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experimental feature to access congruence closure of SimpleSolver

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 commit is contained in:
Nikolaj Bjorner 2022-12-30 21:41:27 -08:00
parent c0f1f33898
commit f6d411d54b
21 changed files with 145 additions and 12 deletions

View file

@ -903,6 +903,26 @@ extern "C" {
Z3_CATCH_RETURN(nullptr);
}
Z3_ast Z3_API Z3_solver_congruence_root(Z3_context c, Z3_solver s, Z3_ast a) {
Z3_TRY;
LOG_Z3_solver_congruence_root(c, s, a);
RESET_ERROR_CODE();
init_solver(c, s);
expr* r = to_solver_ref(s)->congruence_root(to_expr(a));
RETURN_Z3(of_expr(r));
Z3_CATCH_RETURN(nullptr);
}
Z3_ast Z3_API Z3_solver_congruence_next(Z3_context c, Z3_solver s, Z3_ast a) {
Z3_TRY;
LOG_Z3_solver_congruence_next(c, s, a);
RESET_ERROR_CODE();
init_solver(c, s);
expr* sib = to_solver_ref(s)->congruence_next(to_expr(a));
RETURN_Z3(of_expr(sib));
Z3_CATCH_RETURN(nullptr);
}
class api_context_obj : public user_propagator::context_obj {
api::context* c;
public:

View file

@ -7241,6 +7241,22 @@ class Solver(Z3PPObject):
cube are likely more useful to cube on."""
return self.cube_vs
def root(self, t):
t = _py2expr(t, self.ctx)
"""Retrieve congruence closure root of the term t relative to the current search state
The function primarily works for SimpleSolver. Terms and variables that are
eliminated during pre-processing are not visible to the congruence closure.
"""
return _to_expr_ref(Z3_solver_congruence_root(self.ctx.ref(), self.solver, t.ast), self.ctx)
def next(self, t):
t = _py2expr(t, self.ctx)
"""Retrieve congruence closure sibling of the term t relative to the current search state
The function primarily works for SimpleSolver. Terms and variables that are
eliminated during pre-processing are not visible to the congruence closure.
"""
return _to_expr_ref(Z3_solver_congruence_next(self.ctx.ref(), self.solver, t.ast), self.ctx)
def proof(self):
"""Return a proof for the last `check()`. Proof construction must be enabled."""
return _to_expr_ref(Z3_solver_get_proof(self.ctx.ref(), self.solver), self.ctx)

View file

@ -6882,6 +6882,26 @@ extern "C" {
*/
void Z3_API Z3_solver_get_levels(Z3_context c, Z3_solver s, Z3_ast_vector literals, unsigned sz, unsigned levels[]);
/**
\brief retrieve the congruence closure root of an expression.
The root is retrieved relative to the state where the solver was in when it completed.
If it completed during a set of case splits, the congruence roots are relative to these case splits.
That is, the congruences are not consequences but they are true under the current state.
def_API('Z3_solver_congruence_root', AST, (_in(CONTEXT), _in(SOLVER), _in(AST)))
*/
Z3_ast Z3_API Z3_solver_congruence_root(Z3_context c, Z3_solver s, Z3_ast a);
/**
\brief retrieve the next expression in the congruence class. The set of congruent siblings form a cyclic list.
Repeated calls on the siblings will result in returning to the original expression.
def_API('Z3_solver_congruence_next', AST, (_in(CONTEXT), _in(SOLVER), _in(AST)))
*/
Z3_ast Z3_API Z3_solver_congruence_next(Z3_context c, Z3_solver s, Z3_ast a);
/**
\brief register a callback to that retrieves assumed, inferred and deleted clauses during search.

