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working on viable

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Nikolaj Bjorner 2023-12-09 13:10:47 -08:00
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135
src/sat/smt/polysat_core.h
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/*++
Copyright (c) 2020 Microsoft Corporation
Module Name:
polysat_core.h
Abstract:
Core solver for polysat
Author:
Nikolaj Bjorner (nbjorner) 2020-08-30
Jakob Rath 2021-04-06
--*/
#pragma once
#include "util/dependency.h"
#include "math/dd/dd_pdd.h"
#include "sat/smt/sat_th.h"
#include "sat/smt/polysat_types.h"
#include "sat/smt/polysat_constraints.h"
#include "sat/smt/polysat_viable.h"
#include "sat/smt/polysat_assignment.h"
namespace polysat {
class core;
class solver;
class core {
class mk_add_var;
class mk_dqueue_var;
class mk_assign_var;
class mk_add_watch;
typedef svector<std::pair<unsigned, unsigned>> activity;
friend class viable;
friend class constraints;
friend class assignment;
solver& s;
viable m_viable;
constraints m_constraints;
assignment m_assignment;
unsigned m_qhead = 0, m_vqhead = 0;
svector<dependent_constraint> m_prop_queue;
stacked_dependency_manager<dependency> m_dep;
mutable scoped_ptr_vector<dd::pdd_manager> m_pdd;
dependency_vector m_unsat_core;
// attributes associated with variables
vector<pdd> m_vars; // for each variable a pdd
vector<rational> m_values; // current value of assigned variable
ptr_vector<stacked_dependency> m_justification; // justification for assignment
activity m_activity; // activity of variables
var_queue<activity> m_var_queue; // priority queue of variables to assign
vector<unsigned_vector> m_watch; // watch lists for variables for constraints on m_prop_queue where they occur
vector<pdd> m_subst; // substitution, one for each size.
// values to split on
rational m_value;
pvar m_var = 0;
dd::pdd_manager& sz2pdd(unsigned sz) const;
dd::pdd_manager& var2pdd(pvar v) const;
unsigned size(pvar v) const { return var2pdd(v).power_of_2(); }
void del_var();
bool is_assigned(pvar v) { return nullptr != m_justification[v]; }
void propagate_constraint(unsigned idx, dependent_constraint& dc);
void propagate_value(unsigned idx, dependent_constraint const& dc);
void propagate_assignment(pvar v, rational const& value, stacked_dependency* dep);
bool propagate_unsat_core();
void add_watch(unsigned idx, signed_constraint& sc);
void add_watch(unsigned idx, unsigned var);
lbool eval(signed_constraint sc) { throw default_exception("nyi"); }
dependency_vector explain_eval(dependent_constraint const& dc) { throw default_exception("nyi"); }
public:
core(solver& s);
sat::check_result check();
bool propagate();
void assign_eh(signed_constraint const& sc, dependency const& dep);
expr_ref constraint2expr(signed_constraint const& sc) const { throw default_exception("nyi"); }
pdd value(rational const& v, unsigned sz);
signed_constraint eq(pdd const& p) { return m_constraints.eq(p); }
signed_constraint eq(pdd const& p, pdd const& q) { return m_constraints.eq(p - q); }
signed_constraint ule(pdd const& p, pdd const& q) { return m_constraints.ule(p, q); }
signed_constraint sle(pdd const& p, pdd const& q) { return m_constraints.sle(p, q); }
signed_constraint umul_ovfl(pdd const& p, pdd const& q) { return m_constraints.umul_ovfl(p, q); }
signed_constraint smul_ovfl(pdd const& p, pdd const& q) { return m_constraints.smul_ovfl(p, q); }
signed_constraint smul_udfl(pdd const& p, pdd const& q) { return m_constraints.smul_udfl(p, q); }
signed_constraint bit(pdd const& p, unsigned i) { return m_constraints.bit(p, i); }
pdd lshr(pdd a, pdd b) { throw default_exception("nyi"); }
pdd ashr(pdd a, pdd b) { throw default_exception("nyi"); }
pdd shl(pdd a, pdd b) { throw default_exception("nyi"); }
pdd band(pdd a, pdd b) { throw default_exception("nyi"); }
pdd bxor(pdd a, pdd b) { throw default_exception("nyi"); }
pdd bor(pdd a, pdd b) { throw default_exception("nyi"); }
pdd bnand(pdd a, pdd b) { throw default_exception("nyi"); }
pdd bxnor(pdd a, pdd b) { throw default_exception("nyi"); }
pdd bnor(pdd a, pdd b) { throw default_exception("nyi"); }
pdd bnot(pdd a) { throw default_exception("nyi"); }
std::pair<pdd, pdd> quot_rem(pdd const& n, pdd const& d) { throw default_exception("nyi"); }
