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#ifndef FIXPOINT_ALGORITHM_HPP
#define FIXPOINT_ALGORITHM_HPP
#include "IdSet.hpp"
#include "IdMap.hpp"
#include "VariableAssignment.hpp"
#include "EquationSystem.hpp"
template<typename Domain>
struct FixpointAlgorithm {
virtual ~FixpointAlgorithm() { }
virtual VariableAssignment<Domain>* maxFixpoint(const EquationSystem<Domain>&) const = 0;
};
template<typename Domain>
struct NaiveFixpointAlgorithm : public FixpointAlgorithm<Domain> {
virtual VariableAssignment<Domain>* maxFixpoint(const EquationSystem<Domain>& system) const {
VariableAssignment<Domain>* rho = NULL;
VariableAssignment<Domain>* result = system.assignment(infinity<Domain>());
do {
if (rho) delete rho;
rho = result;
result = system.eval(*rho);
} while (!system.equalAssignments(*rho, *result));
if (rho) delete rho;
return result;
}
};
template<typename Domain>
struct SmartFixpointAlgorithm : public FixpointAlgorithm<Domain> {
struct DynamicVariableAssignment : public VariableAssignment<Domain> {
DynamicVariableAssignment(const EquationSystem<Domain>& system)
: _system(system),
_values(system.variableCount(), infinity<Domain>()),
_stable(system.variableCount()),
_influence(system.variableCount(), IdSet<Variable<Domain> >(system.variableCount())) { }
const Domain& operator[](const Variable<Domain>& var) const {
solve(var);
//std::cout << _values << std::endl;
return _values[var];
}
private:
void solve(const Variable<Domain>& x) const {
if (!_stable.contains(x)) {
_stable.insert(x);
Domain val = _system[x]->eval(DependencyAssignment(*this, x));
if (val != _values[x]) {
IdSet<Variable<Domain> > oldInfluence = _influence[x];
_influence[x].clear();
_values[x] = val;
_stable.filter(oldInfluence);
for (typename IdSet<Variable<Domain> >::iterator it = oldInfluence.begin();
it != oldInfluence.end();
++it) {
solve(_system.variable(*it));
}
}
}
}
struct DependencyAssignment : public VariableAssignment<Domain> {
DependencyAssignment(const DynamicVariableAssignment& assignment, const Variable<Domain>& var)
: _assignment(assignment), _var(var) { }
const Domain& operator[](const Variable<Domain>& x) const {
const Domain& result = _assignment[x];
_assignment._influence[x].insert(_var);
return result;
}
private:
const DynamicVariableAssignment& _assignment;
const Variable<Domain>& _var;
};
const EquationSystem<Domain>& _system;
mutable IdMap<Variable<Domain>,Domain> _values;
mutable IdSet<Variable<Domain> > _stable;
mutable IdMap<Variable<Domain>,IdSet<Variable<Domain> > > _influence;
};
virtual VariableAssignment<Domain>* maxFixpoint(const EquationSystem<Domain>& system) const {
return new DynamicVariableAssignment(system);
}
};
#endif
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