nbodykit.meshtools¶

Functions

SlabIterator(coords[, axis, symmetry_axis])

Iterate over the specified dimension of the coordinate mesh, returning a MeshSlab for each iteration

Classes

MeshSlab(islab, coords, axis, symmetry_axis)

A convenience class to represent a specific slab of a mesh, which is denoted as a slab

class nbodykit.meshtools.MeshSlab(islab, coords, axis, symmetry_axis)[source]¶

A convenience class to represent a specific slab of a mesh, which is denoted as a slab

Attributes

hermitian_symmetric: Whether the slab is Hermitian-symmetric
hermitian_weights: Weights to be applied to quantities on the slab in order
index: Return an indexing list appropriate for selecting the slicing the
meshshape: Return the local shape of the mesh on this rank, as determined
nonsingular: The indices on the slab of the positive frequencies along the dimension specified by symmetry_axis.
shape: Return the shape of the slab

Methods

`coords`(i)	Return the coordinate array for dimension `i` on this slab,
`mu`(los)	The mu value defined at each point on the slab for the specified line-of-sight index
`norm2`()	The square of coordinate grid norm defined at each point on the slab.

__init__(islab, coords, axis, symmetry_axis)[source]¶

Parameters

islab (int, [0, x[0].shape[0]]) – the index of the slab, which indexes the first dimension of the mesh (the x coordinate), thus producing a y-z plane
coords (list of arrays) – the coordinate arrays of the mesh, with proper 3D shapes for easy broadcasting; if the mesh has size (Nx, Ny, Nz), then the shapes of x are: [(Nx, 1, 1), (1, Ny, 1), (1, 1, Nz)]
axis (int, {0, 1, 2}) – the index of the mesh axis to iterate over
symmetry_axis (int, optional) – if provided, the axis that has been compressed due to Hermitian symmetry

coords(i)[source]¶

Return the coordinate array for dimension i on this slab,

Note

The return value will be properly squeezed for easy broadcasting, i.e., if i is self.axis, then an array of shape (1,1) array is returned, otherwise, the shape is (N_i, 1) or (1, N_i)

Parameters: i (int, {0,1,2}) – the index of the desired dimension
Returns: the coordinate array for dimension i on the slab; see the note about the shape of the return array for details
Return type: array_like

property hermitian_symmetric¶: Whether the slab is Hermitian-symmetric

property hermitian_weights¶

Weights to be applied to quantities on the slab in order to account for Hermitian symmetry

These weights double-count the positive frequencies along the symmetry_axis.

property index¶: Return an indexing list appropriate for selecting the slicing the appropriate slab out of a full 3D array of shape (Nx, Ny, Nz)

property meshshape¶: Return the local shape of the mesh on this rank, as determined by the input coordinates array

mu(los)[source]¶

The mu value defined at each point on the slab for the specified line-of-sight index

Parameters: los (array_like,) – the direction of the line-of-sight, which mu is defined with respect to; must have a norm of 1.
Returns: the mu value at each point in the slab
Return type: array_like, (slab.shape)

property nonsingular¶

The indices on the slab of the positive frequencies along the dimension specified by symmetry_axis.

This takes advantage of the fact that pmesh.pm.ComplexField shifts the Nyquist frequencies to the negative halves. Therefore this ensures that the zero and Nyquist planes perpendicular to the symmetry axis have weight 1, whereas other modes have weight 2.

Returns: idx – Return a boolean array with the shape of the slab, with True elements giving the elements with positive freq along symmetry_axis
Return type: array_like, self.shape

norm2()[source]¶

The square of coordinate grid norm defined at each point on the slab.

This broadcasts the coordinate arrays along each dimension to compute the norm at each point in the slab.

Returns: the square of coordinate mesh at each point in the slab
Return type: array_like, (slab.shape)

property shape¶: Return the shape of the slab

nbodykit.meshtools.SlabIterator(coords, axis=0, symmetry_axis=None)[source]¶

Iterate over the specified dimension of the coordinate mesh, returning a MeshSlab for each iteration

Parameters

coords (list of arrays) – the coordinate arrays of the mesh, with proper 3D shapes for easy broadcasting; if the mesh has size (Nx, Ny, Nz), then the shapes of x3d should be: [(Nx, 1, 1), (1, Ny, 1), (1, 1, Nz)]
axis (int, optional) – the index of the mesh axis to iterate over
symmetry_axis (int, optional) – if provided, the axis that has been compressed due to Hermitian symmetry