View file

@ -81,7 +81,7 @@ public:
*
*/
bool operator()(func_decl* f, unsigned num, expr* const* args, expr_ref& r, expr_ref& side_cond) override {
bool operator()(func_decl* f, unsigned num, expr* const* args, expr_ref& r, proof_ref& pr) override {
SASSERT(f->get_family_id() == m.get_basic_family_id());
switch (f->get_decl_kind()) {
case OP_ITE:
@ -233,7 +233,7 @@ public:
}
bool operator()(func_decl* f, unsigned num, expr* const* args, expr_ref& r, expr_ref& side_cond) override {
bool operator()(func_decl* f, unsigned num, expr* const* args, expr_ref& r, proof_ref& pr) override {
SASSERT(f->get_family_id() == a.get_family_id());
switch (f->get_decl_kind()) {
case OP_ADD:
@ -531,7 +531,7 @@ class bv_expr_inverter : public iexpr_inverter {
* y := 0
*
*/
bool operator()(func_decl* f, unsigned num, expr* const* args, expr_ref& r, expr_ref& side_cond) override {
bool operator()(func_decl* f, unsigned num, expr* const* args, expr_ref& r, proof_ref& pr) override {
SASSERT(f->get_family_id() == bv.get_family_id());
switch (f->get_decl_kind()) {
case OP_BADD:
@ -611,7 +611,7 @@ public:
family_id get_fid() const override { return a.get_family_id(); }
bool operator()(func_decl* f, unsigned num, expr* const* args, expr_ref& r, expr_ref& side_cond) override {
bool operator()(func_decl* f, unsigned num, expr* const* args, expr_ref& r, proof_ref& pr) override {
SASSERT(f->get_family_id() == a.get_family_id());
switch (f->get_decl_kind()) {
case OP_SELECT:
@ -679,7 +679,7 @@ public:
* head(x) -> fresh
* x := cons(fresh, arb)
*/
bool operator()(func_decl* f, unsigned num, expr* const* args, expr_ref& r, expr_ref& side_cond) override {
bool operator()(func_decl* f, unsigned num, expr* const* args, expr_ref& r, proof_ref& pr) override {
if (dt.is_accessor(f)) {
SASSERT(num == 1);
if (uncnstr(args[0])) {
@ -799,7 +799,7 @@ expr_inverter::expr_inverter(ast_manager& m): iexpr_inverter(m) {
}
bool expr_inverter::operator()(func_decl* f, unsigned num, expr* const* args, expr_ref& new_expr, expr_ref& side_cond) {
bool expr_inverter::operator()(func_decl* f, unsigned num, expr* const* args, expr_ref& new_expr, proof_ref& pr) {
if (num == 0)
return false;
@ -812,7 +812,7 @@ bool expr_inverter::operator()(func_decl* f, unsigned num, expr* const* args, ex
return false;
auto* p = m_inverters.get(fid, nullptr);
return p && (*p)(f, num, args, new_expr, side_cond);
return p && (*p)(f, num, args, new_expr, pr);
}
bool expr_inverter::mk_diff(expr* t, expr_ref& r) {
@ -849,3 +849,10 @@ void expr_inverter::set_model_converter(generic_model_converter* mc) {
if (p)
p->set_model_converter(mc);
}
void expr_inverter::set_produce_proofs(bool pr) {
m_produce_proofs = pr;
for (auto* p : m_inverters)
if (p)
p->set_produce_proofs(pr);
}

View file

@ -24,6 +24,7 @@ protected:
ast_manager& m;
std::function<bool(expr*)> m_is_var;
generic_model_converter_ref m_mc;
bool m_produce_proofs = false;
bool uncnstr(expr* e) const { return m_is_var(e); }
bool uncnstr(unsigned num, expr * const * args) const;
@ -37,8 +38,9 @@ public:
virtual ~iexpr_inverter() {}
virtual void set_is_var(std::function<bool(expr*)>& is_var) { m_is_var = is_var; }
virtual void set_model_converter(generic_model_converter* mc) { m_mc = mc; }
virtual void set_produce_proofs(bool p) { m_produce_proofs = true; }
virtual bool operator()(func_decl* f, unsigned n, expr* const* args, expr_ref& new_expr, expr_ref& side_cond) = 0;
virtual bool operator()(func_decl* f, unsigned n, expr* const* args, expr_ref& new_expr, proof_ref& pr) = 0;
virtual bool mk_diff(expr* t, expr_ref& r) = 0;
virtual family_id get_fid() const = 0;
};
@ -49,9 +51,10 @@ class expr_inverter : public iexpr_inverter {
public:
expr_inverter(ast_manager& m);
~expr_inverter() override;
bool operator()(func_decl* f, unsigned n, expr* const* args, expr_ref& new_expr, expr_ref& side_cond) override;
bool operator()(func_decl* f, unsigned n, expr* const* args, expr_ref& new_expr, proof_ref& pr) override;
bool mk_diff(expr* t, expr_ref& r) override;
void set_is_var(std::function<bool(expr*)>& is_var) override;
void set_model_converter(generic_model_converter* mc) override;
void set_produce_proofs(bool p) override;
family_id get_fid() const override { return null_family_id; }
};

