The parametric engine works under the assumption that models
are well-defined, i.e., that parameter valuations will lead
to graph-preserving probabilities, etc.
If we encounter a point in a region where these assumptions
don't hold, we now treat this by splitting the region. Regions
with such an improper midpoint that are below the precision
threshold are considered to be undefined and further processing
is aborted.
In particular, this treatment ensures that we never perform
policy iteration on a model with parameter instantiation
that is not well defined / supported. E.g., if there
were negative rewards for such a point, policy iteration
would previously not necessarily terminate.
Joachim Klein
2207684335