Miscellaneous Tools for PySPH¶
Input/Output of data files¶
The following functions are handy functions when processing output generated by PySPH or to generate new files.

pysph.solver.utils.
dump
(filename, particles, solver_data, detailed_output=False, only_real=True, mpi_comm=None, compress=False)[source]¶ Dump the given particles and solver data to the given filename.
Parameters:  filename (str) – Filename to dump to.
 particles (sequence(ParticleArray)) – Sequence of particle arrays to dump.
 solver_data (dict) – Additional information to dump about solver state.
 detailed_output (bool) – Specifies if all arrays should be dumped.
 only_real (bool) – Only dump the real particles.
 mpi_comm (mpi4pi.MPI.Intracomm) – An MPI communicator to use for parallel commmunications.
 compress (bool) – Specify if the file is to be compressed or not.
 mpi_comm is not passed or is set to None the local particles alone (If) –
 dumped, otherwise only rank 0 dumps the output. (are) –

pysph.solver.utils.
get_files
(dirname=None, fname=None, endswith=('hdf5', 'npz'))[source]¶ Get all solution files in a given directory, dirname.
Parameters:  dirname (str) – Name of directory.
 fname (str) – An initial part of the filename, if not specified use the first part of the dirname.
 endswith (str) – The extension of the file to load.

pysph.solver.utils.
load
(fname)[source]¶ Load the output data
Parameters: fname (str) – Name of the file or full path Examples
>>> data = load('elliptical_drop_100.npz') >>> data.keys() ['arrays', 'solver_data'] >>> arrays = data['arrays'] >>> arrays.keys() ['fluid'] >>> fluid = arrays['fluid'] >>> type(fluid) pysph.base.particle_array.ParticleArray >>> data['solver_data'] {'count': 100, 'dt': 4.6416394784204199e05, 't': 0.0039955855395528766}

pysph.solver.utils.
load_and_concatenate
(prefix, nprocs=1, directory='.', count=None)[source]¶ Load the results from multiple files.
Given a filename prefix and the number of processors, return a concatenated version of the dictionary returned via load.
Parameters:  prefix (str) – A filename prefix for the output file.
 nprocs (int) – The number of processors (files) to read
 directory (str) – The directory for the files
 count (int) – The file iteration count to read. If None, the last available one is read
Interpolator¶
This module provides a convenient class called
interpolator.Interpolator
which can be used to interpolate any
scalar values from the points onto either a mesh or a collection of other
points. SPH interpolation is performed with a simple Shepard filtering.

class
pysph.tools.interpolator.
InterpolateFunction
(dest, sources)[source]¶ Bases:
pysph.sph.equation.Equation
Parameters:  dest (str) – name of the destination particle array
 sources (list of str or None) – names of the source particle arrays

class
pysph.tools.interpolator.
InterpolateSPH
(dest, sources)[source]¶ Bases:
pysph.sph.equation.Equation
Parameters:  dest (str) – name of the destination particle array
 sources (list of str or None) – names of the source particle arrays

class
pysph.tools.interpolator.
Interpolator
(particle_arrays, num_points=125000, kernel=None, x=None, y=None, z=None, domain_manager=None, equations=None, method='shepard')[source]¶ Bases:
object
Convenient class to interpolate particle properties onto a uniform grid or given set of particles. This is particularly handy for visualization.
The x, y, z coordinates need not be specified, and if they are not, the bounds of the interpolated domain is automatically computed and num_points number of points are used in this domain uniformly placed.
Parameters:  particle_arrays (list) – A list of particle arrays.
 num_points (int) – the number of points to interpolate on to.
 kernel (Kernel) – the kernel to use for interpolation.
 x (ndarray) – the xcoordinate of points on which to interpolate.
 y (ndarray) – the ycoordinate of points on which to interpolate.
 z (ndarray) – the zcoordinate of points on which to interpolate.
 domain_manager (DomainManager) – An optional Domain manager for periodic domains.
 equations (sequence) – A sequence of equations or groups. Defaults to None. This is used only if the default interpolation equations are inadequate.
 method (str) – String with the following allowed methods: ‘shepard’, ‘sph’, ‘order1’

interpolate
(prop, comp=0)[source]¶ Interpolate given property.
Parameters:  prop (str) – The name of the property to interpolate.
 comp (int) – The component of the gradient required
Returns: Return type: A numpy array suitably shaped with the property interpolated.

