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Merge pull request #999 from mtrberzi/theory-aware-branching

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Theory-aware branching heuristic
This commit is contained in:
Nikolaj Bjorner 2017-05-02 15:32:37 -07:00 committed by GitHub
parent ed0b2be618 15cb2d7dba
commit 5b0286001b
6 changed files with 163 additions and 6 deletions
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3
src/smt/params/smt_params.h
View file

@ -66,7 +66,8 @@ enum case_split_strategy {
CS_ACTIVITY_WITH_CACHE, // case split based on activity and cache the activity
CS_RELEVANCY, // case split based on relevancy
CS_RELEVANCY_ACTIVITY, // case split based on relevancy and activity
CS_RELEVANCY_GOAL // based on relevancy and the current goal
CS_RELEVANCY_GOAL, // based on relevancy and the current goal
CS_ACTIVITY_THEORY_AWARE_BRANCHING // activity-based case split, but theory solvers can manipulate activity
};
struct smt_params : public preprocessor_params,

2
src/smt/params/smt_params_helper.pyg
View file

@ -11,7 +11,7 @@ def_module_params(module_name='smt',
('phase_selection', UINT, 3, 'phase selection heuristic: 0 - always false, 1 - always true, 2 - phase caching, 3 - phase caching conservative, 4 - phase caching conservative 2, 5 - random, 6 - number of occurrences'),
('restart_strategy', UINT, 1, '0 - geometric, 1 - inner-outer-geometric, 2 - luby, 3 - fixed, 4 - arithmetic'),
('restart_factor', DOUBLE, 1.1, 'when using geometric (or inner-outer-geometric) progression of restarts, it specifies the constant used to multiply the currect restart threshold'),
('case_split', UINT, 1, '0 - case split based on variable activity, 1 - similar to 0, but delay case splits created during the search, 2 - similar to 0, but cache the relevancy, 3 - case split based on relevancy (structural splitting), 4 - case split on relevancy and activity, 5 - case split on relevancy and current goal'),
('case_split', UINT, 1, '0 - case split based on variable activity, 1 - similar to 0, but delay case splits created during the search, 2 - similar to 0, but cache the relevancy, 3 - case split based on relevancy (structural splitting), 4 - case split on relevancy and activity, 5 - case split on relevancy and current goal, 6 - activity-based case split with theory-aware branching activity'),
('delay_units', BOOL, False, 'if true then z3 will not restart when a unit clause is learned'),
('delay_units_threshold', UINT, 32, 'maximum number of learned unit clauses before restarting, ignored if delay_units is false'),
('pull_nested_quantifiers', BOOL, False, 'pull nested quantifiers'),

