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add bound refinement propagation

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2020-08-12 10:10:31 -07:00
parent 7fc4653e47
commit be3c3dacb3
4 changed files with 74 additions and 30 deletions
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2
src/smt/params/smt_params_helper.pyg
View file

@ -64,7 +64,7 @@ def_module_params(module_name='smt',
('arith.nl.gr_q', UINT, 10, 'grobner\'s quota'),
('arith.nl.grobner_subs_fixed', UINT, 2, '0 - no subs, 1 - substitute, 2 - substitute fixed zeros only'),
('arith.propagate_eqs', BOOL, True, 'propagate (cheap) equalities'),
('arith.propagation_mode', UINT, 2, '0 - no propagation, 1 - propagate existing literals, 2 - refine bounds'),
('arith.propagation_mode', UINT, 1, '0 - no propagation, 1 - propagate existing literals, 2 - refine finite bounds'),
('arith.reflect', BOOL, True, 'reflect arithmetical operators to the congruence closure'),
('arith.branch_cut_ratio', UINT, 2, 'branch/cut ratio for linear integer arithmetic'),
('arith.int_eq_branch', BOOL, False, 'branching using derived integer equations'),

2
src/smt/params/theory_arith_params.h
View file

@ -34,7 +34,7 @@ enum arith_solver_id {
enum bound_prop_mode {
BP_NONE,
BP_SIMPLE, // only used for implying literals
BP_REFINE // refine known bounds
BP_REFINE // adds new literals, but only refines finite bounds
};
enum arith_prop_strategy {

6
src/smt/smt_parallel.cpp
View file

@ -95,7 +95,11 @@ namespace smt {
auto cube = [](context& ctx, expr_ref_vector& lasms, expr_ref& c) {
lookahead lh(ctx);
c = lh.choose();
if (c) lasms.push_back(c);
if (c) {
if ((ctx.get_random_value() % 2) == 0)
c = c.get_manager().mk_not(c);
lasms.push_back(c);
}
};
obj_hashtable<expr> unit_set;

94
src/smt/theory_lra.cpp
View file

@ -680,6 +680,13 @@ class theory_lra::imp {
return th.is_attached_to_var(e);
}
void ensure_bounds(theory_var v) {
while (m_bounds.size() <= static_cast<unsigned>(v)) {
m_bounds.push_back(lp_bounds());
m_unassigned_bounds.push_back(0);
}
}
theory_var mk_var(expr* n) {
if (!ctx().e_internalized(n)) {
ctx().internalize(n, false);
@ -690,10 +697,7 @@ class theory_lra::imp {
v = th.mk_var(e);
TRACE("arith", tout << "fresh var: v" << v << " " << mk_pp(n, m) << "\n";);
SASSERT(m_bounds.size() <= static_cast<unsigned>(v) || m_bounds[v].empty());
if (m_bounds.size() <= static_cast<unsigned>(v)) {
m_bounds.push_back(lp_bounds());
m_unassigned_bounds.push_back(0);
}
ensure_bounds(v);
ctx().attach_th_var(e, &th, v);
}
else {
@ -2296,19 +2300,13 @@ public:
}
bool should_propagate() {
bool should_propagate() const {
return BP_NONE != propagation_mode();
}
// void update_propagation_threshold(bool made_progress) {
// if (made_progress) {
// m_propagation_delay = std::max(1u, m_propagation_delay-1u);
// }
// else {
// m_propagation_delay += 2;
// }
// }
bool should_refine_bounds() const {
return BP_REFINE == propagation_mode() && ctx().at_search_level();
}
void consume(rational const& v, lp::constraint_index j) {
set_evidence(j, m_core, m_eqs);
@ -2323,9 +2321,8 @@ public:
m_bp.init();
lp().propagate_bounds_for_touched_rows(m_bp);
if (!m.inc()) {
if (!m.inc())
return;
}
if (is_infeasible()) {
get_infeasibility_explanation_and_set_conflict();
@ -2342,12 +2339,15 @@ public:
bool bound_is_interesting(unsigned vi, lp::lconstraint_kind kind, const rational & bval) const {
theory_var v = lp().local_to_external(vi);
if (v == null_theory_var) {
if (v == null_theory_var)
return false;
}
if (m_bounds.size() <= static_cast<unsigned>(v) || m_unassigned_bounds[v] == 0) {
if (should_refine_bounds())
return true;
if (m_bounds.size() <= static_cast<unsigned>(v) || m_unassigned_bounds[v] == 0)
return false;
}
for (lp_api::bound* b : m_bounds[v]) {
if (ctx().get_assignment(b->get_bv()) == l_undef &&
null_literal != is_bound_implied(kind, bval, *b)) {
@ -2360,13 +2360,14 @@ public:
lpvar vi = be.m_j;
theory_var v = lp().local_to_external(vi);
if (v == null_theory_var) return;
TRACE("arith", tout << "v" << v << " " << be.kind() << " " << be.m_bound << "\n";
// if (m_unassigned_bounds[v] == 0) lp().print_bound_evidence(be, tout);
);
if (v == null_theory_var)
return;
TRACE("arith", tout << "v" << v << " " << be.kind() << " " << be.m_bound << "\n";);
ensure_bounds(v);
if (m_unassigned_bounds[v] == 0 || m_bounds.size() <= static_cast<unsigned>(v)) {
if (m_unassigned_bounds[v] == 0 && !should_refine_bounds()) {
TRACE("arith", tout << "return\n";);
return;
}
@ -2405,9 +2406,48 @@ public:
VERIFY(ctx().get_assignment(lit) == l_true);
});
++m_stats.m_bound_propagations1;
assign(lit, m_core, m_eqs, m_params);
assign(lit, m_core, m_eqs, m_params);
}
if (should_refine_bounds() && first)
refine_bound(v, be);
}
void refine_bound(theory_var v, const lp::implied_bound& be) {
lpvar vi = be.m_j;
if (lp::tv::is_term(vi))
return;
expr_ref w(get_enode(v)->get_owner(), m);
if (a.is_add(w) || a.is_numeral(w) || m.is_ite(w))
return;
literal bound = null_literal;
switch (be.kind()) {
case lp::LE:
if (is_int(v) && (lp().column_has_lower_bound(vi) || !lp().column_has_upper_bound(vi)))
bound = mk_literal(a.mk_le(w, a.mk_numeral(floor(be.m_bound), a.is_int(w))));
if (is_real(v) && !lp().column_has_upper_bound(vi))
bound = mk_literal(a.mk_le(w, a.mk_numeral(be.m_bound, a.is_int(w))));
break;
case lp::GE:
if (is_int(v) && (lp().column_has_upper_bound(vi) || !lp().column_has_lower_bound(vi)))
bound = mk_literal(a.mk_ge(w, a.mk_numeral(ceil(be.m_bound), a.is_int(w))));
if (is_real(v) && !lp().column_has_lower_bound(vi))
bound = mk_literal(a.mk_ge(w, a.mk_numeral(be.m_bound, a.is_int(w))));
break;
default:
break;
}
if (bound == null_literal)
return;
if (ctx().get_assignment(bound) == l_true)
return;
++m_stats.m_bound_propagations1;
reset_evidence();
m_explanation.clear();
lp().explain_implied_bound(be, m_bp);
ctx().mark_as_relevant(bound);
assign(bound, m_core, m_eqs, m_params);
}
void add_eq(lpvar u, lpvar v, lp::explanation const& e) {