z3-z3-4.13.0.src.sat.smt.recfun_solver.cpp Maven / Gradle / Ivy
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/*++
Copyright (c) 2020 Microsoft Corporation
Module Name:
recfun_solver.cpp
Abstract:
Recursive function solver plugin
Author:
Nikolaj Bjorner (nbjorner) 2021-02-09
--*/
#include "ast/rewriter/var_subst.h"
#include "sat/smt/recfun_solver.h"
#include "sat/smt/euf_solver.h"
#define TRACEFN(x) TRACE("recfun", tout << x << '\n';)
namespace recfun {
solver::solver(euf::solver& ctx):
th_euf_solver(ctx, symbol("recfun"), ctx.get_manager().mk_family_id("recfun")),
m_plugin(*reinterpret_cast(m.get_plugin(ctx.get_manager().mk_family_id("recfun")))),
m_util(m_plugin.u()),
m_disabled_guards(m),
m_enabled_guards(m),
m_preds(m) {
}
solver::~solver() {
reset();
}
void solver::reset() {
m_stats.reset();
m_disabled_guards.reset();
m_enabled_guards.reset();
m_propagation_queue.reset();
for (auto & kv : m_guard2pending)
dealloc(kv.m_value);
m_guard2pending.reset();
}
expr_ref solver::apply_args(vars const & vars, expr_ref_vector const & args, expr * e) {
SASSERT(is_standard_order(vars));
var_subst subst(m, true);
expr_ref new_body = subst(e, args);
ctx.get_rewriter()(new_body);
return new_body;
}
/**
* For functions f(args) that are given as macros f(vs) = rhs
*
* 1. substitute `e.args` for `vs` into the macro rhs
* 2. add unit clause `f(args) = rhs`
*/
void solver::assert_macro_axiom(case_expansion & e) {
m_stats.m_macro_expansions++;
TRACEFN("case expansion " << e);
SASSERT(e.m_def->is_fun_macro());
auto & vars = e.m_def->get_vars();
app_ref lhs = e.m_lhs;
expr_ref rhs = apply_args(vars, e.m_args, e.m_def->get_rhs());
unsigned generation = std::max(ctx.get_max_generation(lhs), ctx.get_max_generation(rhs));
euf::solver::scoped_generation _sgen(ctx, generation + 1);
auto eq = eq_internalize(lhs, rhs);
add_unit(eq);
}
/**
* Add case axioms for every case expansion path.
*
* assert `p(args) <=> And(guards)` (with CNF on the fly)
*
* also body-expand paths that do not depend on any defined fun
*/
void solver::assert_case_axioms(case_expansion & e) {
if (e.m_def->is_fun_macro()) {
assert_macro_axiom(e);
return;
}
++m_stats.m_case_expansions;
TRACEFN("assert_case_axioms " << e
<< " with " << e.m_def->get_cases().size() << " cases");
SASSERT(e.m_def->is_fun_defined());
// add case-axioms for all case-paths
// assert this was not defined before.
sat::literal_vector preds;
auto & vars = e.m_def->get_vars();
for (case_def const & c : e.m_def->get_cases()) {
// applied predicate to `args`
app_ref pred_applied = c.apply_case_predicate(e.m_args);
SASSERT(u().owns_app(pred_applied));
preds.push_back(mk_literal(pred_applied));
expr_ref_vector guards(m);
for (auto & g : c.get_guards())
guards.push_back(apply_args(vars, e.m_args, g));
if (c.is_immediate()) {
body_expansion be(pred_applied, c, e.m_args);
assert_body_axiom(be);
}
else if (!is_enabled_guard(pred_applied)) {
disable_guard(pred_applied, guards);
continue;
}
assert_guard(pred_applied, guards);
}
add_clause(preds);
}
void solver::assert_guard(expr* pred_applied, expr_ref_vector const& guards) {
sat::literal_vector lguards;
for (expr* ga : guards)
lguards.push_back(mk_literal(ga));
add_equiv_and(mk_literal(pred_applied), lguards);
}
void solver::block_core(expr_ref_vector const& core) {
sat::literal_vector clause;
for (expr* e : core)
clause.push_back(~mk_literal(e));
add_clause(clause);
}
/**
* make clause `depth_limit => ~guard`
* the guard appears at a depth below the current cutoff.
