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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2021-07-02 11:26:05 -07:00
parent 0520180846
commit 0fc9d7ad0d
4 changed files with 256 additions and 183 deletions

View file

@ -48,12 +48,23 @@ public:
mod_interval(Numeral const& l, Numeral const& h): lo(l), hi(h) {}
static mod_interval free() { return mod_interval(0, 0); }
static mod_interval empty() { mod_interval i(0, 0); i.emp = true; return i; }
bool is_free() const { return !emp && lo == hi; }
bool is_empty() const { return emp; }
bool is_singleton() const { return !is_empty() && (lo + 1 == hi || (hi == 0 && is_max(lo))); }
bool contains(Numeral const& n) const;
virtual bool is_max(Numeral const& n) const { return n + 1 == 0; }
void set_free() { lo = hi = 0; emp = false; }
void set_bounds(Numeral const& l, Numeral const& h) { lo = l; hi = h; }
void set_empty() { emp = true; }
bool contains(Numeral const& n) const;
void intersect_ule(Numeral const& h);
void intersect_uge(Numeral const& l);
void intersect_ult(Numeral const& h);
void intersect_ugt(Numeral const& l);
void intersect_fixed(Numeral const& n);
void intersect_diff(Numeral const& n);
mod_interval operator&(mod_interval const& other) const;
mod_interval operator+(mod_interval const& other) const;
mod_interval operator-(mod_interval const& other) const;

View file

@ -120,3 +120,89 @@ Numeral mod_interval<Numeral>::closest_value(Numeral const& n) const {
return lo;
return hi - 1;
}
// TBD: correctness and completeness for wrap-around semantics needs to be checked/fixed
template<typename Numeral>
void mod_interval<Numeral>::intersect_ule(Numeral const& h) {
if (is_empty())
return;
if (is_max(h))
return;
else if (is_free())
lo = 0, hi = h + 1;
else if (hi > lo && lo > h)
set_empty();
else if (hi != 0 || h + 1 < hi)
hi = h + 1;
}
template<typename Numeral>
void mod_interval<Numeral>::intersect_uge(Numeral const& l) {
if (is_empty())
return;
if (lo < hi && hi <= l)
set_empty();
else if (is_free())
lo = l, hi = 0;
else if (lo < hi && lo < l)
lo = l;
}
template<typename Numeral>
void mod_interval<Numeral>::intersect_ult(Numeral const& h) {
if (is_empty())
return;
if (h == 0)
set_empty();
else if (is_free())
lo = 0, hi = h;
else if (hi > lo && lo >= h)
set_empty();
else if (hi > lo && h < hi)
hi = h;
}
template<typename Numeral>
void mod_interval<Numeral>::intersect_ugt(Numeral const& l) {
if (is_empty())
return;
if (is_max(l))
set_empty();
else if (is_free())
lo = l + 1, hi = 0;
else if (lo > l)
return;
else if (lo < hi && hi <= l)
set_empty();
else if (lo < hi)
lo = l + 1;
}
template<typename Numeral>
void mod_interval<Numeral>::intersect_fixed(Numeral const& a) {
if (is_empty())
return;
if (!contains(a))
set_empty();
else if (is_max(a))
lo = a, hi = 0;
else
lo = a, hi = a + 1;
}
template<typename Numeral>
void mod_interval<Numeral>::intersect_diff(Numeral const& a) {
if (!contains(a) || is_empty())
return;
if (a == lo && a + 1 == hi)
set_empty();
else if (a == lo && hi == 0 && is_max(a))
set_empty();
else if (a == lo && !is_max(a))
lo = a + 1;
else if (a + 1 == hi)
hi = a;
else if (hi == 0 && is_max(a))
hi = a;
}

View file