pdd zero_ext(pdd a, unsigned sz) { throw default_exception("nyi"); }
pdd sign_ext(pdd a, unsigned sz) { throw default_exception("nyi"); }
pdd extract(pdd src, unsigned hi, unsigned lo) { throw default_exception("nyi"); }
pdd concat(unsigned n, pdd const* args) { throw default_exception("nyi"); }
pvar add_var(unsigned sz);
pdd var(pvar p) { return m_vars[p]; }
<<<<<<< HEAD
=======
unsigned size(pvar v) const { return var2pdd(v).power_of_2(); }
constraints& cs() { return m_constraints; }
trail_stack& trail();
>>>>>>> c7945af45 (porting viable)
std::ostream& display(std::ostream& out) const { throw default_exception("nyi"); }
};
}

475
src/sat/smt/polysat_viable.cpp
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/*++
Copyright (c) 2021 Microsoft Corporation
Module Name:
maintain viable domains
Author:
Nikolaj Bjorner (nbjorner) 2021-03-19
Jakob Rath 2021-04-06
Notes:
--*/
#include "util/debug.h"
#include "util/log.h"
#include "sat/smt/polysat_viable.h"
#include "sat/smt/polysat_core.h"
namespace polysat {
using dd::val_pp;
viable::viable(core& c) : c(c), cs(c.cs()), m_forbidden_intervals(c) {}
viable::~viable() {
for (auto* e : m_alloc)
dealloc(e);
}
std::ostream& operator<<(std::ostream& out, find_t f) {
switch (f) {
case find_t::empty: return out << "empty";
case find_t::singleton: return out << "singleton";
case find_t::multiple: return out << "multiple";
case find_t::resource_out: return out << "resource-out";
default: return out << "<unknown>";
}
}
struct viable::pop_viable_trail : public trail {
viable& m_s;
entry* e;
pvar v;
entry_kind k;
public:
pop_viable_trail(viable& s, entry* e, pvar v, entry_kind k)
: m_s(s), e(e), v(v), k(k) {}
void undo() override {
m_s.pop_viable(e, v, k);
}
};
struct viable::push_viable_trail : public trail {
viable& m_s;
entry* e;
pvar v;
entry_kind k;
public:
push_viable_trail(viable& s, entry* e, pvar v, entry_kind k)
: m_s(s), e(e), v(v), k(k) {}
void undo() override {
m_s.push_viable(e, v, k);
}
};
viable::entry* viable::alloc_entry(pvar var) {
if (m_alloc.empty())
return alloc(entry);
auto* e = m_alloc.back();
e->reset();
e->var = var;
m_alloc.pop_back();
return e;
}
find_t viable::find_viable(pvar v, rational& out_val) {
ensure_var(v);
throw default_exception("nyi");
}
/*
* Explain why the current variable is not viable or signleton.
*/
dependency_vector viable::explain() { throw default_exception("nyi"); }
/*
* Register constraint at index 'idx' as unitary in v.
*/
void viable::add_unitary(pvar v, unsigned idx) {
ensure_var(v);
if (c.is_assigned(v))
return;
auto [sc, d] = c.m_constraint_trail[idx];
entry* ne = alloc_entry(v);
if (!m_forbidden_intervals.get_interval(sc, v, *ne)) {
m_alloc.push_back(ne);
return;
}
if (ne->interval.is_currently_empty()) {
m_alloc.push_back(ne);
return;
}
if (ne->coeff == 1) {
intersect(v, ne);
return;
}
else if (ne->coeff == -1) {
insert(ne, v, m_diseq_lin, entry_kind::diseq_e);
return;
}
else {
unsigned const w = c.size(v);
unsigned const k = ne->coeff.parity(w);
// unsigned const lo_parity = ne->interval.lo_val().parity(w);
// unsigned const hi_parity = ne->interval.hi_val().parity(w);
display_one(std::cerr << "try to reduce entry: ", v, ne) << "\n";
if (k > 0 && ne->coeff.is_power_of_two()) {
// reduction of coeff gives us a unit entry
//
// 2^k a x \not\in [ lo ; hi [
//
// new_lo = lo[w-1:k] if lo[k-1:0] = 0
// lo[w-1:k] + 1 otherwise
//
// new_hi = hi[w-1:k] if hi[k-1:0] = 0
// hi[w-1:k] + 1 otherwise
//
// Reference: Fig. 1 (dtrim) in BitvectorsMCSAT
//
pdd const& pdd_lo = ne->interval.lo();
pdd const& pdd_hi = ne->interval.hi();
rational const& lo = ne->interval.lo_val();
rational const& hi = ne->interval.hi_val();
rational new_lo = machine_div2k(lo, k);
if (mod2k(lo, k).is_zero())
ne->side_cond.push_back(cs.eq(pdd_lo * rational::power_of_two(w - k)));
else {
new_lo += 1;
ne->side_cond.push_back(~cs.eq(pdd_lo * rational::power_of_two(w - k)));
}
rational new_hi = machine_div2k(hi, k);
if (mod2k(hi, k).is_zero())
ne->side_cond.push_back(cs.eq(pdd_hi * rational::power_of_two(w - k)));
else {
new_hi += 1;
ne->side_cond.push_back(~cs.eq(pdd_hi * rational::power_of_two(w - k)));
}
// we have to update also the pdd bounds accordingly, but it seems not worth introducing new variables for this eagerly
// new_lo = lo[:k] etc.
