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[datalog] fix stratum cycle break for rules with multiple looping dependecies

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e.g.
a -> b
b-> a
a -> a

this change makes the cycle breaker quadratic on the number of predicates. This should be revisited later

Signed-off-by: Nuno Lopes <t-nclaud@microsoft.com>
This commit is contained in:
Nuno Lopes 2013-04-15 16:53:25 -07:00
parent a054b099c1
commit 1f5097cdaa
1 changed files with 10 additions and 11 deletions
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21
src/muz_qe/dl_compiler.cpp
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@ -803,17 +803,15 @@ namespace datalog {
context& m_context; context& m_context;
item_set & m_removed; item_set & m_removed;
svector<T> m_stack; svector<T> m_stack;
ast_mark m_stack_content;
ast_mark m_visited; ast_mark m_visited;
void traverse(T v) { void traverse(T v) {
SASSERT(!m_stack_content.is_marked(v)); SASSERT(!m_visited.is_marked(v));
if(m_visited.is_marked(v) || m_removed.contains(v)) { if (m_removed.contains(v)) {
return; return;
} }
m_stack.push_back(v); m_stack.push_back(v);
m_stack_content.mark(v, true);
m_visited.mark(v, true); m_visited.mark(v, true);
const item_set & deps = m_deps.get_deps(v); const item_set & deps = m_deps.get_deps(v);
@ -821,33 +819,34 @@ namespace datalog {
item_set::iterator end = deps.end(); item_set::iterator end = deps.end();
for(; it!=end; ++it) { for(; it!=end; ++it) {
T d = *it; T d = *it;
if(m_stack_content.is_marked(d)) { if (m_visited.is_marked(d)) {
//TODO: find the best vertex to remove in the cycle //TODO: find the best vertex to remove in the cycle
remove_from_stack(); remove_from_stack();
break; continue;
} }
traverse(d); traverse(d);
} }
SASSERT(m_stack.back()==v); SASSERT(m_stack.back()==v);
m_stack.pop_back(); m_stack.pop_back();
m_stack_content.mark(v, false); m_visited.mark(v, false);
} }
void remove_from_stack() { void remove_from_stack() {
for (unsigned i = 0; i < m_stack.size(); ++i) { for (unsigned i = 0; i < m_stack.size(); ++i) {
func_decl* p = m_stack[i]; func_decl* p = m_stack[i];
rule_vector const& rules = m_rules.get_predicate_rules(p);
unsigned stratum = m_rules.get_predicate_strat(p);
if (m_context.has_facts(p)) { if (m_context.has_facts(p)) {
m_removed.insert(p); m_removed.insert(p);
return; return;
} }
rule_vector const& rules = m_rules.get_predicate_rules(p);
unsigned stratum = m_rules.get_predicate_strat(p);
for (unsigned j = 0; j < rules.size(); ++j) { for (unsigned j = 0; j < rules.size(); ++j) {
rule const& r = *rules[j]; rule const& r = *rules[j];
bool ok = true; bool ok = true;
for (unsigned k = 0; ok && k < r.get_uninterpreted_tail_size(); ++k) { for (unsigned k = 0; ok && k < r.get_uninterpreted_tail_size(); ++k) {
ok &= m_rules.get_predicate_strat(r.get_decl(k)) < stratum; ok = m_rules.get_predicate_strat(r.get_decl(k)) < stratum;
} }
if (ok) { if (ok) {
m_removed.insert(p); m_removed.insert(p);
@ -858,8 +857,8 @@ namespace datalog {
// nothing was found. // nothing was found.
m_removed.insert(m_stack.back()); m_removed.insert(m_stack.back());
} }
public: public:
cycle_breaker(rule_dependencies & deps, rule_set const& rules, context& ctx, item_set & removed) cycle_breaker(rule_dependencies & deps, rule_set const& rules, context& ctx, item_set & removed)
: m_deps(deps), m_rules(rules), m_context(ctx), m_removed(removed) { SASSERT(removed.empty()); } : m_deps(deps), m_rules(rules), m_context(ctx), m_removed(removed) { SASSERT(removed.empty()); }