Utilities¶

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

prism.utils.get_lnpost_fn(ext_lnpost, pipeline_obj, emul_i=None, unit_space=True, hybrid=True)[source]¶

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

This get_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 the ext_lnpost function if it is plausible.

This function needs to be called by all MPI ranks.

Other Parameters:
Parameters:	ext_lnpost (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 `ext_lnpost(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: True) – Bool determining whether or not the provided sample will be given in unit space. hybrid (bool. Default: True) – Bool determining whether or not the get_lnpost function should use the implausibility values of a given par_set as an additional prior.
Returns:	get_lnpost (function) – Definition of the function `get_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.

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 get_lnpost is called.

prism.utils.get_walkers(pipeline_obj, emul_i=None, init_walkers=None, unit_space=True, ext_lnpost=None, **kwargs)[source]¶

Analyzes proposed init_walkers and returns valid 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 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 validity of the proposed walkers.

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, 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.
unit_space (bool. Default: True) – Bool determining whether or not the provided samples and returned walkers are given in unit space.
ext_lnpost (function or None. Default: None) – If function, call get_lnpost_fn() function factory using ext_lnpost and the same values for pipeline_obj, emul_i and unit_space, and return the resulting function definition get_lnpost. Any additionally provided kwargs are also passed to it.

Returns:

n_walkers (int) – Number of returned MCMC walkers.
p0_walkers (2D ndarray object) – Array containing starting positions of valid MCMC walkers.
get_lnpost (function (if ext_lnpost is a function)) – The function returned by get_lnpost_fn() function factory using ext_lnpost, pipeline_obj, emul_i, unit_space and kwargs as the input values.