.. _input_reference:

Input File Reference
====================

Every ExaGOOP simulation requires two input files: a plain-text **input
parameter file** (the ``*.inp`` file read by AMReX's ParmParse)
and a **particle file** containing the initial material point data. Both are
typically generated by the PreProcess scripts in each test directory; this
page documents every supported parameter so that you can construct or modify
them by hand.

.. note::

   Parameters marked **required** have no default and will cause ExaGOOP to
   abort if absent. Parameters marked *optional* have defaults listed in the
   Default column.

Running the solver
------------------

.. code-block:: bash

   ./ExaGOOP<dim>d.<suffix>.ex inputs.inp
   # or with MPI:
   mpirun -n 4 ./ExaGOOP<dim>d.<suffix>.ex inputs.inp


Particle File Format
--------------------

ExaGOOP accepts particle files in ASCII (plain text) or HDF5 format. The
format is auto-detected from the file extension: ``.dat`` or ``.inp`` files
are treated as ASCII; ``.h5`` files as HDF5.

ASCII format
~~~~~~~~~~~~

The file begins with two header lines followed by a comment line listing the
column names, then one data row per material point:

.. code-block:: text

   dim: <N>
   number_of_material_points: <M>
   # phase x [y] [z]  vx [vy] [vz]  radius  density  <cm_cols>  [T spheat thermcond heatsrc]
   0  0.25  0.0  0.0  0.0  0.0  0.0  0.125  1000.0  ...

Column order depends on dimensionality and the constitutive model:

.. list-table::
   :header-rows: 1
   :widths: 20 15 65

   * - Column
     - Type
     - Description
   * - ``phase``
     - int
     - Material phase index (0 for standard deformable material)
   * - ``x``, ``y``, ``z``
     - real
     - Initial position coordinates (m). ``y`` and ``z`` omitted in 1-D and 2-D.
   * - ``vx``, ``vy``, ``vz``
     - real
     - Initial velocity components (m/s). ``vy``, ``vz`` omitted in lower dimensions.
   * - ``radius``
     - real
     - Particle radius used for neighbour searches (m). Typically set to half the inter-particle spacing.
   * - ``density``
     - real
     - Material density :math:`\rho_0` (kg/m³).
   * - ``E``, ``nu``
     - real
     - Young's modulus (Pa) and Poisson's ratio (–). Present when ``constitutive_model.type = elastic``.
   * - ``Bulk_modulus``, ``Gama_pressure``, ``Dynamic_viscosity``
     - real
     - Bulk modulus (Pa), pressure ratio :math:`\Gamma` (–), dynamic viscosity (Pa·s). Present when ``constitutive_model.type = fluid``.
   * - ``T``
     - real
     - Initial temperature (K). Present only when compiled with ``USE_TEMP=1``.
   * - ``spheat``
     - real
     - Specific heat capacity :math:`c_p` (J/(kg·K)). Present only with ``USE_TEMP=1``.
   * - ``thermcond``
     - real
     - Thermal conductivity :math:`k` (W/(m·K)). Present only with ``USE_TEMP=1``.
   * - ``heatsrc``
     - real
     - Volumetric internal heat source :math:`\dot{q}` (W/m³). Present only with ``USE_TEMP=1``.

HDF5 format
~~~~~~~~~~~

The HDF5 file stores the same columns as individual 1-D datasets under the
root group, plus scalar attributes ``dim`` and ``number_of_material_points``.
Dataset names are identical to the ASCII column names above.


Input Parameter File
--------------------

Parameters are grouped into namespaces. Each line has the form::

   namespace.parameter_name  =  value

Lines beginning with ``#`` are comments.

``mpm.`` namespace — Domain and Grid
--------------------------------------

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``mpm.prob_lo``
     - real[]
     - **required**
     - Lower corner of the computational domain (m). Three values always; unused dimensions set to 0.
   * - ``mpm.prob_hi``
     - real[]
     - **required**
     - Upper corner of the computational domain (m).
   * - ``mpm.ncells``
     - int[]
     - **required**
     - Number of background grid cells per direction. Unused dimensions set to 0.
   * - ``mpm.max_grid_size``
     - int
     - 8
     - Maximum AMReX box size. Must be greater than 1.
   * - ``mpm.is_it_periodic``
     - int[]
     - **required**
     - Periodicity flag per direction: ``1`` = periodic, ``0`` = non-periodic.

