cogwheel.likelihood.relative_binning

Implementation of the relative binning algorithm for fast likelihood evaluation.

Valid for frequency domain waveforms, if these have higher harmonics these must be given in the coprecessing frame. Splines of arbitrary degree are used to interpolate the ratio between an arbitrary waveform and a reference waveform.

Three classes are provided: BaseRelativeBinningLikelihood, BaseLinearFree and RelativeBinningLikelihood:

BaseRelativeBinningLikelihood is an abstract class, intended for subclassing. It provides the infrastructure to set up the relative-binning frequency bins and basis splines but does not make assumptions about which waveform is used to heterodyne the data or how. This is done by the method _set_summary which the subclass must provide.

RelativeBinningLikelihood is one such concrete subclass. Its method lnlike computes the log likelihood using relative binning.

BaseLinearFree is another base classs that extends BaseRelativeBinningLikelihood with functionality for computing the time shift that best aligns an arbitrary waveform with the reference waveform, to remove correlations between time and intrinsic parameters (we call this convention “linear-free” because the phase difference as a function of frequency has no linear correlation).

Classes

BaseLinearFree	Define a method ._get_linearfree_hplus_hcross_dt to compute linear-free waveforms and the timeshift required to go back to the approximant's convention.
BaseRelativeBinning	Abstract class that implements general relative binning methods.
RelativeBinningLikelihood	Generalization of CBCLikelihood that implements computation of likelihood with the relative binning method (fast).