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SetImagePruner.cpp
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SetImagePruner.cpp
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#include "SetImagePruner.h"
#include <deque>
#include <permlib/search/classic/set_image_search.h>
namespace {
/**
* This predicate returns true if the input subset is in the same orbit as the given representative - ie. whether there
* exists a permutation which maps the representative to the input subset.
*/
class SameOrbitPredicate {
boost::shared_ptr<const Group> G;
Subset rep;
public:
SameOrbitPredicate(const Group& _G, const Subset& _rep) : G(_G.shared_from_this()), rep(_rep) {}
bool operator()(const Subset& candidate) const {
// Must construct the search here, as permlib's search classes are not copyable
permlib::classic::SetImageSearch<PermutationGroup, PermutationGroup::TRANStype> search(G->getGroup(), 0);
search.construct(rep.begin(), rep.end(), candidate.begin(), candidate.end());
return search.searchCosetRepresentative();
}
};
}
SetImagePruner::SetImagePruner(const Group& G, unsigned int k, unsigned long rho, const std::vector<Subset>& orbitReps, const boost::any& prunerData) : Pruner(G, rho, DefaultCandidateGenerator(G.getNumPoints(), orbitReps)) {}
void SetImagePruner::prune() {
newReps = std::vector<Subset>();
newReps->reserve(rho);
const std::vector<Subset>& candidates = getCandidates();
std::deque<Subset> remainingCandidates(candidates.begin(), candidates.end());
while (!remainingCandidates.empty()) {
Subset rep = remainingCandidates.front();
remainingCandidates.pop_front();
newReps->push_back(rep);
// Erase everything in remainingCandidates in the same orbit
remainingCandidates.erase(
std::remove_if(remainingCandidates.begin(), remainingCandidates.end(), SameOrbitPredicate(*G, rep)),
remainingCandidates.end());
}
}
std::vector<Subset> SetImagePruner::getNewReps() {
if (!newReps) boost::throw_exception(PrunerNotReady());
return *newReps;
}
size_t SetImagePruner::getColumn(const Subset& candidate) {
std::vector<Subset>::iterator findIt = std::find_if(newReps->begin(), newReps->end(), SameOrbitPredicate(*G, candidate));
// findIt should not be newReps->end()
return std::distance(newReps->begin(), findIt);
}