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Integrate univariate solver in polysat

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This commit is contained in:
Jakob Rath 2022-03-18 15:43:06 +01:00
parent 9d47d7959d
commit 509a007ed7
9 changed files with 192 additions and 50 deletions
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79
src/math/polysat/solver.cpp
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@ -31,6 +31,7 @@ namespace polysat {
solver::solver(reslimit& lim):
m_lim(lim),
m_viable(*this),
m_viable_fallback(*this),
m_linear_solver(*this),
m_conflict(*this),
m_simplify(*this),
@ -105,7 +106,8 @@ namespace polysat {
pvar v = m_value.size();
m_value.push_back(rational::zero());
m_justification.push_back(justification::unassigned());
m_viable.push(sz);
m_viable.push_var(sz);
m_viable_fallback.push_var(sz);
m_pwatch.push_back({});
m_activity.push_back(0);
m_vars.push_back(sz2pdd(sz).mk_var(v));
@ -122,7 +124,8 @@ namespace polysat {
void solver::del_var() {
// TODO also remove v from all learned constraints.
pvar v = m_value.size() - 1;
m_viable.pop();
m_viable.pop_var();
m_viable_fallback.pop_var();
m_value.pop_back();
m_justification.pop_back();
m_pwatch.pop_back();
@ -267,7 +270,7 @@ namespace polysat {
auto& wlist = m_pwatch[v];
unsigned i = 0, j = 0, sz = wlist.size();
for (; i < sz && !is_conflict(); ++i)
if (!wlist[i].propagate(*this, v))
if (propagate(v, wlist[i]))
wlist[j++] = wlist[i];
for (; i < sz; ++i)
wlist[j++] = wlist[i];
@ -275,6 +278,32 @@ namespace polysat {
DEBUG_CODE(m_locked_wlist = std::nullopt;);
}
bool solver::propagate(pvar v, signed_constraint c) {
LOG_H3("Propagate " << m_vars[v] << " in " << c);
SASSERT(!c->vars().empty());
unsigned idx = 0;
if (c->var(idx) != v)
idx = 1;
SASSERT(v == c->var(idx));
// find other watch variable.
for (unsigned i = c->vars().size(); i-- > 2; ) {
unsigned other_v = c->vars()[i];
if (!is_assigned(other_v)) {
add_watch(c, other_v);
std::swap(c->vars()[idx], c->vars()[i]);
SASSERT(!is_assigned(c->var(0)));
SASSERT(!is_assigned(c->var(1)));
return true;
}
}
// at most one variable remains unassigned.
unsigned other_v = c->var(idx);
if (!is_assigned(other_v))
m_viable_fallback.push_constraint(other_v, c);
c.narrow(*this, false);
return false;
}
bool solver::propagate(sat::literal lit, clause& cl) {
SASSERT(cl.size() >= 2);
unsigned idx = cl[0] == ~lit ? 1 : 0;
@ -361,6 +390,10 @@ namespace polysat {
m_viable.push_viable();
break;
}
case trail_instr_t::viable_constraint_i: {
m_viable_fallback.pop_constraint();
break;
}
case trail_instr_t::assign_i: {
auto v = m_search.back().var();
LOG_V("Undo assign_i: v" << v);
@ -451,6 +484,7 @@ namespace polysat {
LOG("Decide v" << v);
IF_LOGGING(m_viable.log(v));
rational val;
justification j;
switch (m_viable.find_viable(v, val)) {
case dd::find_t::empty:
// NOTE: all such cases should be discovered elsewhere (e.g., during propagation/narrowing)
@ -458,16 +492,40 @@ namespace polysat {
DEBUG_CODE( UNREACHABLE(); );
m_free_pvars.unassign_var_eh(v);
set_conflict(v);
break;
return;
case dd::find_t::singleton:
// NOTE: this case may happen legitimately if all other possibilities were excluded by brute force search
assign_core(v, val, justification::propagation(m_level));
j = justification::propagation(m_level);
break;
case dd::find_t::multiple:
push_level();
assign_core(v, val, justification::decision(m_level));
j = justification::decision(m_level + 1);
break;
}
}
// Verify the value we're trying to assign
// TODO: we should add a better way to test constraints under assignments, without modifying the solver state.
m_value[v] = val;
m_search.push_assignment(v, val);
bool is_valid = m_viable_fallback.check_constraints(v);
m_search.pop();
if (!is_valid) {
// Try to find a valid replacement value
switch (m_viable_fallback.find_viable(v, val)) {
case dd::find_t::singleton:
case dd::find_t::multiple:
// NOTE: I don't think this can happen if viable::find_viable returned a singleton. since all values excluded by viable are true negatives.
SASSERT(!j.is_propagation());
j = justification::decision(m_level + 1);
break;
case dd::find_t::empty:
m_free_pvars.unassign_var_eh(v);
// TODO: get unsat core from univariate solver
set_conflict(v);
return;
}
}
if (j.is_decision())
push_level();
assign_core(v, val, j);
}
void solver::bdecide(sat::bool_var b) {
@ -484,11 +542,14 @@ namespace polysat {
++m_stats.m_num_propagations;
LOG(assignment_pp(*this, v, val) << " by " << j);
SASSERT(m_viable.is_viable(v, val));
SASSERT(j.level() == m_level);
SASSERT(!is_assigned(v));
SASSERT(std::all_of(assignment().begin(), assignment().end(), [v](auto p) { return p.first != v; }));
m_value[v] = val;
m_search.push_assignment(v, val);
m_trail.push_back(trail_instr_t::assign_i);
m_justification[v] = j;
SASSERT(m_viable_fallback.check_constraints(v));
#if ENABLE_LINEAR_SOLVER
// TODO: convert justification into a format that can be tracked in a depdendency core.
m_linear_solver.set_value(v, val, UINT_MAX);
@ -818,6 +879,8 @@ namespace polysat {
SASSERT(!c->is_active());
c->set_active(true);
add_watch(c);
if (c->vars().size() == 1)
m_viable_fallback.push_constraint(c->var(0), c);
c.narrow(*this, true);
#if ENABLE_LINEAR_SOLVER
m_linear_solver.activate_constraint(c);