set_domain
(bounds, shape)[source]¶ Set the domain to interpolate into.
Parameters:  bounds (tuple) – (xmin, xmax, ymin, ymax, zmin, zmax)
 shape (tuple) – (nx, ny, nz)

set_interpolation_points
(x=None, y=None, z=None)[source]¶ Set the points on which we must interpolate the arrays.
If any of x, y, z is not passed it is assumed to be 0.0 and shaped like the other nonNone arrays.
Parameters:  x (ndarray) – the xcoordinate of points on which to interpolate.
 y (ndarray) – the ycoordinate of points on which to interpolate.
 z (ndarray) – the zcoordinate of points on which to interpolate.

update
(update_domain=True)[source]¶ Update the NNPS when particles have moved.
If the update_domain is False, the domain is not updated.
Use this when the arrays are the same but the particles have themselves changed. If the particle arrays themselves change use the update_particle_arrays method instead.

update_particle_arrays
(particle_arrays)[source]¶ Call this for a new set of particle arrays which have the same properties as before.
For example, if you are reading the particle array data from files, each time you load a new file a new particle array is read with the same properties. Call this function to reset the arrays.

class
pysph.tools.interpolator.
SPHFirstOrderApproximation
(dest, sources, dim=1)[source]¶ Bases:
pysph.sph.equation.Equation
The method used to solve the linear system in this function is not same as in the reference. In the function Ax=b is solved where A := moment (Moment matrix) and b := p_sph (Property calculated using basic SPH). The calculation need the moment to be evaluated before this step which is done in SPHFirstOrderApproximationPreStep
References
[Liu2006] M.B. Liu, G.R. Liu, “Restoring particle consistency in smoothed particle hydrodynamics”, Applied Numerical Mathematics Volume 56, Issue 1 2006, Pages 1936, ISSN 01689274

class
pysph.tools.interpolator.
SPHFirstOrderApproximationPreStep
(dest, sources, dim=1)[source]¶ Bases:
pysph.sph.equation.Equation

pysph.tools.interpolator.
get_bounding_box
(particle_arrays, tight=False, stretch=0.05)[source]¶ Find the size of the domain given a sequence of particle arrays.
If tight is True, the bounds are tight, if not the domain is stretched along each dimension by an amount stretch specified as a percentage of the length along that dimension is added in each dimension.
SPH Evaluator¶
This module provides a class that allows one to evaluate a set of equations on a collection of particle arrays. This is very handy for nontrivial postprocessing that needs to be quick.
A convenience class that combines an AccelerationEval and an SPHCompiler to allow a user to specify particle arrays, equations, an optional domain and kernel to produce an SPH evaluation.
This is handy for postprocessing.

class
pysph.tools.sph_evaluator.
SPHEvaluator
(arrays, equations, dim, kernel=None, domain_manager=None, backend=None, nnps_factory=<type 'pysph.base.linked_list_nnps.LinkedListNNPS'>)[source]¶ Bases:
object
Constructor.
Parameters:  arrays (list(ParticleArray)) –
 equations (list) –
 dim (int) –
 kernel (kernel instance.) –
 domain_manager (DomainManager) –
 backend (str: indicates the backend to use.) – one of (‘opencl’, ‘cython’, ‘’, None)
 nnps_factory (A factory that creates an NNPSBase instance.) –

update
(update_domain=True)[source]¶ Update the NNPS when particles have moved.
If the update_domain is False, the domain is not updated.
Use this when the arrays are the same but the particles have themselves changed. If the particle arrays themselves change use the update_particle_arrays method instead.

update_particle_arrays
(arrays)[source]¶ Call this for a new set of particle arrays which have the same properties as before.
For example, if you are reading the particle array data from files, each time you load a new file a new particle array is read with the same properties. Call this function to reset the arrays.
STL Converter¶
The following function can be used to convert an STL file to a set of grid points.