Utilities¶

Provides a collection of functions useful for using/mixing PRISM with other applications.

prism.utils.get_hybrid_lnpost_fn(lnpost_fn, pipeline_obj, *, emul_i=None, unit_space=False, impl_prior=True, par_dict=False)[source]¶

Returns a function definition hybrid_lnpost(par_set, *args, **kwargs).

This hybrid_lnpost() function can be used to calculate the natural logarithm of the posterior probability, which analyzes a given par_set first in the provided pipeline_obj at iteration emul_i and passes it to lnpost_fn if it is plausible.

This function needs to be called by all MPI ranks.

Other Parameters:
Parameters:	lnpost_fn (function) – Function definition that needs to be called if the provided par_set is plausible in iteration emul_i of pipeline_obj. The used call signature is `lnpost_fn(par_set, args, kwargs)`. All MPI ranks will call this function unless called within the `worker_mode` context manager. pipeline_obj* (`Pipeline` object) – The instance of the `Pipeline` class that needs to be used for determining the validity of the proposed sampling step.
	emul_i (int or None. Default: None) – If int, number indicating the requested emulator iteration. If None, the last iteration of the emulator will be used. unit_space (bool. Default: False) – Bool determining whether or not par_set will be given in unit space. impl_prior (bool. Default: True) – Bool determining whether or not the hybrid_lnpost() function should use the implausibility values of a given par_set as an additional prior. par_dict (bool. Default: False) – Bool determining whether or not par_set will be an array_like (False) or a dict (True).
Returns:	hybrid_lnpost (function) – Definition of the function `hybrid_lnpost(par_set, args, *kwargs)`.

See also

get_walkers(): Analyzes proposed init_walkers and returns valid p0_walkers.
worker_mode: Special context manager within which all code is executed in worker mode.

Note

The input arguments unit_space and par_dict state in what form par_set will be provided to the hybrid_lnpost() function, such that it can be properly converted to the format used in Pipeline. The par_set that is passed to lnpost_fn is unchanged.

Warning

Calling this function factory will disable all regular logging in pipeline_obj (do_logging set to False), in order to avoid having the same message being logged every time hybrid_lnpost() is called.

prism.utils.get_walkers(pipeline_obj, *, emul_i=None, init_walkers=None, req_n_walkers=None, unit_space=False, lnpost_fn=None, **kwargs)[source]¶

Analyzes proposed init_walkers and returns plausible p0_walkers.

Analyzes sample set init_walkers in the provided pipeline_obj at iteration emul_i and returns all samples that are plausible to be used as starting positions for MCMC walkers. The provided samples and returned walkers should be/are given in unit space if unit_space is True.

If init_walkers is None, returns impl_sam instead if it is available.

This function needs to be called by all MPI ranks.

Parameters:

pipeline_obj (Pipeline object) – The instance of the Pipeline class that needs to be used for determining the plausibility of the proposed starting positions.

Other Parameters:

emul_i (int or None. Default: None) – If int, number indicating the requested emulator iteration. If None, the last iteration of the emulator will be used.
init_walkers (2D array_like, dict, int or None. Default: None) – Sample set of proposed initial MCMC walker positions. All plausible samples in init_walkers will be returned. If int, generate an LHD of provided size and return all plausible samples. If None, return impl_sam corresponding to iteration emul_i instead.
req_n_walkers (int or None. Default: None) – The minimum required number of plausible starting positions that should be returned. If None, all plausible starting positions in init_walkers are returned instead.

New in version 1.2.0.
unit_space (bool. Default: False) – Bool determining whether or not the provided samples and returned walkers are given in unit space.
lnpost_fn (function or None. Default: None) – If function, call get_hybrid_lnpost_fn() using lnpost_fn and the same values for pipeline_obj, emul_i and unit_space, and return the resulting function definition hybrid_lnpost(). Any additionally provided kwargs are also passed to it.

Returns:

n_walkers (int) – Number of returned MCMC walkers. Note that this number can be higher than req_n_walkers if not None.
p0_walkers (2D ndarray object or dict) – Array containing plausible starting positions of valid MCMC walkers. If init_walkers was provided as a dict, p0_walkers will be a dict.
hybrid_lnpost (function (if lnpost_fn is a function)) – The function returned by get_hybrid_lnpost_fn() using lnpost_fn, pipeline_obj, emul_i, unit_space and kwargs as the input values.