View file

@ -62,7 +62,8 @@ bool elim_unconstrained::is_var_lt(int v1, int v2) const {
void elim_unconstrained::eliminate() {
while (!m_heap.empty()) {
expr_ref r(m), side_cond(m);
expr_ref r(m);
proof_ref pr(m);
int v = m_heap.erase_min();
node& n = get_node(v);
if (n.m_refcount == 0)
@ -84,7 +85,7 @@ void elim_unconstrained::eliminate() {
unsigned sz = m_args.size();
for (expr* arg : *to_app(t))
m_args.push_back(reconstruct_term(get_node(arg)));
bool inverted = m_inverter(t->get_decl(), to_app(t)->get_num_args(), m_args.data() + sz, r, side_cond);
bool inverted = m_inverter(t->get_decl(), to_app(t)->get_num_args(), m_args.data() + sz, r, pr);
n.m_refcount = 0;
m_args.shrink(sz);
if (!inverted) {
@ -113,7 +114,7 @@ void elim_unconstrained::eliminate() {
IF_VERBOSE(11, verbose_stream() << mk_bounded_pp(get_node(v).m_orig, m) << " " << mk_bounded_pp(t, m) << " -> " << r << " " << get_node(e).m_refcount << "\n";);
SASSERT(!side_cond && "not implemented to add side conditions\n");
SASSERT(!pr && "not implemented to add proofs\n");
}
}

View file

@ -122,6 +122,8 @@ public:
void set_phase(phase* p) override { m_solver.set_phase(p); }
void move_to_front(expr* e) override { m_solver.move_to_front(e); }
expr_ref_vector cube(expr_ref_vector&, unsigned) override { return expr_ref_vector(m); }
expr* congruence_root(expr* e) override { return e; }
expr* congruence_next(expr* e) override { return e; }
void get_levels(ptr_vector<expr> const& vars, unsigned_vector& depth) override { m_solver.get_levels(vars, depth); }
expr_ref_vector get_trail(unsigned max_level) override { return m_solver.get_trail(max_level); }

View file

@ -110,6 +110,8 @@ namespace opt {
void get_levels(ptr_vector<expr> const& vars, unsigned_vector& depth) override;
expr_ref_vector get_trail(unsigned max_level) override { return m_context.get_trail(max_level); }
expr_ref_vector cube(expr_ref_vector&, unsigned) override { return expr_ref_vector(m); }
expr* congruence_root(expr* e) override { return e; }
expr* congruence_next(expr* e) override { return e; }
void set_phase(expr* e) override { m_context.set_phase(e); }
phase* get_phase() override { return m_context.get_phase(); }
void set_phase(phase* p) override { m_context.set_phase(p); }

View file

@ -463,6 +463,10 @@ public:
}
return fmls;
}
expr* congruence_next(expr* e) override { return e; }
expr* congruence_root(expr* e) override { return e; }
lbool get_consequences_core(expr_ref_vector const& assumptions, expr_ref_vector const& vars, expr_ref_vector& conseq) override {
init_preprocess();

View file

@ -476,6 +476,9 @@ public:
set_reason_unknown(m_solver.get_reason_unknown());
return fmls;
}
expr* congruence_next(expr* e) override { return e; }
expr* congruence_root(expr* e) override { return e; }
lbool find_mutexes(expr_ref_vector const& vars, vector<expr_ref_vector>& mutexes) override {

View file

@ -213,6 +213,20 @@ namespace smt {
return out;
}
expr* kernel::congruence_root(expr * e) {
smt::enode* n = m_imp->m_kernel.find_enode(e);
if (!n)
return e;
return n->get_root()->get_expr();
}
expr* kernel::congruence_next(expr * e) {
smt::enode* n = m_imp->m_kernel.find_enode(e);
if (!n)
return e;
return n->get_next()->get_expr();
}
void kernel::collect_statistics(::statistics & st) const {
m_imp->m_kernel.collect_statistics(st);
}

View file

@ -239,6 +239,13 @@ namespace smt {
*/
expr_ref_vector cubes(unsigned depth);
/**
\brief access congruence closure
*/
expr* congruence_next(expr* e);
expr* congruence_root(expr* e);
/**
\brief retrieve depth of variables from decision stack.