@ -44,139 +44,78 @@ namespace polysat {
return a + 1 == rational::power_of_two(m_num_bits);
}
bool viable_set::is_singleton() const {
return !is_empty() && (lo + 1 == hi || (hi == 0 && is_max(lo)));
}
void viable_set::intersect_eq(rational const& a, bool is_positive) {
if (is_empty())
return;
if (is_positive) {
if (!contains(a))
set_empty();
else if (is_max(a))
lo = a, hi = 0;
else
lo = a, hi = a + 1;
}
else {
if (!contains(a))
return;
if (a == lo && a + 1 == hi)
set_empty();
else if (a == lo && hi == 0 && is_max(a))
set_empty();
else if (a == lo && !is_max(a))
lo = a + 1;
else if (a + 1 == hi)
hi = a;
else if (hi == 0 && is_max(a))
hi = a;
else
std::cout << "unhandled diseq " << lo << " " << a << " " << hi << "\n";
}
if (is_positive)
intersect_fixed(a);
else
intersect_diff(a);
}
bool viable_set::intersect_eq(rational const& a, rational const& b, bool is_positive) {
if (a.is_odd()) {
if (b == 0)
intersect_eq(b, is_positive);
else {
rational a_inv;
VERIFY(a.mult_inverse(m_num_bits, a_inv));
intersect_eq(mod(a_inv * -b, p2()), is_positive);
}
return true;
if (!a.is_odd()) {
std::function<bool(rational const&)> eval = [&](rational const& x) {
return is_positive == (mod(a * x + b, p2()) == 0);
};
return narrow(eval);
}
if (b == 0)
intersect_eq(b, is_positive);
else {
return false;
rational a_inv;
VERIFY(a.mult_inverse(m_num_bits, a_inv));
intersect_eq(mod(a_inv * -b, p2()), is_positive);
}
return true;
}
void viable_set::intersect_eq(rational const& a, rational const& b, bool is_positive, unsigned& budget) {
std::function<bool(rational const&)> eval = [&](rational const& x) {
return is_positive == (mod(a * x + b, p2()) == 0);
};
narrow(eval, budget);
}
bool viable_set::intersect_ule(rational const& a, rational const& b, rational const& c, rational const& d, bool is_positive) {
bool viable_set::intersect_le(rational const& a, rational const& b, rational const& c, rational const& d, bool is_positive) {
// x <= 0
if (a.is_odd() && b == 0 && c == 0 && d == 0)
intersect_eq(b, is_positive);
else if (a == 1 && b == 0 && c == 0) {
// x <= d
// x <= d or x > d
if (is_positive)
set_hi(d);
// x > d
else if (is_max(d))
set_empty();
else
set_lo(d + 1);
intersect_ule(d);
else
intersect_ugt(d);
}
else if (a == 0 && c == 1 && d == 0) {
// x >= b
// x >= b or x < b
if (is_positive)
set_lo(b);
else if (b == 0)
set_empty();
intersect_uge(b);
else
set_hi(b - 1);
intersect_ult(b);
}
// TBD: can also handle wrap-around semantics (for signed comparison)
else {
std::function<bool(rational const&)> eval = [&](rational const& x) {
return is_positive == mod(a * x + b, p2()) <= mod(c * x + d, p2());
};
return narrow(eval);
}
else
return false;
return true;
}
void viable_set::narrow(std::function<bool(rational const&)>& eval, unsigned& budget) {
while (budget > 0 && !eval(lo) && !is_max(lo) && !is_empty()) {
rational viable_set::prev(rational const& p) const {
if (p > 0)
return p - 1;
else
return rational::power_of_two(m_num_bits) - 1;
}
bool viable_set::narrow(std::function<bool(rational const&)>& eval) {
unsigned budget = 10;
while (budget > 0 && !is_empty() && !eval(lo)) {
--budget;
lo += 1;
set_lo(lo);
intersect_diff(lo);
}