// TODO: for now just disable the FI-lemma if this case occurs
ne->valid_for_lemma = false;
if (new_lo == new_hi) {
// empty or full
// if (ne->interval.currently_contains(rational::zero()))
NOT_IMPLEMENTED_YET();
}
ne->coeff = machine_div2k(ne->coeff, k);
ne->interval = eval_interval::proper(pdd_lo, new_lo, pdd_hi, new_hi);
ne->bit_width -= k;
display_one(std::cerr << "reduced entry: ", v, ne) << "\n";
LOG("reduced entry to unit in bitwidth " << ne->bit_width);
intersect(v, ne);
}
// TODO: later, can reduce according to shared_parity
// unsigned const shared_parity = std::min(coeff_parity, std::min(lo_parity, hi_parity));
insert(ne, v, m_equal_lin, entry_kind::equal_e);
return;
}
}
void viable::ensure_var(pvar v) {
while (v >= m_units.size()) {
m_units.push_back(layers());
m_equal_lin.push_back(nullptr);
m_diseq_lin.push_back(nullptr);
}
}
bool viable::intersect(pvar v, entry* ne) {
SASSERT(!c.is_assigned(v));
SASSERT(!ne->src.empty());
entry*& entries = m_units[v].ensure_layer(ne->bit_width).entries;
entry* e = entries;
if (e && e->interval.is_full()) {
m_alloc.push_back(ne);
return false;
}
if (ne->interval.is_currently_empty()) {
m_alloc.push_back(ne);
return false;
}
auto create_entry = [&]() {
c.trail().push(pop_viable_trail(*this, ne, v, entry_kind::unit_e));
ne->init(ne);
return ne;
};
auto remove_entry = [&](entry* e) {
c.trail().push(push_viable_trail(*this, e, v, entry_kind::unit_e));
e->remove_from(entries, e);
e->active = false;
};
if (ne->interval.is_full()) {
// for (auto const& l : m_units[v].get_layers())
// while (l.entries)
// remove_entry(l.entries);
while (entries)
remove_entry(entries);
entries = create_entry();
return true;
}
if (!e)
entries = create_entry();
else {
entry* first = e;
do {
if (e->interval.currently_contains(ne->interval)) {
m_alloc.push_back(ne);
return false;
}
while (ne->interval.currently_contains(e->interval)) {
entry* n = e->next();
remove_entry(e);
if (!entries) {
entries = create_entry();
return true;
}
if (e == first)
first = n;
e = n;
}
SASSERT(e->interval.lo_val() != ne->interval.lo_val());
if (e->interval.lo_val() > ne->interval.lo_val()) {
if (first->prev()->interval.currently_contains(ne->interval)) {
m_alloc.push_back(ne);
return false;
}
e->insert_before(create_entry());
if (e == first)
entries = e->prev();
SASSERT(well_formed(m_units[v]));
return true;
}
e = e->next();
} while (e != first);
// otherwise, append to end of list
first->insert_before(create_entry());
}
SASSERT(well_formed(m_units[v]));
return true;
}
void viable::log() {
for (pvar v = 0; v < m_units.size(); ++v)
log(v);
}
void viable::log(pvar v) {
throw default_exception("nyi");
}
viable::layer& viable::layers::ensure_layer(unsigned bit_width) {
for (unsigned i = 0; i < m_layers.size(); ++i) {
layer& l = m_layers[i];
if (l.bit_width == bit_width)
return l;
else if (l.bit_width < bit_width) {
m_layers.push_back(layer(0));
for (unsigned j = m_layers.size(); --j > i; )
m_layers[j] = m_layers[j - 1];
m_layers[i] = layer(bit_width);
return m_layers[i];
}
}
m_layers.push_back(layer(bit_width));
return m_layers.back();
}
viable::layer* viable::layers::get_layer(unsigned bit_width) {
return const_cast<layer*>(std::as_const(*this).get_layer(bit_width));
}
viable::layer const* viable::layers::get_layer(unsigned bit_width) const {
for (layer const& l : m_layers)
if (l.bit_width == bit_width)
return &l;
return nullptr;
}
void viable::pop_viable(entry* e, pvar v, entry_kind k) {
SASSERT(well_formed(m_units[v]));
SASSERT(e->active);
e->active = false;
switch (k) {
case entry_kind::unit_e:
entry::remove_from(m_units[v].get_layer(e)->entries, e);