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@ -330,6 +330,10 @@ namespace {
m_context.get_units(units);
}
expr* congruence_next(expr* e) override { return m_context.congruence_next(e); }
expr* congruence_root(expr* e) override { return m_context.congruence_root(e); }
expr_ref_vector cube(expr_ref_vector& vars, unsigned cutoff) override {
ast_manager& m = get_manager();
if (!m_cuber) {

View file

@ -275,6 +275,10 @@ public:
return m_solver2->cube(vars, backtrack_level);
}
expr* congruence_next(expr* e) override { switch_inc_mode(); return m_solver2->congruence_next(e); }
expr* congruence_root(expr* e) override { switch_inc_mode(); return m_solver2->congruence_root(e); }
expr * get_assumption(unsigned idx) const override {
unsigned c1 = m_solver1->get_num_assumptions();
if (idx < c1) return m_solver1->get_assumption(idx);

View file

@ -238,6 +238,15 @@ public:
virtual expr_ref_vector cube(expr_ref_vector& vars, unsigned backtrack_level) = 0;
/**
\brief retrieve congruence closure root.
*/
virtual expr* congruence_root(expr* e) = 0;
/**
\brief retrieve congruence closure sibling
*/
virtual expr* congruence_next(expr* e) = 0;
/**
\brief Display the content of this solver.

View file

@ -262,6 +262,9 @@ public:
expr_ref_vector cube(expr_ref_vector& vars, unsigned ) override { return expr_ref_vector(m); }
expr* congruence_next(expr* e) override { return e; }
expr* congruence_root(expr* e) override { return e; }
ast_manager& get_manager() const override { return m_base->get_manager(); }
void refresh(solver* new_base) {

View file

@ -136,6 +136,9 @@ public:
return expr_ref_vector(get_manager());
}
expr* congruence_next(expr* e) override { return e; }
expr* congruence_root(expr* e) override { return e; }
model_converter_ref get_model_converter() const override { return m_mc; }
void get_levels(ptr_vector<expr> const& vars, unsigned_vector& depth) override {

View file

@ -210,6 +210,8 @@ public:
void set_reason_unknown(char const* msg) override { m_solver->set_reason_unknown(msg); }
void get_labels(svector<symbol> & r) override { m_solver->get_labels(r); }
ast_manager& get_manager() const override { return m; }
expr* congruence_next(expr* e) override { return m_solver->congruence_next(e); }
expr* congruence_root(expr* e) override { return m_solver->congruence_root(e); }
expr_ref_vector cube(expr_ref_vector& vars, unsigned backtrack_level) override { flush_assertions(); return m_solver->cube(vars, backtrack_level); }
lbool find_mutexes(expr_ref_vector const& vars, vector<expr_ref_vector>& mutexes) override { return m_solver->find_mutexes(vars, mutexes); }
lbool get_consequences_core(expr_ref_vector const& asms, expr_ref_vector const& vars, expr_ref_vector& consequences) override {

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@ -131,6 +131,9 @@ public:
expr_ref_vector cube(expr_ref_vector& vars, unsigned backtrack_level) override {
return m_solver->cube(vars, backtrack_level);
}
expr* congruence_next(expr* e) override { return m_solver->congruence_next(e); }
expr* congruence_root(expr* e) override { return m_solver->congruence_root(e); }
lbool get_consequences_core(expr_ref_vector const& asms, expr_ref_vector const& vars, expr_ref_vector& consequences) override {
datatype_util dt(m);

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@ -122,6 +122,8 @@ public:
void get_labels(svector<symbol> & r) override { m_solver->get_labels(r); }
ast_manager& get_manager() const override { return m; }
expr_ref_vector cube(expr_ref_vector& vars, unsigned backtrack_level) override { flush_assertions(); return m_solver->cube(vars, backtrack_level); }
expr* congruence_next(expr* e) override { return m_solver->congruence_next(e); }
expr* congruence_root(expr* e) override { return m_solver->congruence_root(e); }
lbool find_mutexes(expr_ref_vector const& vars, vector<expr_ref_vector>& mutexes) override { return m_solver->find_mutexes(vars, mutexes); }
lbool get_consequences_core(expr_ref_vector const& asms, expr_ref_vector const& vars, expr_ref_vector& consequences) override {
flush_assertions();

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@ -2086,6 +2086,10 @@ namespace smtfd {
expr_ref_vector cube(expr_ref_vector& vars, unsigned backtrack_level) override {
return expr_ref_vector(m);
}
expr* congruence_root(expr* e) override { return e; }
expr* congruence_next(expr* e) override { return e; }
lbool get_consequences_core(expr_ref_vector const& asms, expr_ref_vector const& vars, expr_ref_vector& consequences) override {
return l_undef;