Add the ability to customize incremental pre-processing simplification for the SMTLIB2 front-end. The main new capability is to use pre-processing tactics in incremental mode that were previously not available. The main new capabilities are
- solve-eqs
- reduce-args
- elim-unconstrained
There are several more. Documentation and exposed simplifiers are populated incrementally. The current set of supported simplifiers can be inspected by using z3 with the --simplifiers flag or referring to https://microsoft.github.io/z3guide/docs/strategies/simplifiers
Some pending features are:
- add the ability to update parameters to simplifiers similar to how tactics can be controlled using parameters.
- expose simplification solvers over the binary API.
move sat_smt_preprocess to solver
fix bugs in model_reconstruction_trail for dependency replay
This is a preparatory step for exposing pre-processing as tactics.
- convert reduce-args to a simplifier. Currently exposed as reduce-args2 tactic until the old tactic code gets removed.
- bug fixes in model_reconstruction trail
- allow multiple defs to be added with same pool of removed formulas
- fix tracking of function symbols instead of expressions to filter replay
- add nla_divisions to track (cheap) divisibility lemmas.
-
leverage interval propagation for bounds.
merge functionality with propagate-ineqs tactic
remove the new propagate-bounds tactic and instead use propagate-ineqs
- increase build version to 4.12.1. This prepares updated release for MacOs-11 build on x86
- move literal propagation mode in euf-egraph to a callback and traversal of equivalence class. Track antecedent by newest equality instead of root. This makes equality propagation to literals have similar behavior as in legacy solver and appears to result in a speedup (10% fewer conflicts on QF_UF/QG-classification/qg5/iso_icl478.smt2 in preliminary testing)
- fix interaction of pre-processing and assumptions. Pre-processing has to freeze assumption literals so they don't get eliminated. This is similar to dependencies that are already frozen.
This update includes an experimental feature to access a congruence closure data-structure after search.
It comes with several caveats as pre-processing is free to eliminate terms. It is therefore necessary to use a solver that does not eliminate the terms you want to track for congruence of. This is partially addressed by using SimpleSolver or incremental mode solving.
```python
from z3 import *
s = SimpleSolver()
x, y, z = Ints('x y z')
s.add(x == y)
s.add(y == z)
s.check()
print(s.root(x), s.root(y), s.root(z))
print(s.next(x), s.next(y), s.next(z))
```
This would crash before:
(declare-fun x () (_ BitVec 4))
(assert (not (bvule x #x1)))
(apply elim-uncnstr2)
That's because the index_set iterator was querying qtail to compute the end of the iteration
But the problem is that elim-uncnstr2 may add new fmls to the goal, as in this case.
The bvule is replaced with an 'or', but since it's negated, it turns into 2 goals
Solve the issue by freezing the qtail for the iteration loop.
This is the right behavior for elim-uncnstr2, as it can't rewrite exprs that haven't been analyzed before
@NikolajBjorner please check if this the right behavior for the other simplifiers. Thank you