while (budget > 0 && hi > 0 && !eval(hi - 1) && !is_empty()) {
while (budget > 0 && !is_empty() && !eval(prev(hi))) {
--budget;
hi = hi - 1;
set_hi(hi);
intersect_diff(prev(hi));
}
return 0 < budget;
}
void viable_set::intersect_ule(rational const& a, rational const& b, rational const& c, rational const& d, bool is_positive, unsigned& budget) {
std::function<bool(rational const&)> eval = [&](rational const& x) {
return is_positive == mod(a * x + b, p2()) <= mod(c * x + d, p2());
};
narrow(eval, budget);
}
void viable_set::set_hi(rational const& d) {
if (is_max(d))
return;
else if (is_free())
lo = 0, hi = d + 1;
else if (lo > d)
set_empty();
else if (hi != 0 || d + 1 < hi)
hi = d + 1;
else if (d + 1 == hi)
return;
else
std::cout << "set hi " << d << " " << *this << "\n";
}
void viable_set::set_lo(rational const& b) {
if (hi != 0 && hi <= b)
set_empty();
else if (is_free())
lo = b, hi = 0;
else if (lo < b)
lo = b;
else if (lo == b)
return;
else
std::cout << "set lo " << b << " " << *this << "\n";
}
#endif
viable::viable(solver& s):
@ -184,6 +123,18 @@ namespace polysat {
m_bdd(1000)
{}
viable::~viable() {
#if NEW_VIABLE
ptr_vector<cached_constraint> entries;
for (auto* e : m_constraint_cache)
entries.push_back(e);
m_constraint_cache.reset();
for (auto* e : entries)
dealloc(e);
#endif
}
void viable::push_viable(pvar v) {
s.m_trail.push_back(trail_instr_t::viable_i);
m_viable_trail.push_back(std::make_pair(v, m_viable[v]));
@ -200,15 +151,8 @@ namespace polysat {
void viable::intersect_eq(rational const& a, pvar v, rational const& b, bool is_positive) {
#if NEW_VIABLE
push_viable(v);
if (!m_viable[v].intersect_eq(a, b, is_positive)) {
IF_VERBOSE(10, verbose_stream() << "could not intersect v" << v << " " << m_viable[v] << "\n");
unsigned budget = 10;
m_viable[v].intersect_eq(a, b, is_positive, budget);
if (budget == 0) {
std::cout << "budget used\n";
// then narrow the range using BDDs
}
}
if (!m_viable[v].intersect_eq(a, b, is_positive))
intersect_eq_bdd(v, a, b, is_positive);
if (m_viable[v].is_empty())
s.set_conflict(v);
#else
@ -239,54 +183,9 @@ namespace polysat {
void viable::intersect_ule(pvar v, rational const& a, rational const& b, rational const& c, rational const& d, bool is_positive) {
#if NEW_VIABLE
//
// TODO This code needs to be partitioned into self-contained pieces.
//
push_viable(v);
if (!m_viable[v].intersect_ule(a, b, c, d, is_positive)) {
unsigned budget = 10;
m_viable[v].intersect_ule(a, b, c, d, is_positive, budget);
if (budget == 0) {
std::cout << "miss: " << a << " " << b << " " << c << " " << d << " " << is_positive << "\n";
unsigned sz = var2bits(v).num_bits();
bdd le = m_bdd.mk_true();
ineq_entry entry0(sz, a, b, c, d, le);
ineq_entry* other = nullptr;
if (!m_ineq_cache.find(&entry0, other)) {
std::cout << "ADD-to-cache\n";
bddv const& x = var2bits(v).var();
le = ((a * x) + b) <= ((c * x) + d);
other = alloc(ineq_entry, sz, a, b, c, d, le);
m_ineq_cache.insert(other);
}
bdd gt = is_positive ? !other->repr : other->repr;
other->m_activity++;
//
// instead of using activity for GC, use the Move-To-Front approach
// see sat/smt/bv_ackerman.h or sat/smt/euf_ackerman.h
// where hash table entries use a dll_base.
