- scan_for_linear returns true if it finds a new linear equation. It then should break GB.
- if scan_for_linear returns false, it should still allow try_modify_eqs.
This behavior was masked by requiring scan_for_linear to always be true before
allowing try_to_modify_eqs.
based on repro from Guido Martinez @mtzguido
deals with fluke regression for F* reported by Guido Martinez
Background:
The automatic pattern inference facility looks for terms that contains all bound variables of a quantifier. It may end up with a term that contains all bound variables but the extracted term can be simplified.
Example. The pattern
(ApplyTT (ApplyTT @x3!1 (ApplyTT @x4!0 (:var 1))) (ApplyTT @x4!0 (:var 0)))
can be decomposed into a multi-pattern
(ApplyTT @x4!0 (:var 1))) (ApplyTT @x4!0 (:var 0))
The multi-pattern may enable a quantifier instantiation while the original pattern does not. The multi-pattern should be preferred.
The regression showed up based on a change that should not be considered harmful but turned out to be noticeable.
The change was a simplification of and-or expressions based on sorting. This played with the case split queue used by F* (smt.case_split = 3) that uses a top-level case split of clauses to avoid redundant branches. The net effect was that without sorting, the benchmarks would always choose the opportune branch that enabled matching against the larger term. With sorting it would mostly choose inopportune branches.
- add option pp.no_lets (default = false) to print formulas without let (used by the low-level SMT2 printer).
- print lemmas2console faster by using the low level printer
- add check for lambdas similar to as-array in context of quantifiers. MBQI is not a decision procedure for this combination and can then incorrectly conclude satisfiabiltiy.
Scenario
The formula contains assertions
- bv = (map or (lambda ..) t)
- forall y (not (select bv (pair s y)))
Since bv is extensionally equal to a term that depends on a lambda, MBQI cannot just take the current finite approximation of bv when checking the quantifier for satisfiability.
this update enables new incremental linear axioms based on division terms.
It also consolidates some of the backtracking state in nla_core / emons to use stack traces instead of custom backtracking state.
- 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.
-
- 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))
```
