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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/tactic/goal2sat.cpp
View file

@ -75,7 +75,6 @@ struct goal2sat::imp : public sat::sat_internalizer {
func_decl_ref_vector m_unhandled_funs;
bool m_default_external;
bool m_euf { false };
bool m_drat { false };
bool m_is_redundant { false };
bool m_top_level { false };
sat::literal_vector aig_lits;
@ -102,7 +101,6 @@ struct goal2sat::imp : public sat::sat_internalizer {
m_ite_extra = p.get_bool("ite_extra", true);
m_max_memory = megabytes_to_bytes(p.get_uint("max_memory", UINT_MAX));
m_euf = sp.euf();
m_drat = sp.drat_file().is_non_empty_string();
}
void throw_op_not_handled(std::string const& s) {
@ -169,15 +167,9 @@ struct goal2sat::imp : public sat::sat_internalizer {
if (m_expr2var_replay && m_expr2var_replay->find(n, v))
return v;
v = m_solver.add_var(is_ext);
log_def(v, n);
return v;
}
void log_def(sat::bool_var v, expr* n) {
if (m_drat && m_euf)
ensure_euf()->drat_bool_def(v, n);
}
sat::bool_var to_bool_var(expr* e) override {
sat::literal l;
sat::bool_var v = m_map.to_bool_var(e);