Random State¶

When performing reproducibility/variability experiments, it is important to isolate sources of variability. One such source is random state.

Users can fix the random state of C-PAC’s execution by specifying a random seed. When adding a Node that should accept a user-specified random seed, add

the nipype.interfaces.base.core.Interface and the corresponding flags to add/remove to set the random seed, or
in the case of a CPAC.utils.interfaces.function.Function Node, the Function node’s function and a function to apply to that function definition to set the random seed

to CPAC.pipeline.random_state.seed.random_seed_flags.

CPAC.pipeline.random_state.seed.random_seed_flags()[source]¶

Function to return dictionary of flags with current random seed.

Parameters:

None

Returns:

dict of {‘functions’: {function: function}, ‘interfaces’: {list or tuple}}

Developer note: sequence matters here! Only the first match will be applied!

In the ‘functions’ sub-dictionary, each key should be a function used in a CPAC.utils.interfaces.function.Function, and each value should be a function that takes a single parameter (a function) to apply to the key-function such that, once the value-function is applied, the random seed is applied when the key-function is run.

In the ‘interfaces’ sub-dictionary, each key should be an nipype.interfaces.base.core.Interface, and each value should be either a list of strings to add to the interface’s flags/args or a tuple of (list of strings to add to, list of strings to remove from) the interface’s flags/args.

Examples

>>> list(random_seed_flags().keys())
['functions', 'interfaces']
>>> all([isinstance(random_seed_flags()[key], dict) for key in [
...     'functions', 'interfaces']])
True
>>> rs = set_up_random_state('random')
>>> list(random_seed_flags().keys())
['functions', 'interfaces']
>>> all([isinstance(random_seed_flags()[key], dict) for key in [
...     'functions', 'interfaces']])
True