``mpm.`` namespace — Time Control
------------------------------------

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``mpm.final_time``
     - real
     - **required**
     - Simulation end time (s).
   * - ``mpm.max_steps``
     - int
     - **required**
     - Maximum number of time steps. The run stops at whichever limit is reached first.
   * - ``mpm.fixed_timestep``
     - int
     - 0
     - If ``1``, use a fixed time step supplied via ``mpm.timestep`` instead of the CFL-adaptive step.
   * - ``mpm.timestep``
     - real
     - —
     - Fixed time step size (s). Required when ``fixed_timestep = 1``.
   * - ``mpm.CFL``
     - real
     - 0.1
     - CFL number for adaptive time stepping. Ignored when ``fixed_timestep = 1``.
   * - ``mpm.dt_min_limit``
     - real
     - 1e-12
     - Minimum allowable adaptive time step (s). ExaGOOP aborts if the step falls below this.
   * - ``mpm.dt_max_limit``
     - real
     - 1.0
     - Maximum allowable adaptive time step (s).

``mpm.`` namespace — Physics
-------------------------------

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``mpm.gravity``
     - real[]
     - ``0.0 -9.81 0.0``
     - Gravitational acceleration vector (m/s²).
   * - ``mpm.alpha_pic_flip``
     - real
     - 0.95
     - PIC/FLIP blending factor. ``0.0`` = pure PIC (maximum dissipation), ``1.0`` = pure FLIP (minimum dissipation).
   * - ``mpm.order_scheme``
     - int
     - 1
     - Shape function order: ``1`` = bilinear, ``2`` = quadratic B-spline, ``3`` = cubic B-spline.
   * - ``mpm.stress_update_scheme``
     - string
     - ``USL``
     - Stress update scheme: ``USL`` (Update Stress Last) or ``MUSL`` (Modified USL).
   * - ``mpm.calculate_strain_based_on_delta``
     - int
     - 0
     - If ``1``, compute strain from incremental displacement rather than velocity gradient.
   * - ``mpm.mass_tolerance``
     - real
     - 1e-8
     - Grid nodes whose lumped mass falls below this threshold are excluded from the nodal velocity update.
   * - ``mpm.applied_strainrate``
     - real
     - 0.0
     - Uniform applied strain rate (1/s). Applied to the entire domain.
   * - ``mpm.applied_strainrate_time``
     - real
     - ``final_time``
     - Duration over which the applied strain rate is active (s).
   * - ``mpm.external_loads``
     - int
     - 0
     - If ``1``, apply a uniform body force to the slab region defined below.
   * - ``mpm.force_slab_lo``
     - real[]
     - —
     - Lower corner of the force slab (m). Required when ``external_loads = 1``.
   * - ``mpm.force_slab_hi``
     - real[]
     - —
     - Upper corner of the force slab (m). Required when ``external_loads = 1``.
   * - ``mpm.extforce``
     - real[]
     - —
     - Force per unit volume applied within the slab (N/m³). Required when ``external_loads = 1``.

``mpm.`` namespace — Material Points
--------------------------------------

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``mpm.particle_file``
     - string
     - ``mpm_particles.dat``
     - Path to the particle input file. Used when ``use_autogen = 0``.
   * - ``mpm.num_redist``
     - int
     - 10
     - Redistribute particles across MPI ranks every N time steps.
   * - ``mpm.use_autogen``
     - int
     - 0
     - If ``1``, generate particles internally from the autogen parameters below instead of reading a file.

