Re: binary search trees & binning

[Army Research Lab]

Have you looked at hash_multimap
(http://www.sgi.com/tech/stl/hash_multimap.html)?  Note that the following
code was beaten out in entourage, without compiling, testing, etc.

struct eqdouble
{
  bool operator()(const double d1, const double d2) const
  {
    double diff = d1 - d2;
    if (diff < 0.0)
        diff = -diff;
    return diff < 0.00001; // Or whatever other epsilon you want.
  }
};

struct hashfunc
{
    // This operator hashes numbers into bins of differing ranges.
    // If all your bins are the same size, use divide.
    size_t operator()(const double &d) const
    {
        if (d < 1.0)
            return 1.0;
        if (d < 3.0)
            return 2.0;
        if (d < 35.0987)
            return 3.0;
        return 4.0;
    }
};

typedef hash_multimap<double, double, hashfunc, eqdouble> map_type;

void lookup(const map_type& Map, const double d)
{
  cout << d << ": ";
  pair<map_type::const_iterator, map_type::const_iterator> p =
    Map.equal_range(d);
  for (map_type::const_iterator i = p.first; i != p.second; ++i)
    cout << (*i).second << " ";
  cout << endl;
}

int main()
{
  map_type M;
  M.insert(map_type::value_type(1.0, 1.0));
  M.insert(map_type::value_type(2.0, 2.0));
  M.insert(map_type::value_type(2.0, 12.0));
  M.insert(map_type::value_type(2.0, 13.0));
  M.insert(map_type::value_type(3.0, 16.0));
  M.insert(map_type::value_type(35.0, 17.0));
  M.insert(map_type::value_type(-56.9, 18.0));
  M.insert(map_type::value_type(42.0, 127.0));

  lookup(M, 1.0);
  lookup(M, 2.0);
  lookup(M, 35.0);
}

Thanks,
Cem Karan

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