gistfile1.txt

Firstly I know that having a C extension in JRUBY is not a great idea, however, I am kind of being forced in a way.

I have a system at the moment that uses a Ruby KDTree https://github.com/MagLev/maglev/tree/master/examples/persistence/kdtree/

It works, but its not very quick. I am using Jruby because of its great performance and would love to stay with it.

To improve the speed of the KDTree, I found and used https://github.com/consti/tupalo-kdtree which is crazy quick, it also has the same syntax for use http://rubydoc.info/gems/tupalo-kdtree/0.2.3/frames and it works great under MRI 1.9.3 - it brings down on benchmark from 30 seconds to around 0.01 seconds.

However when I try and load this gem in Jruby it only works to load using JRUBY_OPTS=--1.8 - which is odd, but it loads find and installs.

However when I run the attached code, it runs incredibly slow. unless you decrease the number of objects going into the KDTree - almost as if it runs out of memory?

require 'rubygems'
require "benchmark"

gem 'tupalo-kdtree'
require 'kdtree'

#set the number of lat/lngs to go into KDTree
 @kdsize = 10000000

# sets up random lat longs and loads them into the KDTree - len = number of lat/lngs
  def setup_tree(len)
    @points = (0...len).map { |i| [rand_coord, rand_coord, i ] }
    @kdtree = KDTree.new(@points)
  end


# little method to generate random lat/lngs
  def rand_coord
    rand(0) * 10 - 5
  end

# looks up random lat long to find nearest neighbour inside KDTree

  def test_nearestk
    pt = []
    @list = []
    2000.times do
      pt = [rand_coord, rand_coord]
      @list << @kdtree.nearest(pt[0],pt[1])
      end
  end
 
#create KDTree (takes the longest)
setup_tree(@kdsize)

#Benchmark the time it takes to lookup @list for nearest neighboard in @kdtree
Benchmark.bm do |x|
  x.report do
  test_nearestk
  end
end

If you change @kdsize to 1000 it works pretty well!

I do not know why this doesn't run will inside of Jruby, and if it is a really stupid idea can someone think of an alternative? I am a bit stuck! But would love to get away from the 30 seconds it takes to run the original ruby code and use the C code.

This is my first post in here, sorry if it is too much!

Thanks Charlie