When ``use_autogen = 1``, the following parameters define the particle block:

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``mpm.mincoords_autogen``
     - real[]
     - **required**
     - Lower corner of the autogen particle block (m).
   * - ``mpm.maxcoords_autogen``
     - real[]
     - **required**
     - Upper corner of the autogen particle block (m).
   * - ``mpm.vel_autogen``
     - real[]
     - **required**
     - Initial velocity for all autogen particles (m/s).
   * - ``mpm.ppc``
     - int[]
     - —
     - Particles per cell per direction, e.g. ``2 2 2`` for eight particles per cell in 3-D.
   * - ``mpm.multi_part_per_cell_autogen``
     - int
     - 1
     - If ``1``, place multiple particles per cell (uses ``ppc``); if ``0``, one particle per cell.
   * - ``mpm.constmodel_autogen``
     - int
     - 1
     - Constitutive model ID: ``0`` = linear elastic, ``1`` = compressible fluid.
   * - ``mpm.dens_autogen``
     - real
     - 1000.0
     - Density of autogen particles (kg/m³).
   * - ``mpm.E_autogen``
     - real
     - 1e9
     - Young's modulus for elastic model (Pa).
   * - ``mpm.nu_autogen``
     - real
     - 0.1
     - Poisson's ratio for elastic model (–).
   * - ``mpm.bulkmod_autogen``
     - real
     - 0.0
     - Bulk modulus for fluid model (Pa).
   * - ``mpm.Gama_pres_autogen``
     - real
     - 1.4
     - Pressure ratio :math:`\Gamma` for the fluid equation of state (–).
   * - ``mpm.visc_autogen``
     - real
     - 0.001
     - Dynamic viscosity for fluid model (Pa·s).
   * - ``mpm.T_autogen``
     - real
     - 0.0
     - Initial temperature of autogen particles (K). ``USE_TEMP`` only.
   * - ``mpm.cp_autogen``
     - real
     - 1.0
     - Specific heat capacity (J/(kg·K)). ``USE_TEMP`` only.
   * - ``mpm.thermcond_autogen``
     - real
     - 1.0
     - Thermal conductivity (W/(m·K)). ``USE_TEMP`` only.
   * - ``mpm.heatsrc_autogen``
     - real
     - 0.0
     - Volumetric internal heat source (W/m³). ``USE_TEMP`` only.

``mpm.`` namespace — Output
-----------------------------

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``mpm.write_output_time``
     - real
     - ``final_time / 10``
     - Interval between solution snapshots (s).
   * - ``mpm.screen_output_time``
     - real
     - ``write_output_time / 10``
     - Interval between screen (terminal) output lines (s).
   * - ``mpm.prefix_particlefilename``
     - string
     - ``plt``
     - Directory/file prefix for particle output plotfiles (``plt*``).
   * - ``mpm.prefix_gridfilename``
     - string
     - ``plt``
     - Directory/file prefix for nodal grid output plotfiles (``nplt*``).
   * - ``mpm.prefix_densityfilename``
     - string
     - ``plt``
     - Directory/file prefix for density output plotfiles.
   * - ``mpm.prefix_checkpointfilename``
     - string
     - ``chk``
     - Directory/file prefix for checkpoint files used to restart a run.
   * - ``mpm.prefix_asciifilename``
     - string
     - ``matpnt``
     - Directory/file prefix for ASCII material point output files.
   * - ``mpm.diagnostic_output_folder``
     - string
     - ``./Diagnostics/``
     - Directory for diagnostic output files.
   * - ``mpm.num_of_digits_in_filenames``
     - int
     - 6
     - Number of zero-padded digits in output file step indices.
   * - ``mpm.write_ascii``
     - int
     - 0
     - If ``1``, write ASCII material point files alongside the plotfiles.

``mpm.`` namespace — Diagnostics
----------------------------------

Diagnostics are activated by setting ``mpm.print_diagnostics = 1``.

