Dynamically set precision values

[hyanwong]

At the moment we are setting the precision value to a default of 14. In some testing of the precision parameter, I dynamically set the precision to be the smallest negative exponent of the non-zero mismatch or recombination probabilities, plus 3, as below.

            nonzero_probs = np.concatenate(
                (recombination[recombination > 0], mismatch[mismatch > 0])
            )
            # TODO Is this a good default? Need to investigate the effects.
            if len(nonzero_probs) > 0:
                precision = 3 + int(np.ceil(-np.log10(np.min(nonzero_probs))))
            else:
                precision = 5  # Needs testing

However, this might need testing / revising anyway when Hartigan parsimony is implemented in https://github.com/tskit-dev/tsinfer/issues/374

[jeromekelleher]

Good idea - let's get it in for 0.2.1