147
src/smt/smt_case_split_queue.cpp
View file

@ -22,9 +22,13 @@ Revision History:
#include"stopwatch.h"
#include"for_each_expr.h"
#include"ast_pp.h"
#include"map.h"
#include"hashtable.h"
namespace smt {
typedef map<bool_var, double, int_hash, default_eq<bool_var> > theory_var_priority_map;
struct bool_var_act_lt {
svector<double> const & m_activity;
bool_var_act_lt(svector<double> const & a):m_activity(a) {}
@ -35,6 +39,27 @@ namespace smt {
typedef heap<bool_var_act_lt> bool_var_act_queue;
struct theory_aware_act_lt {
svector<double> const & m_activity;
theory_var_priority_map const & m_theory_var_priority;
theory_aware_act_lt(svector<double> const & act, theory_var_priority_map const & a):m_activity(act),m_theory_var_priority(a) {}
bool operator()(bool_var v1, bool_var v2) const {
double p_v1, p_v2;
if (!m_theory_var_priority.find(v1, p_v1)) {
p_v1 = 0.0;
}
if (!m_theory_var_priority.find(v2, p_v2)) {
p_v2 = 0.0;
}
// add clause activity
p_v1 += m_activity[v1];
p_v2 += m_activity[v2];
return p_v1 > p_v2;
}
};
typedef heap<theory_aware_act_lt> theory_aware_act_queue;
/**
\brief Case split queue based on activity and random splits.
*/
@ -1086,16 +1111,130 @@ namespace smt {
m_params.m_qi_eager_threshold += start_gen;
}
};
class theory_aware_branching_queue : public case_split_queue {
protected:
context & m_context;
smt_params & m_params;
theory_var_priority_map m_theory_var_priority;
theory_aware_act_queue m_queue;
int_hashtable<int_hash, default_eq<bool_var> > m_theory_vars;
map<bool_var, lbool, int_hash, default_eq<bool_var> > m_theory_var_phase;
public:
theory_aware_branching_queue(context & ctx, smt_params & p):
m_context(ctx),
m_params(p),
m_theory_var_priority(),
m_queue(1024, theory_aware_act_lt(ctx.get_activity_vector(), m_theory_var_priority)) {
}
virtual void activity_increased_eh(bool_var v) {
if (m_queue.contains(v))
m_queue.decreased(v);
}
virtual void mk_var_eh(bool_var v) {
m_queue.reserve(v+1);
m_queue.insert(v);
}
virtual void del_var_eh(bool_var v) {
if (m_queue.contains(v))
m_queue.erase(v);
}
virtual void unassign_var_eh(bool_var v) {
if (!m_queue.contains(v))
m_queue.insert(v);
}
virtual void relevant_eh(expr * n) {}
virtual void init_search_eh() {}
virtual void end_search_eh() {}
virtual void reset() {
m_queue.reset();
}
virtual void push_scope() {}
virtual void pop_scope(unsigned num_scopes) {}
virtual void next_case_split(bool_var & next, lbool & phase) {
int threshold = static_cast<int>(m_params.m_random_var_freq * random_gen::max_value());
SASSERT(threshold >= 0);
if (m_context.get_random_value() < threshold) {
SASSERT(m_context.get_num_b_internalized() > 0);
next = m_context.get_random_value() % m_context.get_num_b_internalized();
TRACE("random_split", tout << "next: " << next << " get_assignment(next): " << m_context.get_assignment(next) << "\n";);
if (m_context.get_assignment(next) == l_undef)
return;
}
while (!m_queue.empty()) {
next = m_queue.erase_min();
if (m_context.get_assignment(next) == l_undef)
return;
}
next = null_bool_var;
if (m_theory_vars.contains(next)) {
if (!m_theory_var_phase.find(next, phase)) {
phase = l_undef;
}
}
}
virtual void add_theory_aware_branching_info(bool_var v, double priority, lbool phase) {
TRACE("theory_aware_branching", tout << "Add theory-aware branching information for l#" << v << ": priority=" << priority << std::endl;);
m_theory_vars.insert(v);
m_theory_var_phase.insert(v, phase);
m_theory_var_priority.insert(v, priority);
if (m_queue.contains(v)) {
if (priority > 0.0) {
m_queue.decreased(v);
} else {
m_queue.increased(v);
}
}
// m_theory_queue.reserve(v+1);
// m_theory_queue.insert(v);
}
virtual void display(std::ostream & out) {
bool first = true;
bool_var_act_queue::const_iterator it = m_queue.begin();
bool_var_act_queue::const_iterator end = m_queue.end();
for (; it != end ; ++it) {
unsigned v = *it;
if (m_context.get_assignment(v) == l_undef) {
if (first) {
out << "remaining case-splits:\n";
first = false;
}
out << "#" << m_context.bool_var2expr(v)->get_id() << " ";
}
}
if (!first)
out << "\n";
}
virtual ~theory_aware_branching_queue() {};
};
case_split_queue * mk_case_split_queue(context & ctx, smt_params & p) {
if (p.m_relevancy_lvl < 2 && (p.m_case_split_strategy == CS_RELEVANCY || p.m_case_split_strategy == CS_RELEVANCY_ACTIVITY ||
p.m_case_split_strategy == CS_RELEVANCY_GOAL)) {
p.m_case_split_strategy == CS_RELEVANCY_GOAL)) {
warning_msg("relevancy must be enabled to use option CASE_SPLIT=3, 4 or 5");
p.m_case_split_strategy = CS_ACTIVITY;
}
if (p.m_auto_config && (p.m_case_split_strategy == CS_RELEVANCY || p.m_case_split_strategy == CS_RELEVANCY_ACTIVITY ||
p.m_case_split_strategy == CS_RELEVANCY_GOAL)) {
p.m_case_split_strategy == CS_RELEVANCY_GOAL)) {
warning_msg("auto configuration (option AUTO_CONFIG) must be disabled to use option CASE_SPLIT=3, 4 or 5");
p.m_case_split_strategy = CS_ACTIVITY;
}
@ -1110,6 +1249,8 @@ namespace smt {
return alloc(rel_act_case_split_queue, ctx, p);
case CS_RELEVANCY_GOAL:
return alloc(rel_goal_case_split_queue, ctx, p);
case CS_ACTIVITY_THEORY_AWARE_BRANCHING:
return alloc(theory_aware_branching_queue, ctx, p);
default:
return alloc(act_case_split_queue, ctx, p);
}

3
src/smt/smt_case_split_queue.h
View file

@ -46,6 +46,9 @@ namespace smt {
virtual void next_case_split(bool_var & next, lbool & phase) = 0;
virtual void display(std::ostream & out) = 0;
virtual ~case_split_queue() {}
// theory-aware branching hint
virtual void add_theory_aware_branching_info(bool_var v, double priority, lbool phase) {}
};
case_split_queue * mk_case_split_queue(context & ctx, smt_params & p);

4
src/smt/smt_context.cpp
View file

@ -3022,6 +3022,10 @@ namespace smt {
}
}
void context::add_theory_aware_branching_info(bool_var v, double priority, lbool phase) {
m_case_split_queue->add_theory_aware_branching_info(v, priority, phase);
}
bool context::propagate_th_case_split(unsigned qhead) {
if (m_all_th_case_split_literals.empty())
return true;

10
src/smt/smt_context.h
View file

@ -838,12 +838,20 @@ namespace smt {
*/
void mk_th_case_split(unsigned num_lits, literal * lits);
/*
* Provide a hint to the branching heuristic about the priority of a "theory-aware literal".
* Literals marked in this way will always be branched on before unmarked literals,
* starting with the literal having the highest priority.
*/
void add_theory_aware_branching_info(bool_var v, double priority, lbool phase);
public:
// helper function for trail
void undo_th_case_split(literal l);
bool propagate_th_case_split(unsigned qhead);
bool propagate_th_case_split(unsigned qhead);
bool_var mk_bool_var(expr * n);