
Boost Users : 
Subject: Re: [Boostusers] can not compile nearest neighbors in d dimensions
From: Mateusz Åoskot (mateusz_at_[hidden])
Date: 20140416 09:27:01
On 16 April 2014 14:32, Georgios Samaras <georgesamarasdit_at_[hidden]> wrote:
> Thanks for the replies, now it is clearer. However, the minimum dimension I
> have in my datasets is 100 and I want to run NN with dimension 10000.
>
> So, how I am going to initialize a point?
>
> template <int CompileTimeDimension>
> void fill(point& tmp)
> {
> for(int j = CompileTimeDimension  1 ; j >= 0 ; j) {
> bg::set<CompileTimeDimension>(tmp, 5);
> }
> }
>
> Even I can see that the above code won't even compile. Writting manually
> bg::set<0>(tmp, 5), ..., bg::set<10000>(tmp, 5) does not really sound a good
> idea. So what should I do?
Once again, dimension is a compiletime property.
#include <boost/geometry/geometries/point.hpp>
#include <boost/geometry/algorithms/assign.hpp>
namespace bg = boost::geometry;
template <std::size_t D, std::size_t N>
struct fill
{
template <typename Point>
static void apply(Point& p, typename
bg::coordinate_type<Point>::type const& v)
{
bg::set<D>(p, v);
fill<D + 1, N>::apply(p, v);
}
};
template <std::size_t N>
struct fill<N, N>
{
template <typename Point>
static void apply(Point&, typename
bg::coordinate_type<Point>::type const&) {}
};
int main()
{
bg::model::point<double, 1000, bg::cs::cartesian> p1;
fill<0, 1000>::apply(p1, 5);
return 0;
}
But, you will likely hit compiler limits asking for 10K dimensions.
> Maybe boost nearest's neighbors are meant to be used in higher dimensions?
Your problem has *nothing* to do with the NN algorithm as it is
implemented in Boost.Geometry.
Best regards,
 Mateusz Åoskot, http://mateusz.loskot.net
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