void
closestColumnsAndDistances(
const MappedMatrix& inMatrix,
const MappedColumnVector& inVector,
DistanceFunction& inMetric,
RandomAccessIterator ioFirst,
RandomAccessIterator ioLast) {
ReverseLexicographicComparator<
typename std::iterator_traits<RandomAccessIterator>::value_type>
comparator;
std::fill(ioFirst, ioLast,
std::make_tuple(0, std::numeric_limits<double>::infinity()));
for (Index i = 0; i < inMatrix.cols(); ++i) {
double currentDist
= AnyType_cast<double>(
inMetric(MappedColumnVector(inMatrix.col(i)), inVector)
);
// outIndicesAndDistances is a heap, so the first element is maximal
if (currentDist < std::get<1>(*ioFirst)) {
// Unfortunately, the STL does not have a decrease-key function,
// so we are wasting a bit of performance here
std::pop_heap(ioFirst, ioLast, comparator);
*(ioLast - 1) = std::make_tuple(i, currentDist);
std::push_heap(ioFirst, ioLast, comparator);
}
}
std::sort_heap(ioFirst, ioLast, comparator);
}
std::tuple<Index, double>
closestColumnAndDistance(
const MappedMatrix& inMatrix,
const MappedColumnVector& inVector,
DistanceFunction& inMetric) {
Index closestColumn = 0;
double minDist = std::numeric_limits<double>::infinity();
for (Index i = 0; i < inMatrix.cols(); ++i) {
double currentDist
= AnyType_cast<double>(
inMetric(MappedColumnVector(inMatrix.col(i)), inVector)
);
if (currentDist < minDist) {
closestColumn = i;
minDist = currentDist;
}
}
return std::tuple<Index, double>(closestColumn, minDist);
}