.. list-table::
   :header-rows: 1
   :widths: 36 10 12 42

   * - Parameter
     - Type
     - Default
     - Description
   * - ``mpm.print_diagnostics``
     - int
     - 0
     - Master switch: set to ``1`` to enable all diagnostic output.
   * - ``mpm.do_calculate_tke_tse``
     - int
     - 0
     - If ``1``, compute and write total kinetic and strain energies.
   * - ``mpm.do_calculate_mwa_velcomp``
     - int
     - 0
     - If ``1``, compute and write mass-weighted average velocity components.
   * - ``mpm.do_calculate_mwa_velmag``
     - int
     - 0
     - If ``1``, compute and write mass-weighted average velocity magnitude.
   * - ``mpm.do_calculate_minmaxpos``
     - int
     - 0
     - If ``1``, compute and write the minimum and maximum particle positions.
   * - ``mpm.write_diag_output_time``
     - real
     - ``write_output_time``
     - Interval between diagnostic output writes (s).

``mpm.`` namespace — Level-Set Output
-----------------------------------------

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``mpm.levset_output``
     - int
     - 0
     - If ``1``, write level-set field plotfiles for visualisation.
   * - ``mpm.levset_smoothfactor``
     - real
     - 1.0
     - Smoothing factor applied to the level-set signed-distance field.
   * - ``mpm.levset_gridratio``
     - int
     - 1
     - Refinement ratio for the level-set grid relative to the background grid.

``mpm.`` namespace — Momentum Boundary Conditions
---------------------------------------------------

Momentum BCs are specified per face. Valid face identifiers are ``xlo``,
``xhi``, ``ylo``, ``yhi``, ``zlo``, ``zhi``.

.. code-block:: text

   mpm.bc_<face>_mom  =  <type>

Valid ``<type>`` values:

.. list-table::
   :header-rows: 1
   :widths: 25 75

   * - Value
     - Behaviour
   * - ``slip``
     - Slip wall (default): zero normal velocity, unconstrained tangential velocity.
   * - ``noslip``
     - No-slip wall: all velocity components set to zero (or the prescribed wall velocity).
   * - ``partialslip``
     - Partial-slip wall: tangential velocity damped by friction coefficient ``wall_mu``.
   * - ``outflow``
     - Outflow: material points exiting through this face are removed.
   * - ``periodic``
     - Periodic. Must be matched with the opposite face and ``mpm.is_it_periodic = 1`` in that direction.

Additional sub-parameters for ``mpm.bc_<face>_mom``:

.. list-table::
   :header-rows: 1
   :widths: 36 10 12 42

   * - Parameter
     - Type
     - Default
     - Description
   * - ``mpm.bc_<face>_mom.wall_vel``
     - real[]
     - ``0 0 0``
     - Prescribed constant wall velocity (m/s) for ``noslip`` or ``partialslip`` walls.
   * - ``mpm.bc_<face>_mom.wall_mu``
     - real
     - 0.0
     - Friction coefficient for ``partialslip`` walls (–).
   * - ``mpm.bc_<face>_mom.udf_lib``
     - string
     - —
     - Path to the shared library implementing a UDF velocity profile. Both ``udf_lib`` and ``udf_func`` must be supplied together.
   * - ``mpm.bc_<face>_mom.udf_func``
     - string
     - —
     - Name of the C-linkage function exported by the UDF shared library. See :ref:`udf_moving_wall` for the required function signature.

``mpm.`` namespace — Temperature Boundary Conditions (``USE_TEMP`` only)
--------------------------------------------------------------------------

Temperature BCs follow the same per-face pattern as momentum BCs.

.. code-block:: text

   mpm.bc_<face>_temp  =  <type>

Valid ``<type>`` values:

.. list-table::
   :header-rows: 1
   :widths: 20 80

   * - Value
     - Behaviour
   * - ``adiabatic``
     - Adiabatic (default): zero heat flux through the face.
   * - ``dirichlet``
     - Fixed wall temperature. Requires ``T_wall``.
   * - ``heatflux``
     - Prescribed heat flux. Requires ``flux``.
   * - ``convective``
     - Newton cooling law: :math:`q = h (T_\text{wall} - T_\infty)`. Requires ``h`` and ``T_inf``.
   * - ``periodic``
     - Periodic (must be paired with ``mpm.is_it_periodic = 1`` in that direction).

