EUF proofs are checked modulo union-find.
Equalities are added to to union-find if they are assumptions or if they can be derived using congruence closure. The congruence closure assumptions are added as proof-hints.
Note that this proof format does not track equality inferences, symmetry and transitivity. Instead they are handled by assuming a union-find based checker.
#6319 - fix incompleteness in propagation of default to all array terms in the equivalence class.
Fix bug with q_mbi where domain restrictions are not using values because the current model does not evaluate certain bound variables to values. Set model completion when adding these bound variables to the model to ensure their values are not missed.
Add better propagation of diagnostics when tactics and the new solver return unknown. The reason for unknown can now be traced to what theory was culprit (currently no additional information)
using a queue for disequality propagaiton was a regression: values of numerals can change along the same stack so prior passing the filter does not mean it passes later.
literals that are replayed need to be registered with respective theories, otherwise, they will not propagate with the theories (the enode have to be attached with relevant theory variables).
delay propagation on each disequality/equality should suffice once. It adds relevant inequalities to ensure the arithmetic solver is coherent about disequalities.
This commit overhauls the proof format (in development) for the new core.
NOTE: this functionality is work in progress with a long way to go.
It is shielded by the sat.euf option, which is off by default and in pre-release state.
It is too early to fuzz or use it. It is pushed into master to shed light on road-map for certifying inferences of sat.euf.
It retires the ad-hoc extension of DRUP used by the SAT solver.
Instead it relies on SMT with ad-hoc extensions for proof terms.
It adds the following commands (consumed by proof_cmds.cpp):
- assume - for input clauses
- learn - when a clause is learned (or redundant clause is added)
- del - when a clause is deleted.
The commands take a list of expressions of type Bool and the
last argument can optionally be of type Proof.
When the last argument is of type Proof it is provided as a hint
to justify the learned clause.
Proof hints can be checked using a self-contained proof
checker. The sat/smt/euf_proof_checker.h class provides
a plugin dispatcher for checkers.
It is instantiated with a checker for arithmetic lemmas,
so far for Farkas proofs.
Use example:
```
(set-option :sat.euf true)
(set-option :tactic.default_tactic smt)
(set-option :sat.smt.proof f.proof)
(declare-const x Int)
(declare-const y Int)
(declare-const z Int)
(declare-const u Int)
(assert (< x y))
(assert (< y z))
(assert (< z x))
(check-sat)
```
Run z3 on a file with above content.
Then run z3 on f.proof
```
(verified-smt)
(verified-smt)
(verified-smt)
(verified-farkas)
(verified-smt)
```
this update addresses some perf regressions introduced when handling axioms for bv2int and a memory smash regression when decoupling bv-ackerman from in-processing. It adds a filter based on bv_eq_axioms for disabling ackerman reductions on disequalities.
previous scheme has Ackmerman module instrument main solver to backjump and simplify when reaching a threshold.
This destroys overall performance: simplification does many more things than invoking Ackerman axioms.
Having a dependency between simplification (in-processing) and depleting a priority queue of auxiliary axioms therefore hurts overall performance. It has to be decoupled. The current approach is now to empty the axiom queue on occasion.
It is still not ideal - it should be coupled with the search level - axioms don't survive higher levels where redundant clauses get garbage collected as they don't have a chance of being used.
