin = ...
    zmax = ...
    file = expand_all.out
    margin = 1.0

    reg  xmin  xmax  ymin  ymax  zmin  zmax
    ...

.. rst-class:: no-caption-number

.. list-table:: Main parameters
   :header-rows: 1

   * - Item
     - Explanation
   * - **mesh**
     - Currently, only **xyz** can be specified.
   * - **x-type**, **nx**, **xmin**, **xmax**
     - Mesh definition in the x direction.
   * - **y-type**, **ny**, **ymin**, **ymax**
     - Mesh definition in the y direction.
   * - **z-type**, **nz**, **zmin**, **zmax**
     - Mesh definition in the z direction.
   * - **file**
     - Specifies the base output file name.
   * - **margin**
     - Margin added to the estimated bounding box in each direction. The default value is **1.0**.

The mesh parameters for each axis are specified in the same manner as an ordinary xyz mesh.
Among them, **mesh=xyz** and **file** are required.

Initial bounding-box table
--------------------------------------------------

If necessary, you can provide initial bounding boxes in a table at the end of the section.

.. code-block:: text

  reg  xmin  xmax  ymin  ymax  zmin  zmax
   10  -5.0   5.0  -2.0   2.0   0.0  10.0
   15   0.0   1.0   0.0   1.0   0.0   1.0

This table is useful when you want to give initial values for narrow regions or regions that are difficult to detect by sampling.
The columns are **reg xmin xmax ymin ymax zmin zmax**, and **reg** specifies the target cell number.

Generated files
--------------------------------------------------

Using the name specified by **file** as the base name, the following three kinds of files are generated.

1. A base file containing the bounding-box table
2. A ``*_surface`` file containing generated surface definitions
3. A ``*_cell`` file containing expanded cell definitions

The surface file contains generated **px**, **py**, and **pz** surfaces based on the estimated bounding boxes.
The cell file contains expanded cell definitions corresponding to cells containing **#all**.

Restrictions and notes
--------------------------------------------------

- This feature is available only when **icntl=18** is used.
- At present, **MPI parallel execution is not supported**. Use single or OpenMP execution.
- The target-cell search is limited to cells with **u=0**. Cells inside universes are not automatically searched.
- The cell containing **#all** itself is excluded from bounding-box estimation.
- If **margin** is too small, the estimated box may fail to cover the intended region near the boundary.

Input example
--------------------------------------------------

.. code-block:: text

  [ parameters ]
    icntl = 18

  [ cell ]
    1   0   -10
    2  -1   #all

  [ expand hash-all ]
    mesh = xyz
    x-type = 1
    nx = 20
    xmin = -100.0
    xmax = 100.0
    y-type = 1
    ny = 20
    ymin = -100.0
    ymax = 100.0
    z-type = 1
    nz = 20
    zmin = -100.0
    zmax = 100.0
    file = expand_all.out
    margin = 1.0

This input generates the bounding boxes and include files required to expand **#all**.