Additional sub-parameters for ``mpm.bc_<face>_temp``:

.. list-table::
   :header-rows: 1
   :widths: 36 10 12 42

   * - Parameter
     - Type
     - Default
     - Description
   * - ``mpm.bc_<face>_temp.T_wall``
     - real
     - 0.0
     - Wall temperature for ``dirichlet`` BC (K).
   * - ``mpm.bc_<face>_temp.flux``
     - real
     - 0.0
     - Prescribed heat flux for ``heatflux`` BC (W/m²). Positive flux into the domain.
   * - ``mpm.bc_<face>_temp.h``
     - real
     - 0.0
     - Convective heat transfer coefficient for ``convective`` BC (W/(m²·K)).
   * - ``mpm.bc_<face>_temp.T_inf``
     - real
     - 0.0
     - Ambient temperature for ``convective`` BC (K).
   * - ``mpm.bc_<face>_temp.udf_lib``
     - string
     - —
     - Path to a UDF shared library for a custom temperature profile.
   * - ``mpm.bc_<face>_temp.udf_func``
     - string
     - —
     - Function name in the UDF temperature shared library.

``amr.`` namespace — Restart
------------------------------

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``amr.restart_checkfile``
     - string
     - ``""``
     - Path to a checkpoint directory to restart the simulation from. Leave empty for a fresh start.

``eb2.`` namespace — Embedded Boundaries (``USE_EB`` only)
-----------------------------------------------------------

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``eb2.body_names``
     - string[]
     - —
     - Space-separated list of body names. Each name becomes the ParmParse namespace for that body's parameters. If omitted, ExaGOOP falls back to legacy single-body mode reading from the ``eb2.`` namespace directly.

Per-body namespace ``<body_name>.`` (``USE_EB`` only)
------------------------------------------------------

Replace ``<body_name>`` with the name listed in ``eb2.body_names``.

**Common parameters (all geometry types):**

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``<name>.geom_type``
     - string
     - **required**
     - Shape type: ``sphere``, ``plane``, ``cylinder``, ``box``, ``stl``, ``udf_cpp``, ``wedge_hopper``.
   * - ``<name>.ls_refinement``
     - int
     - 1
     - Level-set grid refinement ratio relative to the background grid. Higher values improve surface accuracy.
   * - ``<name>.levelset_mom``
     - string
     - ``noslipwall``
     - Momentum BC on the body surface: ``noslipwall``, ``slipwall``, or ``partialslip``.
   * - ``<name>.lset_wall_mu``
     - real
     - 0.0
     - Friction coefficient for ``partialslip`` body surfaces (–).
   * - ``<name>.lset_wall_vel``
     - real[]
     - ``0 0 0``
     - Constant wall velocity imposed on the body surface (m/s).
   * - ``<name>.temp_bc_type``
     - string
     - ``adiabatic``
     - Temperature BC on the body surface: ``isothermal``, ``adiabatic``, ``heatflux``, ``convective``. ``USE_TEMP`` only.
   * - ``<name>.lset_T_wall``
     - real
     - 0.0
     - Isothermal wall temperature (K). ``USE_TEMP`` only.
   * - ``<name>.lset_heat_flux``
     - real
     - 0.0
     - Heat flux through the body surface (W/m²). ``USE_TEMP`` only.
   * - ``<name>.lset_h_conv``
     - real
     - 0.0
     - Convective heat transfer coefficient (W/(m²·K)). ``USE_TEMP`` only.
   * - ``<name>.lset_T_inf``
     - real
     - 0.0
     - Ambient temperature for convective BC (K). ``USE_TEMP`` only.

**Sphere** (``geom_type = sphere``):

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``<name>.sphere_radius``
     - real
     - **required**
     - Sphere radius (m).
   * - ``<name>.sphere_center``
     - real[]
     - **required**
     - Centre coordinates (m).
   * - ``<name>.sphere_has_fluid_inside``
     - bool
     - ``false``
     - If ``true``, fluid occupies the interior of the sphere; the solid body is outside.

