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hacky bug fix in max constraint #84

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Aug 7, 2018
Merged

hacky bug fix in max constraint #84

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18 changes: 18 additions & 0 deletions src/engine/MaxConstraint.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -266,6 +266,24 @@ void MaxConstraint::getEntailedTightenings( List<Tightening> &tightenings ) cons
// fLB cannot be smaller than maxElementLB
if ( FloatUtils::lt( fLB, maxElementLB ) )
tightenings.append( Tightening( _f, maxElementLB, Tightening::LB ) );
else if ( _elements.size() == 1 )
{
// Special case: there is only one element. In that case, the tighter lower
// bound (in this case, f's) wins.
tightenings.append( Tightening( *_elements.begin(), fLB, Tightening::LB ) );
}

// Hack:
// MaxConstraint currently does some 'illegal' internal bound propgation
// (in eliminateVariable()) due to bound notifications, and doesn't bother
// informing the outside world. To work around this, we report the tighest
// internal bounds known for f (knowing that these will be ignored by the
// outside world if tighter bounds are already known).

if ( _lowerBounds.exists( _f ) )
tightenings.append( Tightening( _f, _lowerBounds[_f], Tightening::LB ) );
if ( _upperBounds.exists( _f ) )
tightenings.append( Tightening( _f, _upperBounds[_f], Tightening::UB ) );

// TODO: can we derive additional bounds?
}
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