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fixing overflow checking

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2017-07-07 13:53:26 -07:00
parent 53c38f02d5
commit 55f54b4fdc
2 changed files with 80 additions and 56 deletions
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125
src/sat/ba_solver.cpp
View file

@ -873,38 +873,40 @@ namespace sat {
m_active_vars.shrink(j);
}
void ba_solver::inc_coeff(literal l, int64 offset) {
void ba_solver::inc_coeff(literal l, unsigned offset) {
SASSERT(offset > 0);
bool_var v = l.var();
SASSERT(v != null_bool_var);
if (static_cast<bool_var>(m_coeffs.size()) <= v) {
m_coeffs.resize(v + 1, 0);
}
m_coeffs.reserve(v + 1, 0);
int64 coeff0 = m_coeffs[v];
if (coeff0 == 0) {
m_active_vars.push_back(v);
}
int64 inc = l.sign() ? -offset : offset;
int64 loffset = static_cast<int64>(offset);
int64 inc = l.sign() ? -loffset : loffset;
int64 coeff1 = inc + coeff0;
m_coeffs[v] = coeff1;
if (coeff1 > INT_MAX || coeff1 < INT_MIN) {
std::cout << "overflow update coefficient " << coeff1 << "\n";
std::cout << "overflow update coefficient " << coeff1 << " offset: " << offset << " coeff0: " << coeff0 << "\n";
UNREACHABLE();
m_overflow = true;
return;
}
if (coeff0 > 0 && inc < 0) {
m_bound -= coeff0 - std::max(0LL, coeff1);
inc_bound(std::max(0LL, coeff1) - coeff0);
}
else if (coeff0 < 0 && inc > 0) {
m_bound -= std::min(0LL, coeff1) - coeff0;
inc_bound(coeff0 - std::min(0LL, coeff1));
}
// reduce coefficient to be no larger than bound.
if (coeff1 > m_bound) {
if (coeff1 > static_cast<int64>(m_bound)) {
m_coeffs[v] = m_bound;
}
else if (coeff1 < 0 && -coeff1 > m_bound) {
else if (coeff1 < 0 && -coeff1 > static_cast<int64>(m_bound)) {
m_coeffs[v] = m_bound;
}
}
@ -913,8 +915,13 @@ namespace sat {
return m_coeffs.get(v, 0);
}
int64 ba_solver::get_abs_coeff(bool_var v) const {
return abs(get_coeff(v));
unsigned ba_solver::get_abs_coeff(bool_var v) const {
int64 c = get_coeff(v);
if (c < INT_MIN+1 || c > UINT_MAX) {
m_overflow = true;
return UINT_MAX;
}
return static_cast<unsigned>(abs(c));
}
int ba_solver::get_int_coeff(bool_var v) const {
@ -927,13 +934,22 @@ namespace sat {
return static_cast<int>(c);
}
unsigned ba_solver::get_bound() const {
if (m_bound < 0 || m_bound > UINT_MAX) {
std::cout << "overflow bound " << m_bound << "\n";
void ba_solver::inc_bound(int64 i) {
if (i < INT_MIN || i > INT_MAX) {
m_overflow = true;
return 1;
return;
}
int64 new_bound = m_bound;
new_bound += i;
if (new_bound < 0) {
m_bound = 0;
}
else if (new_bound > UINT_MAX) {
m_overflow = true;
}
else {
m_bound = static_cast<unsigned>(new_bound);
}
return static_cast<unsigned>(m_bound);
}
void ba_solver::reset_coeffs() {
@ -965,14 +981,14 @@ namespace sat {
}
literal_vector const& lits = s().m_trail;
unsigned idx = lits.size() - 1;
int64 offset = 1;
unsigned offset = 1;
DEBUG_CODE(active2pb(m_A););
unsigned init_marks = m_num_marks;
do {
if (m_overflow || offset > (1 << 12)) {
if (m_overflow || offset > (1 << 12) || m_bound == 0) {
IF_VERBOSE(20, verbose_stream() << "offset: " << offset << "\n";
active2pb(m_A);
display(verbose_stream(), m_A);
@ -987,9 +1003,8 @@ namespace sat {
TRACE("sat_verbose", display(tout, m_A););
TRACE("sat", tout << "process consequent: " << consequent << ":\n"; s().display_justification(tout, js) << "\n";);
SASSERT(offset > 0);
