def _initialize_global_variables(likelihood, priors, search_parameter_keys,
    use_ratio):
    """
    Store a global copy of the likelihood, priors, and search keys for
    multiprocessing.
    """
    global _likelihood
    global _priors
    global _search_parameter_keys
    global _use_ratio
    _likelihood = likelihood
    _priors = priors
    _search_parameter_keys = search_parameter_keys
    _use_ratio = use_ratio
