void cvc_propt::lcnf(const bvt &bv)
{
if(bv.empty()) return;
bvt new_bv;
std::set<literalt> s;
new_bv.reserve(bv.size());
for(bvt::const_iterator it=bv.begin(); it!=bv.end(); it++)
{
if(s.insert(*it).second)
new_bv.push_back(*it);
if(s.find(lnot(*it))!=s.end())
return; // clause satisfied
assert(it->var_no()<_no_variables);
}
assert(!new_bv.empty());
out << "%% lcnf" << std::endl;
out << "ASSERT ";
for(bvt::const_iterator it=new_bv.begin(); it!=new_bv.end(); it++)
{
if(it!=new_bv.begin()) out << " OR ";
out << cvc_literal(*it);
}
out << ";" << std::endl << std::endl;
}
bvt float_utilst::abs(const bvt &src)
{
bvt result=src;
assert(!src.empty());
result[result.size()-1]=const_literal(false);
return result;
}
void dplib_propt::lcnf(const bvt &bv)
{
if(bv.empty())
return;
bvt new_bv;
std::set<literalt> s;
new_bv.reserve(bv.size());
for(bvt::const_iterator it=bv.begin(); it!=bv.end(); it++)
{
if(s.insert(*it).second)
new_bv.push_back(*it);
if(s.find(!*it)!=s.end())
return; // clause satisfied
assert(it->var_no()<=_no_variables);
}
assert(!new_bv.empty());
out << "// lcnf\n";
out << "AXIOM ";
for(bvt::const_iterator it=new_bv.begin(); it!=new_bv.end(); it++)
{
if(it!=new_bv.begin())
out << " | ";
out << dplib_literal(*it);
}
out << ";\n\n";
}
literalt bv_utilst::is_one(const bvt &bv)
{
assert(!bv.empty());
bvt tmp;
tmp=bv;
tmp.erase(tmp.begin(), tmp.begin()+1);
return prop.land(is_zero(tmp), bv[0]);
}
literalt float_utilst::is_zero(const bvt &src)
{
assert(!src.empty());
bvt all_but_sign;
all_but_sign=src;
all_but_sign.resize(all_but_sign.size()-1);
return bv_utils.is_zero(all_but_sign);
}
bvt float_utilst::negate(const bvt &src)
{
bvt result=src;
assert(!src.empty());
literalt &sign_bit=result[result.size()-1];
sign_bit=!sign_bit;
return result;
}
literalt cvc_propt::lxor(const bvt &bv)
{
if(bv.empty()) return const_literal(false);
if(bv.size()==1) return bv[0];
if(bv.size()==2) return lxor(bv[0], bv[1]);
literalt literal=const_literal(false);
forall_literals(it, bv)
literal=lxor(*it, literal);
return literal;
}
literalt smt1_propt::lxor(const bvt &bv)
{
if(bv.empty()) return const_literal(false);
if(bv.size()==1) return bv[0];
out << "\n";
literalt l=new_variable();
out << ":assumption ; lxor" << "\n";
out << " (iff " << smt1_literal(l) << " (xor";
forall_literals(it, bv)
out << " " << smt1_literal(*it);
out << "))" << "\n";
return l;
}
bvt bv_utilst::extension(
const bvt &bv,
std::size_t new_size,
representationt rep)
{
std::size_t old_size=bv.size();
bvt result=bv;
result.resize(new_size);
assert(old_size!=0);
literalt extend_with=
(rep==SIGNED && !bv.empty())?bv[old_size-1]:
const_literal(false);
for(std::size_t i=old_size; i<new_size; i++)
result[i]=extend_with;
return result;
}
bool z3_propt::process_clause(const bvt &bv, bvt &dest)
{
dest.clear();
// empty clause! this is UNSAT
if(bv.empty()) return false;
std::set<literalt> s;
dest.reserve(bv.size());
for(bvt::const_iterator it=bv.begin();
it!=bv.end();
it++)
{
literalt l=*it;
// we never use index 0
assert(l.var_no()!=0);
if(l.is_true())
return true; // clause satisfied
if(l.is_false())
continue;
if(l.var_no()>=_no_variables)
std::cout << "l.var_no()=" << l.var_no() << " _no_variables=" << _no_variables << std::endl;
assert(l.var_no()<_no_variables);
// prevent duplicate literals
if(s.insert(l).second)
dest.push_back(l);
if(s.find(lnot(l))!=s.end())
return true; // clause satisfied
}
return false;
}
void smt1_propt::lcnf(const bvt &bv)
{
out << std::endl;
out << ":assumption ; lcnf" << std::endl;
out << " ";
if(bv.empty())
out << "false ; the empty clause";
else if(bv.size()==1)
out << smt1_literal(bv.front());
else
{
out << "(or";
for(bvt::const_iterator it=bv.begin(); it!=bv.end(); it++)
out << " " << smt1_literal(*it);
out << ")";
}
out << std::endl;
}
void float_utilst::normalization_shift(bvt &fraction, bvt &exponent)
{
#if 0
// this thing is quadratic!
bvt new_fraction=prop.new_variables(fraction.size());
bvt new_exponent=prop.new_variables(exponent.size());
// i is the shift distance
for(std::size_t i=0; i<fraction.size(); i++)
{
bvt equal;
// the bits above need to be zero
for(std::size_t j=0; j<i; j++)
equal.push_back(
!fraction[fraction.size()-1-j]);
// this one needs to be one
equal.push_back(fraction[fraction.size()-1-i]);
// iff all of that holds, we shift here!
literalt shift=prop.land(equal);
// build shifted value
bvt shifted_fraction=bv_utils.shift(fraction, bv_utilst::LEFT, i);
bv_utils.cond_implies_equal(shift, shifted_fraction, new_fraction);
// build new exponent
bvt adjustment=bv_utils.build_constant(-i, exponent.size());
bvt added_exponent=bv_utils.add(exponent, adjustment);
bv_utils.cond_implies_equal(shift, added_exponent, new_exponent);
}
// Fraction all zero? It stays zero.
// The exponent is undefined in that case.
literalt fraction_all_zero=bv_utils.is_zero(fraction);
bvt zero_fraction;
zero_fraction.resize(fraction.size(), const_literal(false));
bv_utils.cond_implies_equal(fraction_all_zero, zero_fraction, new_fraction);
fraction=new_fraction;
exponent=new_exponent;
#else
// n-log-n alignment shifter.
// The worst-case shift is the number of fraction
// bits minus one, in case the faction is one exactly.
assert(!fraction.empty());
unsigned depth=integer2unsigned(address_bits(fraction.size()-1));
if(exponent.size()<depth)
exponent=bv_utils.sign_extension(exponent, depth);
bvt exponent_delta=bv_utils.zeros(exponent.size());
for(int d=depth-1; d>=0; d--)
{
std::size_t distance=(1<<d);
assert(fraction.size()>distance);
// check if first 'distance'-many bits are zeros
const bvt prefix=bv_utils.extract_msb(fraction, distance);
literalt prefix_is_zero=bv_utils.is_zero(prefix);
// If so, shift the zeros out left by 'distance'.
// Otherwise, leave as is.
const bvt shifted=
bv_utils.shift(fraction, bv_utilst::LEFT, distance);
fraction=
bv_utils.select(prefix_is_zero, shifted, fraction);
// add corresponding weight to exponent
assert(d<(signed)exponent_delta.size());
exponent_delta[d]=prefix_is_zero;
}
exponent=bv_utils.sub(exponent, exponent_delta);
#endif
}