SASSERT(well_formed(m_units[v]));
break;
case entry_kind::equal_e:
entry::remove_from(m_equal_lin[v], e);
break;
case entry_kind::diseq_e:
entry::remove_from(m_diseq_lin[v], e);
break;
default:
UNREACHABLE();
break;
}
m_alloc.push_back(e);
}
void viable::push_viable(entry* e, pvar v, entry_kind k) {
// display_one(verbose_stream() << "Push entry: ", v, e) << "\n";
entry*& entries = m_units[v].get_layer(e)->entries;
SASSERT(e->prev() != e || !entries);
SASSERT(e->prev() != e || e->next() == e);
SASSERT(k == entry_kind::unit_e);
SASSERT(!e->active);
e->active = true;
(void)k;
SASSERT(well_formed(m_units[v]));
if (e->prev() != e) {
entry* pos = e->prev();
e->init(e);
pos->insert_after(e);
if (e->interval.lo_val() < entries->interval.lo_val())
entries = e;
}
else
entries = e;
SASSERT(well_formed(m_units[v]));
}
void viable::insert(entry* e, pvar v, ptr_vector<entry>& entries, entry_kind k) {
SASSERT(well_formed(m_units[v]));
c.trail().push(pop_viable_trail(*this, e, v, k));
e->init(e);
if (!entries[v])
entries[v] = e;
else
e->insert_after(entries[v]);
SASSERT(entries[v]->invariant());
SASSERT(well_formed(m_units[v]));
}
std::ostream& viable::display_one(std::ostream& out, pvar v, entry const* e) const {
auto& m = c.var2pdd(v);
if (e->coeff == -1) {
// p*val + q > r*val + s if e->src.is_positive()
// p*val + q >= r*val + s if e->src.is_negative()
// Note that e->interval is meaningless in this case,
// we just use it to transport the values p,q,r,s
rational const& p = e->interval.lo_val();
rational const& q_ = e->interval.lo().val();
rational const& r = e->interval.hi_val();
rational const& s_ = e->interval.hi().val();
out << "[ ";
out << val_pp(m, p, true) << "*v" << v << " + " << val_pp(m, q_);
out << (e->src[0].is_positive() ? " > " : " >= ");
out << val_pp(m, r, true) << "*v" << v << " + " << val_pp(m, s_);
out << " ] ";
}
else if (e->coeff != 1)
out << e->coeff << " * v" << v << " " << e->interval << " ";
else
out << e->interval << " ";
if (e->side_cond.size() <= 5)
out << e->side_cond << " ";
else
out << e->side_cond.size() << " side-conditions ";
unsigned count = 0;
for (const auto& src : e->src) {
++count;
out << src << "; ";
if (count > 10) {
out << " ...";
break;
}
}
return out;
}
std::ostream& viable::display_all(std::ostream& out, pvar v, entry const* e, char const* delimiter) const {
if (!e)
return out;
entry const* first = e;
unsigned count = 0;
do {
display_one(out, v, e) << delimiter;
e = e->next();
++count;
if (count > 10) {
out << " ...";
break;
}
}
while (e != first);
return out;
}
/*
* Lower bounds are strictly ascending.
* Intervals don't contain each-other (since lower bounds are ascending, it suffices to check containment in one direction).
*/
bool viable::well_formed(entry* e) {
if (!e)
return true;
entry* first = e;
while (true) {
if (!e->active)
return false;
if (e->interval.is_full())
return e->next() == e;
if (e->interval.is_currently_empty())
return false;
auto* n = e->next();
if (n != e && e->interval.currently_contains(n->interval))
return false;
if (n == first)
break;
if (e->interval.lo_val() >= n->interval.lo_val())
return false;
e = n;
}
return true;
}
/*
* Layers are ordered in strictly descending bit-width.
* Entries in each layer are well-formed.
*/
bool viable::well_formed(layers const& ls) {
unsigned prev_width = std::numeric_limits<unsigned>::max();
for (layer const& l : ls.get_layers()) {
if (!well_formed(l.entries))
return false;
if (!all_of(dll_elements(l.entries), [&l](entry const& e) { return e.bit_width == l.bit_width; }))
return false;
if (prev_width <= l.bit_width)
return false;
prev_width = l.bit_width;
}
return true;
}
}