nbodykit.source.mesh.array

Classes

ArrayMesh(array, BoxSize[, comm, root]) A MeshSource initalized from an in-memory numpy array.
class nbodykit.source.mesh.array.ArrayMesh(array, BoxSize, comm=None, root=0, **kwargs)[source]

A MeshSource initalized from an in-memory numpy array.

Note

The in-memory array must be fully hosted by the root rank.

Parameters:
  • array (numpy.ndarray) – the numpy array holding the field data; this must be fully hosted by the rank specified by root
  • BoxSize (float, 3-vector) – the size of the box
  • root (int, optional) – the root rank holding the array data
  • **kwargs – additional meta-data to store
Attributes:
actions

A list of actions to apply to the density field when interpolating to the mesh.

attrs

A dictionary storing relevant meta-data about the CatalogSource.

Methods

apply(func[, kind, mode]) Return a view of the mesh, with actions updated to apply the specified function, either in Fourier space or configuration space, based on mode
compute([mode, Nmesh]) Compute / Fetch the mesh object into memory as a RealField or ComplexField object.
preview([axes, Nmesh, root]) Gather the mesh into as a numpy array, with (reduced) resolution.
save(output[, dataset, mode]) Save the mesh as a BigFileMesh on disk, either in real or complex space.
to_complex_field([out]) Convert the mesh source to the Fourier-space field, returning a pmesh.pm.ComplexField object.
to_field([mode, out]) Return the mesh as a pmesh Field object, either in Fourier space or configuration space, based on mode.
to_real_field() Convert the mesh source to the configuration-space field, returning a pmesh.pm.RealField object.
view() Return a “view” of the MeshSource, in the spirit of numpy’s ndarray view.
paint  
__finalize__(other)

Finalize the creation of a MeshSource object by copying over attributes from a second MeshSource.

Parameters:other (MeshSource) – the second MeshSource to copy over attributes from
__len__()

Length of a mesh source is zero

actions

A list of actions to apply to the density field when interpolating to the mesh.

This stores tuples of (mode, func, kind); see apply() for more details.

apply(func, kind='wavenumber', mode='complex')

Return a view of the mesh, with actions updated to apply the specified function, either in Fourier space or configuration space, based on mode

Parameters:
  • func (callable or a MeshFilter object) – func(x, y) where x is a list of r (k) values that broadcasts into a full array, when mode is ‘real’ (‘complex’); the value of x depends on kind. y is the value of the mesh field on the corresponding locations.
  • kind (string, optional) –

    if a MeshFilter object is given as func, this is ignored. The kind of value in x.

    • When mode is ‘complex’:
      • ’wavenumber’ means wavenumber from [- 2 pi / L * N / 2, 2 pi / L * N / 2).
      • ’circular’ means circular frequency from [- pi, pi).
      • ’index’ means [0, Nmesh )
    • When mode is ‘real’:
      • ’relative’ means distance from [-0.5 Boxsize, 0.5 BoxSize).
      • ’index’ means [0, Nmesh )
  • mode ('complex' or 'real', optional) – if a MeshFilter object is given as func, this is ignored. whether to apply the function to the mesh in configuration space or Fourier space
Returns:

a view of the mesh object with the actions attribute updated to include the new action

Return type:

MeshSource

attrs

A dictionary storing relevant meta-data about the CatalogSource.

compute(mode='real', Nmesh=None)

Compute / Fetch the mesh object into memory as a RealField or ComplexField object.

preview(axes=None, Nmesh=None, root=0)

Gather the mesh into as a numpy array, with (reduced) resolution. The result is broadcast to all ranks, so this uses \(\mathrm{Nmesh}^3\) per rank.

Parameters:
  • Nmesh (int, array_like) – The desired Nmesh of the result. Be aware this function allocates memory to hold a full Nmesh on each rank.
  • axes (int, array_like) – The axes to project the preview onto., e.g. (0, 1)
  • root (int, optional) – the rank number to treat as root when gathering to a single rank
Returns:

out – An numpy array holding the real density field.

Return type:

array_like

save(output, dataset='Field', mode='real')

Save the mesh as a BigFileMesh on disk, either in real or complex space.

Parameters:
  • output (str) – name of the bigfile file
  • dataset (str, optional) – name of the bigfile data set where the field is stored
  • mode (str, optional) – real or complex; the form of the field to store
to_complex_field(out=None)

Convert the mesh source to the Fourier-space field, returning a pmesh.pm.ComplexField object.

Not implemented in the base class, unless object is a view.

to_field(mode='real', out=None)

Return the mesh as a pmesh Field object, either in Fourier space or configuration space, based on mode.

This will call to_real_field() or to_complex_field() based on mode.

Parameters:mode ('real' or 'complex') – the return type of the field
Returns:either a RealField of ComplexField, storing the value of the field on the mesh
Return type:RealField, ComplexField
to_real_field()[source]

Convert the mesh source to the configuration-space field, returning a pmesh.pm.RealField object.

Not implemented in the base class, unless object is a view.

view()

Return a “view” of the MeshSource, in the spirit of numpy’s ndarray view.

This returns a new MeshSource whose memory is owned by self.

Note that for CatalogMesh objects, this is overidden by the CatalogSource.view function.