SASSERT(m_bound >= 0);
DEBUG_CODE(justification2pb(js, consequent, offset, m_B););
// DEBUG_CODE(justification2pb(js, consequent, offset, m_B););
if (_debug_conflict) {
std::cout << consequent << "\n";
@ -1000,23 +1015,23 @@ namespace sat {
switch(js.get_kind()) {
case justification::NONE:
SASSERT (consequent != null_literal);
m_bound += offset;
inc_bound(offset);
break;
case justification::BINARY:
m_bound += offset;
inc_bound(offset);
SASSERT (consequent != null_literal);
inc_coeff(consequent, offset);
process_antecedent(js.get_literal(), offset);
break;
case justification::TERNARY:
m_bound += offset;
inc_bound(offset);
SASSERT (consequent != null_literal);
inc_coeff(consequent, offset);
process_antecedent(js.get_literal1(), offset);
process_antecedent(js.get_literal2(), offset);
break;
case justification::CLAUSE: {
m_bound += offset;
inc_bound(offset);
clause & c = *(s().m_cls_allocator.get_clause(js.get_clause_offset()));
unsigned i = 0;
if (consequent != null_literal) {
@ -1041,14 +1056,14 @@ namespace sat {
switch (cnstr.tag()) {
case card_t: {
card& c = cnstr.to_card();
m_bound += offset * c.k();
inc_bound(static_cast<int64>(offset) * c.k());
process_card(c, offset);
break;
}
case pb_t: {
pb& p = cnstr.to_pb();
m_lemma.reset();
m_bound += offset;
inc_bound(offset);
inc_coeff(consequent, offset);
get_antecedents(consequent, p, m_lemma);
TRACE("sat", display(tout, p, true); tout << m_lemma << "\n";);
@ -1062,7 +1077,7 @@ namespace sat {
case xor_t: {
// jus.push_back(js);
m_lemma.reset();
m_bound += offset;
inc_bound(offset);
inc_coeff(consequent, offset);
get_xor_antecedents(consequent, idx, js, m_lemma);
for (literal l : m_lemma) process_antecedent(~l, offset);
@ -1115,7 +1130,8 @@ namespace sat {
js = s().m_justification[v];
offset = get_abs_coeff(v);
if (offset > m_bound) {
m_coeffs[v] = (get_coeff(v) < 0) ? -m_bound : m_bound;
int64 bound64 = static_cast<int64>(m_bound);
m_coeffs[v] = (get_coeff(v) < 0) ? -bound64 : bound64;
offset = m_bound;
DEBUG_CODE(active2pb(m_A););
}
@ -1196,8 +1212,8 @@ namespace sat {
bool ba_solver::create_asserting_lemma() {
adjust_conflict_level:
int64 slack = -m_bound;
int64 bound64 = m_bound;
int64 slack = -bound64;
for (bool_var v : m_active_vars) {
slack += get_abs_coeff(v);
}
@ -1214,6 +1230,7 @@ namespace sat {
bool append = coeff != 0 && val != l_undef && (coeff < 0 == is_true);
if (append) {
literal lit(v, !is_true);
unsigned acoeff = get_abs_coeff(v);
if (lvl(lit) == m_conflict_lvl) {
if (m_lemma[0] == null_literal) {
asserting_coeff = abs(coeff);
@ -1269,31 +1286,30 @@ namespace sat {
if (1 == get_abs_coeff(v)) return;
}
SASSERT(0 <= m_bound && m_bound <= UINT_MAX);
unsigned g = 0;
for (unsigned i = 0; g != 1 && i < m_active_vars.size(); ++i) {
bool_var v = m_active_vars[i];
int64 coeff = get_abs_coeff(v);
unsigned coeff = get_abs_coeff(v);
if (coeff == 0) {
continue;
}
if (m_bound < coeff) {
if (m_bound < coeff) {
int64 bound64 = m_bound;
if (get_coeff(v) > 0) {
m_coeffs[v] = m_bound;
m_coeffs[v] = bound64;
}
else {
m_coeffs[v] = -m_bound;
m_coeffs[v] = -bound64;
}
coeff = m_bound;
}
SASSERT(0 < coeff && coeff <= m_bound);
if (g == 0) {
g = static_cast<unsigned>(coeff);
g = coeff;
}
else {
g = u_gcd(g, static_cast<unsigned>(coeff));
g = u_gcd(g, coeff);
}
}
@ -1307,7 +1323,7 @@ namespace sat {
}
}
void ba_solver::process_card(card& c, int64 offset) {
