void THandler::backtrack( )
{
// Undoes the state of theory atoms if needed
while ( (int)stack.size( ) > trail.size( ) )
{
Enode * e = stack.back( );
stack.pop_back( );
// It was var_True or var_False
if ( e == NULL )
continue;
if ( !e->isTAtom( ) )
continue;
core_solver.popBacktrackPoint( );
assert( e->isTAtom( ) );
assert( e->hasPolarity( ) );
assert( e->getPolarity( ) == l_True
|| e->getPolarity( ) == l_False );
// Reset polarity
e->resetPolarity( );
assert( !e->hasPolarity( ) );
}
checked_trail_size = stack.size( );
}
void THandler::getReason( Lit l, vec< Lit > & reason )
{
#if LAZY_COMMUNICATION
assert( checked_trail_size == stack.size( ) );
assert( static_cast< int >( checked_trail_size ) == trail.size( ) );
#else
#endif
Var v = var(l);
Enode * e = varToEnode( v );
// It must be a TAtom and already disabled
assert( e->isTAtom( ) );
assert( !e->hasPolarity( ) );
assert( e->isDeduced( ) );
assert( e->getDeduced( ) != l_Undef ); // Last assigned deduction
#if LAZY_COMMUNICATION
assert( e->getPolarity( ) != l_Undef ); // Last assigned polarity
assert( e->getPolarity( ) == e->getDeduced( ) ); // The two coincide
#else
#endif
core_solver.pushBacktrackPoint( );
// Assign reversed polarity temporairly
e->setPolarity( e->getDeduced( ) == l_True ? l_False : l_True );
// Compute reason in whatever solver
const bool res = core_solver.assertLit( e, true ) &&
core_solver.check( true );
// Result must be false
if ( res )
{
cout << endl << "unknown" << endl;
exit( 1 );
}
// Get Explanation
vector< Enode * > & explanation = core_solver.getConflict( true );
if ( config.certification_level > 0 )
verifyExplanationWithExternalTool( explanation );
// Reserve room for implied lit
reason.push( lit_Undef );
// Copy explanation
while ( !explanation.empty( ) )
{
Enode * ei = explanation.back( );
explanation.pop_back( );
assert( ei->hasPolarity( ) );
assert( ei->getPolarity( ) == l_True
|| ei->getPolarity( ) == l_False );
bool negate = ei->getPolarity( ) == l_False;
Var v = enodeToVar( ei );
// Toggle polarity for deduced literal
if ( e == ei )
{
assert( e->getDeduced( ) != l_Undef ); // But still holds the deduced polarity
// The deduced literal must have been pushed
// with the the same polarity that has been deduced
reason[ 0 ] = Lit( v, !negate );
}
else
{
assert( ei->hasPolarity( ) ); // Lit in explanation is active
// This assertion might fail if in your theory solver
// you do not skip deduced literals during assertLit
//
// TODO: check ! It could be deduced: by another solver
// For instance BV found conflict and ei was deduced by EUF solver
//
// assert( !ei->isDeduced( ) ); // and not deduced
Lit l = Lit( v, !negate );
reason.push( l );
}
}
core_solver.popBacktrackPoint( );
// Resetting polarity
e->resetPolarity( );
}