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overhaul of proof format for new solver

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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 commit is contained in:
Nikolaj Bjorner 2022-08-28 17:44:33 -07:00
parent 9922c766b9
commit e2f4fc2307
37 changed files with 809 additions and 1078 deletions
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8
src/sat/sat_config.cpp
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@ -197,10 +197,10 @@ namespace sat {
m_drat_check_unsat = p.drat_check_unsat();
m_drat_check_sat = p.drat_check_sat();
m_drat_file = p.drat_file();
m_drat = !p.drat_disable() && (sp.lemmas2console() || m_drat_check_unsat || m_drat_file.is_non_empty_string() || m_drat_check_sat) && p.threads() == 1;
m_smt_proof = p.smt_proof();
m_drat = !p.drat_disable() && (sp.lemmas2console() || m_drat_check_unsat || m_drat_file.is_non_empty_string() || m_smt_proof.is_non_empty_string() || m_drat_check_sat) && p.threads() == 1;
m_drat_binary = p.drat_binary();
m_drat_activity = p.drat_activity();
m_drup_trim = p.drup_trim();
m_dyn_sub_res = p.dyn_sub_res();
// Parameters used in Liang, Ganesh, Poupart, Czarnecki AAAI 2016.
@ -254,10 +254,6 @@ namespace sat {
sat_simplifier_params ssp(_p);
m_elim_vars = ssp.elim_vars();
#if 0
if (m_drat && (m_xor_solver || m_card_solver))
throw sat_param_exception("DRAT checking only works for pure CNF");
#endif
}
void config::collect_param_descrs(param_descrs & r) {