SegmentTree

Ruby implementation of segment tree data structure. Segment tree is a tree data structure for storing intervals, or segments. It allows querying which of the stored segments contain a given point. It is, in principle, a static structure; that is, its content cannot be modified once the structure is built.

Segment tree storage has the complexity of O(n). Segment tree querying has the complexity of O(log n).

It's pretty fast on querying trees with ~ 10 millions segments, though building of such big tree will take long. Internally it is not a tree - it is just a sorted array, and querying the tree is just a simple binary search (it was implemented as real tree in versions before 0.1.0, but these trees consumed a lot of memory).

Installation

Add this line to your application's Gemfile:

gem 'segment_tree'

And then execute:

$ bundle

Or install it yourself as:

$ gem install segment_tree

Usage

Segment tree consists of segments (in Ruby it's Range objects) and corresponding values. The easiest way to build a segment tree is to create it from hash where segments are keys:

tree = SegmentTree.new(1..10 => "a", 11..20 => "b", 21..30 => "c") # => #<SegmentTree:0xa47eadc @root=#<SegmentTree::Container:0x523f3b6 @range=1..30>>

After that you can query the tree of which segment contains a given point:

tree.find(5) # => #<SegmentTree::Segment:0xa47ea8c @range=1..10, @value="a">

Real world example

Segment tree can be used in applications where IP-address geocoding is needed.

data = [
  [IPAddr.new('87.224.241.0/24').to_range, {:city => "YEKT"}],
  [IPAddr.new('195.58.18.0/24').to_range, {:city => "MSK"}]
  # and so on
]
ip_tree = SegmentTree.new(data)

client_ip = IPAddr.new("87.224.241.66")
ip_tree.find(client_ip).value # => {:city=>"YEKT"}

Some benchmarks

Building a tree of N intervals

              user     system      total        real
100       0.000000   0.000000   0.000000 (  0.000143)
1000      0.000000   0.000000   0.000000 (  0.001094)
10000     0.010000   0.000000   0.010000 (  0.011446)
100000    0.110000   0.000000   0.110000 (  0.115025)
1000000   1.390000   0.000000   1.390000 (  1.387665)

Finding matching interval in tree of N intervals

              user     system      total        real
100       0.000000   0.000000   0.000000 (  0.000030)
1000      0.000000   0.000000   0.000000 (  0.000017)
10000     0.000000   0.000000   0.000000 (  0.000025)
100000    0.000000   0.000000   0.000000 (  0.000033)
1000000   0.000000   0.000000   0.000000 (  0.000028)

Finding matching interval in list of N intervals using Array.find

              user     system      total        real
100       0.000000   0.000000   0.000000 (  0.000055)
1000      0.000000   0.000000   0.000000 (  0.000401)
10000     0.010000   0.000000   0.010000 (  0.003971)
100000    0.010000   0.000000   0.010000 (  0.003029)
1000000   0.040000   0.000000   0.040000 (  0.038484)

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Added some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request

TODO

Fix README typos and grammatical errors (english speaking contributors are welcomed)
Implement C binding for MRI.

LICENSE

MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

segment_tree

Development