//
// le(lo) is false: find min x >= lo, such that le(x) is false, le(x+1) is true
// le(hi) is false: find max x =< hi, such that le(x) is false, le(x-1) is true
rational bound = m_viable[v].lo;
if (var2bits(v).sup(gt, bound)) {
m_viable[v].set_lo(bound);
m_viable[v].set_ne(bound);
}
bound = m_viable[v].hi;
if (bound != 0) {
bound = bound - 1;
if (var2bits(v).inf(gt, bound)) {
std::cout << "TODO: new upper bound " << bound << "\n";
}
}
}
}
if (!m_viable[v].intersect_le(a, b, c, d, is_positive))
intersect_ule_bdd(v, a, b, c, d, is_positive);
if (m_viable[v].is_empty())
s.set_conflict(v);
#else
@ -305,6 +204,77 @@ namespace polysat {
#endif
}
#if NEW_VIABLE
viable::cached_constraint& viable::cache_constraint(pvar v, cached_constraint& entry0, std::function<bdd(void)>& mk_constraint) {
cached_constraint* other = nullptr;
if (!m_constraint_cache.find(&entry0, other)) {
gc_cached_constraints();
other = alloc(cached_constraint, entry0);
other->repr = mk_constraint();
m_constraint_cache.insert(other);
}
other->m_activity++;
return *other;
}
void viable::gc_cached_constraints() {
//
// TODO: instead of using activity for GC, use the Move-To-Front approach
// see sat/smt/bv_ackerman.h or sat/smt/euf_ackerman.h
// where hash table entries use a dll_base.
//
unsigned max_entries = 10000;
if (m_constraint_cache.size() > max_entries) {
ptr_vector<cached_constraint> entries;
for (auto* e : m_constraint_cache)
entries.push_back(e);
std::stable_sort(entries.begin(), entries.end(), [&](cached_constraint* a, cached_constraint* b) { return a->m_activity < b->m_activity; });
for (unsigned i = 0; i < max_entries/2; ++i) {
m_constraint_cache.remove(entries[i]);
dealloc(entries[i]);
}
}
}
void viable::narrow(pvar v, bdd const& is_false) {
rational bound = m_viable[v].lo;
if (var2bits(v).sup(is_false, bound))
m_viable[v].intersect_ugt(bound);
bound = m_viable[v].prev(m_viable[v].hi);
if (var2bits(v).inf(is_false, bound))
m_viable[v].intersect_ult(bound);
}
void viable::intersect_ule_bdd(pvar v, rational const& a, rational const& b, rational const& c, rational const& d, bool is_positive) {
unsigned sz = var2bits(v).num_bits();
std::function<bdd(void)> le = [&]() {
bddv const& x = var2bits(v).var();
return ((a * x) + b) <= ((c * x) + d);
};
cached_constraint entry0(sz, a, b, c, d, m_bdd.mk_true());
cached_constraint& entry = cache_constraint(v, entry0, le);
// le(lo) is false: find min x >= lo, such that le(x) is false, le(x+1) is true
// le(hi) is false: find max x =< hi, such that le(x) is false, le(x-1) is true
bdd gt = is_positive ? !entry.repr : entry.repr;
narrow(v, gt);
}
void viable::intersect_eq_bdd(pvar v, rational const& a, rational const& b, bool is_positive) {
unsigned sz = var2bits(v).num_bits();
std::function<bdd(void)> eq = [&]() {
bddv const& x = var2bits(v).var();
return ((a * x) + b) == rational(0);
};
cached_constraint entry0(sz, a, b, m_bdd.mk_true());
cached_constraint& entry = cache_constraint(v, entry0, eq);
bdd ne = is_positive ? !entry.repr : entry.repr;
narrow(v, ne);
}
#endif
bool viable::has_viable(pvar v) {
#if NEW_VIABLE
return !m_viable[v].is_empty();
@ -325,7 +295,7 @@ namespace polysat {
#if NEW_VIABLE
push_viable(v);
IF_VERBOSE(10, verbose_stream() << " v" << v << " != " << val << "\n");
m_viable[v].set_ne(val);
m_viable[v].intersect_diff(val);
if (m_viable[v].is_empty())
s.set_conflict(v);
#else

View file

@ -14,12 +14,11 @@ Author:
Notes:
NEW_VIABLE uses cheaper book-keeping, but is partial.
The implementation of NEW_VIABLE is atm incomplete and ad-hoc.
