Method processIdenticalVariables

src/engine/Preprocessor.cpp:590–648

}

bool Preprocessor::processIdenticalVariables()
{
    List<Equation> &equations( _preprocessed->getEquations() );
    List<Equation>::iterator equation = equations.begin();

    bool found = false;
    while ( equation != equations.end() )
    {
        // We are only looking for equations of type c(v1 - v2) = 0
        if ( equation->_addends.size() != 2 || equation->_type != Equation::EQ )
        {
            ++equation;
            continue;
        }

        Equation::Addend term1 = equation->_addends.front();
        Equation::Addend term2 = equation->_addends.back();

        if ( FloatUtils::areDisequal( term1._coefficient, -term2._coefficient ) ||
             !FloatUtils::isZero( equation->_scalar ) )
        {
            ++equation;
            continue;
        }

        ASSERT( term1._variable != term2._variable );

        // The equation matches the pattern, extract the variables
        unsigned v1 = term1._variable;
        unsigned v2 = term2._variable;

        // Input and output variables should not be merged
        if ( _uneliminableVariables.exists( v1 ) || _uneliminableVariables.exists( v2 ) )
        {
            ++equation;
            continue;
        }

        // This equation can be removed
        found = true;

        double bestLowerBound =
            getLowerBound( v1 ) > getLowerBound( v2 ) ? getLowerBound( v1 ) : getLowerBound( v2 );

        double bestUpperBound =
            getUpperBound( v1 ) < getUpperBound( v2 ) ? getUpperBound( v1 ) : getUpperBound( v2 );

        equation = equations.erase( equation );

        setLowerBound( v2, bestLowerBound );
        setUpperBound( v2, bestUpperBound );

        _preprocessed->mergeIdenticalVariables( v1, v2 );

        _mergedVariables[v1] = v2;
    }

    return found;