Summary:
An invariant of `And` and `Or` formulas is that they are flattened,
that is, `And` formulas do not have positive immediate subformulas of
form `And` nor negative immediate subformulas of form `Or`, and
similarly for `Or`. This invariant is ensured by the formula
constructors, which scan the immediate subformulas for cases that need
to be flattened.
When mapping over formulas, this repeated scanning is a performance
bottleneck. Most of the work of flattening is wasted since the input
formulas are necessarily already in flattened form, and the common
case is that the transformation preserves the flattened form. This
diff optimizes this case by detecting violations of flattening during
the transformation, performing the needed flattening, and avoiding the
general constructor that scans for flattening violations.
Reviewed By: jvillard
Differential Revision: D26338014
fbshipit-source-id: 9f15cca58
Summary:
This diff replaces Fml.fold_dnf, which eagerly enumerates a
disjunctive-normal form expansion, with iter_dnf which can be iterated
lazily. Fml.iter_dnf is then used in Context.dnf. This means that the
full DNF expansion does not need to be allocated by
e.g. Smtlib.check_sat, which yields huge peak memory savings.
Reviewed By: jvillard
Differential Revision: D25946111
fbshipit-source-id: e6d179e9f
Summary:
No functional change, only simplifiying and making easier to
generalize.
Reviewed By: jvillard
Differential Revision: D24886572
fbshipit-source-id: e487b815d
Josh Berdine