--*/
#pragma once
#define NEW_VIABLE 0
#define NEW_VIABLE 1
#include <limits>
@ -44,52 +43,57 @@ namespace polysat {
class viable_set : public mod_interval<rational> {
unsigned m_num_bits;
rational p2() const { return rational::power_of_two(m_num_bits); }
bool is_max(rational const& a) const;
bool is_max(rational const& a) const override;
void intersect_eq(rational const& a, bool is_positive);
void narrow(std::function<bool(rational const&)>& eval, unsigned& budget);
bool narrow(std::function<bool(rational const&)>& eval);
public:
viable_set(unsigned num_bits): m_num_bits(num_bits) {}
bool is_singleton() const;
dd::find_t find_hint(rational const& c, rational& val) const;
void set_ne(rational const& a) { intersect_eq(a, false); }
void set_lo(rational const& lo);
void set_hi(rational const& hi);
bool intersect_eq(rational const& a, rational const& b, bool is_positive);
void intersect_eq(rational const& a, rational const& b, bool is_positive, unsigned& budget);
bool intersect_ule(rational const& a, rational const& b, rational const& c, rational const& d, bool is_positive);
void intersect_ule(rational const& a, rational const& b, rational const& c, rational const& d, bool is_positive, unsigned& budget);
bool intersect_le(rational const& a, rational const& b, rational const& c, rational const& d, bool is_positive);
rational prev(rational const& p) const;
};
#endif
class viable {
solver& s;
typedef dd::bdd bdd;
typedef dd::fdd fdd;
solver& s;
dd::bdd_manager m_bdd;
scoped_ptr_vector<dd::fdd> m_bits;
#if NEW_VIABLE
struct ineq_entry {
struct cached_constraint {
enum op_code { is_ule, is_eq };
op_code m_op;
unsigned m_num_bits;
rational a, b, c, d;
bdd repr;
unsigned m_activity = 0;
ineq_entry(unsigned n, rational const& a, rational const& b, rational const& c, rational const& d, bdd& f) :
m_num_bits(n), a(a), b(b), c(c), d(d), repr(f) {}
cached_constraint(unsigned n, rational const& a, rational const& b, rational const& c, rational const& d, bdd& f) :
m_op(op_code::is_ule), m_num_bits(n), a(a), b(b), c(c), d(d), repr(f) {}
cached_constraint(unsigned n, rational const& a, rational const& b, bdd& f) :
m_op(op_code::is_eq), m_num_bits(n), a(a), b(b), repr(f) {}
struct hash {
unsigned operator()(ineq_entry const* e) const {
return mk_mix(e->a.hash(), e->b.hash(), mk_mix(e->c.hash(), e->d.hash(), e->m_num_bits));
unsigned operator()(cached_constraint const* e) const {
return mk_mix(e->a.hash(), e->b.hash(), mk_mix(e->c.hash(), e->d.hash(), e->m_num_bits)) + e->m_op;
}
};
struct eq {
bool operator()(ineq_entry const* x, ineq_entry const* y) const {
return x->a == y->a && x->b == y->b && x->c == y->c && x->d == y->d && x->m_num_bits == y->m_num_bits;
bool operator()(cached_constraint const* x, cached_constraint const* y) const {
return x->m_op == y->m_op && x->a == y->a && x->b == y->b && x->c == y->c && x->d == y->d && x->m_num_bits == y->m_num_bits;
}
};
};
vector<viable_set> m_viable;
vector<std::pair<pvar, viable_set>> m_viable_trail;
hashtable<ineq_entry*, ineq_entry::hash, ineq_entry::eq> m_ineq_cache;
hashtable<cached_constraint*, cached_constraint::hash, cached_constraint::eq> m_constraint_cache;
void intersect_ule_bdd(pvar v, rational const& a, rational const& b, rational const& c, rational const& d, bool is_positive);
void intersect_eq_bdd(pvar v, rational const& a, rational const& b, bool is_positive);
cached_constraint& cache_constraint(pvar v, cached_constraint& entry0, std::function<bdd(void)>& mk_constraint);
void gc_cached_constraints();
void narrow(pvar v, bdd const& is_false);
#else
@ -110,6 +114,8 @@ namespace polysat {
public:
viable(solver& s);
~viable();
void push(unsigned num_bits) {
#if NEW_VIABLE
m_viable.push_back(viable_set(num_bits));