void ba_solver::process_card(card& c, unsigned offset) {
literal lit = c.lit();
SASSERT(c.k() <= c.size());
SASSERT(lit == null_literal || value(lit) == l_true);
@ -1319,11 +1335,18 @@ namespace sat {
inc_coeff(c[i], offset);
}
if (lit != null_literal) {
process_antecedent(~lit, c.k() * offset);
uint64 offset1 = static_cast<uint64>(offset) * c.k();
if (offset1 > UINT_MAX) {
m_overflow = true;
std::cout << "cardinality offset overflow\n";
}
else {
process_antecedent(~lit, static_cast<unsigned>(offset1));
}
}
}
void ba_solver::process_antecedent(literal l, int64 offset) {
void ba_solver::process_antecedent(literal l, unsigned offset) {
SASSERT(value(l) == l_false);
bool_var v = l.var();
unsigned level = lvl(v);
@ -3286,7 +3309,8 @@ namespace sat {
}
bool ba_solver::validate_lemma() {
int64 val = -m_bound;
int64 bound64 = m_bound;
int64 val = -bound64;
reset_active_var_set();
for (bool_var v : m_active_vars) {
if (m_active_var_set.contains(v)) continue;
@ -3326,7 +3350,7 @@ namespace sat {
ba_solver::constraint* ba_solver::active2constraint() {
reset_active_var_set();
svector<wliteral> wlits;
uint64_t sum = 0;
uint64 sum = 0;
if (m_bound == 1) return 0;
if (m_overflow) return 0;
@ -3335,16 +3359,15 @@ namespace sat {
if (m_active_var_set.contains(v) || coeff == 0) continue;
m_active_var_set.insert(v);
literal lit(v, coeff < 0);
wlits.push_back(wliteral(abs(coeff), lit));
sum += abs(coeff);
wlits.push_back(wliteral(get_abs_coeff(v), lit));
sum += get_abs_coeff(v);
}
unsigned k = get_bound();
if (m_overflow || sum >= UINT_MAX/2) {
return 0;
}
else {
return add_pb_ge(null_literal, wlits, k, true);
return add_pb_ge(null_literal, wlits, m_bound, true);
}
}
@ -3384,11 +3407,11 @@ namespace sat {
svector<wliteral> wlits;
for (bool_var v : m_active_vars) {
int coeff = get_int_coeff(v);
wlits.push_back(std::make_pair(abs(coeff), literal(v, coeff < 0)));
wlits.push_back(std::make_pair(get_abs_coeff(v), literal(v, coeff < 0)));
}
std::sort(wlits.begin(), wlits.end(), compare_wlit());
unsigned k = 0;
int sum = 0, sum0 = 0;
uint64 sum = 0, sum0 = 0;
for (wliteral wl : wlits) {
if (sum >= m_bound) break;
sum0 = sum;
@ -3400,7 +3423,7 @@ namespace sat {
}
while (!wlits.empty()) {
wliteral wl = wlits.back();
if (wl.first + sum0 >= get_bound()) break;
if (wl.first + sum0 >= m_bound) break;
wlits.pop_back();
sum0 += wl.first;
}

11
src/sat/ba_solver.h
View file

@ -215,7 +215,7 @@ namespace sat {
unsigned m_conflict_lvl;
svector<int64> m_coeffs;
svector<bool_var> m_active_vars;
int64 m_bound;
unsigned m_bound;
tracked_uint_set m_active_var_set;
literal_vector m_lemma;
literal_vector m_skipped;
@ -366,15 +366,16 @@ namespace sat {
mutable bool m_overflow;
void reset_active_var_set();
void normalize_active_coeffs();
void inc_coeff(literal l, int64 offset);
void inc_coeff(literal l, unsigned offset);
int64 get_coeff(bool_var v) const;
int64 get_abs_coeff(bool_var v) const;
unsigned get_abs_coeff(bool_var v) const;
int get_int_coeff(bool_var v) const;
unsigned get_bound() const;
void inc_bound(int64 i);
literal get_asserting_literal(literal conseq);
void process_antecedent(literal l, int64 offset);
void process_card(card& c, int64 offset);
void process_antecedent(literal l, unsigned offset);
void process_card(card& c, unsigned offset);
void cut();
bool create_asserting_lemma();