*/
void solver::disable_guard(expr* guard, expr_ref_vector const& guards) {
SASSERT(!is_enabled_guard(guard));
app_ref dlimit = m_util.mk_num_rounds_pred(m_num_rounds);
expr_ref_vector core(m);
core.push_back(dlimit);
core.push_back(guard);
if (!m_guard2pending.contains(guard)) {
m_disabled_guards.push_back(guard);
m_guard2pending.insert(guard, alloc(expr_ref_vector, guards));
}
TRACEFN("add clause\n" << core);
push_c(core);
}
/**
* For a guarded definition guards => f(vars) = rhs
* and occurrence f(args)
*
* substitute `args` for `vars` in guards, and rhs
* add axiom guards[args/vars] => f(args) = rhs[args/vars]
*
*/
void solver::assert_body_axiom(body_expansion & e) {
++m_stats.m_body_expansions;
recfun::def & d = *e.m_cdef->get_def();
auto & vars = d.get_vars();
auto & args = e.m_args;
SASSERT(is_standard_order(vars));
sat::literal_vector clause;
for (auto & g : e.m_cdef->get_guards()) {
expr_ref guard = apply_args(vars, args, g);
if (m.is_false(guard))
return;
if (m.is_true(guard))
continue;
clause.push_back(~mk_literal(guard));
}
expr_ref lhs(u().mk_fun_defined(d, args), m);
expr_ref rhs = apply_args(vars, args, e.m_cdef->get_rhs());
clause.push_back(eq_internalize(lhs, rhs));
add_clause(clause);
}
void solver::get_antecedents(sat::literal l, sat::ext_justification_idx idx, sat::literal_vector& r, bool probing) {
UNREACHABLE();
}
void solver::asserted(sat::literal l) {
expr* e = ctx.bool_var2expr(l.var());
if (!l.sign() && u().is_case_pred(e))
push_body_expand(e);
}
sat::check_result solver::check() {
return sat::check_result::CR_DONE;
}
std::ostream& solver::display(std::ostream& out) const {
return out << "disabled guards:\n" << m_disabled_guards << "\n";
}
void solver::collect_statistics(statistics& st) const {
st.update("recfun macro expansion", m_stats.m_macro_expansions);
st.update("recfun case expansion", m_stats.m_case_expansions);
st.update("recfun body expansion", m_stats.m_body_expansions);
}
euf::th_solver* solver::clone(euf::solver& ctx) {
return alloc(solver, ctx);
}
bool solver::unit_propagate() {
force_push();
if (m_qhead == m_propagation_queue.size())
return false;
ctx.push(value_trail(m_qhead));
for (; m_qhead < m_propagation_queue.size() && !s().inconsistent(); ++m_qhead) {
auto& p = *m_propagation_queue[m_qhead];
if (p.is_guard())
assert_guard(p.guard(), *m_guard2pending[p.guard()]);
else if (p.is_core())
block_core(p.core());
else if (p.is_case())
assert_case_axioms(p.case_ex());
else
assert_body_axiom(p.body());
}
return true;
}
void solver::push_prop(propagation_item* p) {
m_propagation_queue.push_back(p);
ctx.push(push_back_vector>(m_propagation_queue));
}
sat::literal solver::internalize(expr* e, bool sign, bool root) {
force_push();
SASSERT(m.is_bool(e));
if (!visit_rec(m, e, sign, root)) {
TRACE("array", tout << mk_pp(e, m) << "\n";);
return sat::null_literal;
}
auto lit = expr2literal(e);
if (sign)
lit.neg();
return lit;
}
void solver::internalize(expr* e) {
force_push();
visit_rec(m, e, false, false);
}
bool solver::visited(expr* e) {
euf::enode* n = expr2enode(e);
return n && n->is_attached_to(get_id());
}
bool solver::visit(expr* e) {
if (visited(e))
return true;
if (!is_app(e) || to_app(e)->get_family_id() != get_id()) {
ctx.internalize(e);
return true;
}
m_stack.push_back(sat::eframe(e));
return false;
}
bool solver::post_visit(expr* e, bool sign, bool root) {
euf::enode* n = expr2enode(e);
SASSERT(!n || !n->is_attached_to(get_id()));
if (!n)
n = mk_enode(e, false);
SASSERT(!n->is_attached_to(get_id()));
euf::theory_var w = mk_var(n);
ctx.attach_th_var(n, this, w);
if (u().is_defined(e) && u().has_defs())
push_case_expand(e);
return true;
}
void solver::add_assumptions(sat::literal_set& assumptions) {
if (u().has_defs() || m_disabled_guards.empty()) {
app_ref dlimit = m_util.mk_num_rounds_pred(m_num_rounds);
TRACEFN("add_theory_assumption " << dlimit);
sat::literal assumption = mk_literal(dlimit);
assumptions.insert(assumption);
s().assign_scoped(assumption);
for (auto g : m_disabled_guards) {
assumption = ~mk_literal(g);
assumptions.insert(assumption);
s().assign_scoped(assumption);
}
}
for (expr* g : m_enabled_guards)
push_guard(g);
}
bool solver::should_research(sat::literal_vector const& core) {
bool found = false;
unsigned min_gen = UINT_MAX;
expr* to_delete = nullptr;
unsigned n = 0;
for (sat::literal lit : core) {
expr* e = ctx.bool_var2expr(lit.var());
if (lit.sign() && is_disabled_guard(e)) {
found = true;
unsigned gen = ctx.get_max_generation(e);
if (gen < min_gen)
n = 0;
if (gen <= min_gen && s().rand()() % (++n) == 0) {
to_delete = e;
min_gen = gen;
}
}
else if (u().is_num_rounds(e))
found = true;
}
if (found) {
++m_num_rounds;
if (!to_delete && !m_disabled_guards.empty())
to_delete = m_disabled_guards.back();
if (to_delete) {
m_disabled_guards.erase(to_delete);
m_enabled_guards.push_back(to_delete);
IF_VERBOSE(2, verbose_stream() << "(smt.recfun :enable-guard " << mk_pp(to_delete, m) << ")\n");
}
else {
IF_VERBOSE(2, verbose_stream() << "(smt.recfun :increment-round)\n");
}
}
return found;
}
bool solver::is_beta_redex(euf::enode* p, euf::enode* n) const {
return is_defined(p) || is_case_pred(p);
}
bool solver::add_dep(euf::enode* n, top_sort& dep) {
if (n->num_args() == 0)
dep.insert(n, nullptr);
for (auto* k : euf::enode_args(n))
dep.add(n, k);
return true;
}
void solver::add_value(euf::enode* n, model& mdl, expr_ref_vector& values) {
values.set(n->get_root_id(), n->get_root()->get_expr());
}
}