**Plane** (``geom_type = plane``):

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``<name>.plane_point``
     - real[]
     - **required**
     - A point on the plane (m).
   * - ``<name>.plane_normal``
     - real[]
     - **required**
     - Outward normal vector pointing into the fluid domain.
   * - ``<name>.plane_has_fluid_inside``
     - bool
     - ``false``
     - Orientation flag. See ``sphere_has_fluid_inside``.

**Cylinder** (``geom_type = cylinder``):

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``<name>.cylinder_radius``
     - real
     - **required**
     - Cylinder radius (m).
   * - ``<name>.cylinder_center``
     - real[]
     - **required**
     - Axis centre coordinates (m).
   * - ``<name>.cylinder_height``
     - real
     - 1.0
     - Cylinder height along the axis direction (m).
   * - ``<name>.cylinder_direction``
     - int
     - 2
     - Axis direction: ``0`` = x, ``1`` = y, ``2`` = z.
   * - ``<name>.cylinder_has_fluid_inside``
     - bool
     - ``false``
     - Orientation flag.

**Box** (``geom_type = box``):

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``<name>.box_lo``
     - real[]
     - **required**
     - Lower corner of the box (m).
   * - ``<name>.box_hi``
     - real[]
     - **required**
     - Upper corner of the box (m).
   * - ``<name>.box_has_fluid_inside``
     - bool
     - ``false``
     - Orientation flag.

**STL geometry** (``geom_type = stl``):

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``<name>.stl_file``
     - string
     - **required**
     - Path to an STL surface mesh file describing the body geometry.

**UDF implicit function** (``geom_type = udf_cpp``):

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``<name>.udf_so_file``
     - string
     - **required**
     - Path to a shared library exporting a signed-distance function for the body surface.

**Wedge hopper** (``geom_type = wedge_hopper``, 3-D only):

Parameters are read from the ``wedge_hopper.`` namespace rather than the body namespace:

.. list-table::
   :header-rows: 1
   :widths: 32 10 15 43

   * - Parameter
     - Type
     - Default
     - Description
   * - ``wedge_hopper.exit_size``
     - real
     - **required**
     - Width of the hopper exit opening (m).
   * - ``wedge_hopper.bin_size``
     - real
     - **required**
     - Width of the hopper bin above the funnel (m).
   * - ``wedge_hopper.funnel_height``
     - real
     - **required**
     - Height of the converging funnel section (m).
   * - ``wedge_hopper.vertical_offset``
     - real
     - domain centre
     - Vertical position of the hopper centre (m).


Minimal Working Example
------------------------

The following input file runs a 1-D elastic bar vibration with 30 cells,
no gravity, and fixed boundary conditions at both ends:

.. code-block:: text

   #------------------------------
   # Domain
   #------------------------------
   mpm.prob_lo        = 0.0 0.0 0.0
   mpm.prob_hi        = 30.0 0.0 0.0
   mpm.ncells         = 30 0 0
   mpm.max_grid_size  = 16
   mpm.is_it_periodic = 0

   #------------------------------
   # Time control
   #------------------------------
   mpm.final_time  = 50.0
   mpm.max_steps   = 5000000
   mpm.CFL         = 0.1

   #------------------------------
   # Material points
   #------------------------------
   mpm.particle_file = mpm_particles.dat

   #------------------------------
   # Output
   #------------------------------
   mpm.write_output_time  = 0.5
   mpm.screen_output_time = 0.001
   mpm.prefix_particlefilename = "results/plt"
   mpm.prefix_gridfilename     = "results/nplt"

   #------------------------------
   # Numerics
   #------------------------------
   mpm.order_scheme           = 1
   mpm.alpha_pic_flip         = 1.0
   mpm.stress_update_scheme   = MUSL
   mpm.gravity                = 0.0 0.0 0.0

   #------------------------------
   # Boundary conditions
   #------------------------------
   mpm.bc_xlo_mom = noslip
   mpm.bc_xhi_mom = noslip