pmesh.transfer module

Deprecated since version 0.1.

class pmesh.transfer.TransferFunction[source]

Bases: object

these a a function of Window Transfer functions used by PM. they take the fourier-space field complex and the dimensionless circular frequency as inputs; complex is modified in-place.

some functions are factories: they return an actually window with the given parameter.

Working out the dimension of the input is important.

the output of Poisson introduces a dimension to rho_k! the output of SuperLanzcos introduces a dimension to rho_k!

w is a tuple of (w0, w1, w2, …) w is in circular frequency units. The dimensionful k is w * Nmesh / BoxSize (nyquist is at about w = pi) they broadcast to the correct shape of complex. This is to reduce memory usage somewhat. complex is modified in place.

static Constant(C)[source]
static Gaussian(smoothing)[source]

smoothing is in mesh units; Notice that this is different from the usual PM split convention. (used in Gadget2/3) The PM split is cut = sqrt(0.5) * smoothing

static Inspect(name, *indices)[source]

inspect the complex array at given indices mostly for debugging.

static Laplace(pm, complex)[source]

Take the Laplacian k-space: complex *= -w2

where this function performs only the -w **-2 part.

Note that k = w * Nmesh / BoxSize, thus the usual laplacian is

  • k ** 2 * complex = (Nmesh / BoxSize) ** 2 (-w**2) * complex
static NormalizeDC(pm, complex)[source]

removes the DC amplitude. This effectively divides by the mean

static Poisson(pm, complex)[source]

Solve Poisson equation in k-space: complex /= -w2

Notes about gravity:

gravity is

\phi_k = -4 \pi G \delta_k k^{-2}

where k = \omega N_m / L.

hence

\phi_k = -4 \pi G \delta_k \omega^{-2} (N_m / L)^{-2}

where this function performs only the - \omega **-2 part.

static PowerSpectrum(wout, psout)[source]

calculate the power spectrum. This shall be done after NormalizeDC and RemoveDC

static RemoveDC(pm, complex)[source]
static SuperLanzcos(dir, order=3)[source]

Super Lanzcos kernel of order 3. is complex * i * w in a fancier way.

Notice that for differentiation, one actually wants complex * i * k which is complex * i * w * Nmesh / BoxSize

static Trilinear(comm, complex, w)[source]