add tests and benchmark

Author: annikoff

.gitignore

@@ -1,4 +1,5 @@
 /.idea/
 /.ruby-version
 /.ruby-gemset
-/tmp
+/tmp
+/bin

README.rdoc

@@ -38,6 +38,16 @@ Percentile calculations are based on the NIST formula[http://www.itl.nist.gov/di
 
 * <tt>sudo gem install bkoski-array_stats --source http://gemcutter.org</tt>
 
+== BENCHMARK
+
+A comparison of percentile and fast_percentile methods.
+
+```
+       user     system      total        real
+Ruby:  23.580000   0.480000  24.060000 ( 24.063252)
+Golang:  13.940000   0.440000  14.380000 ( 12.710602)
+```
+
 == LICENSE:
 
 (The MIT License)

Rakefile

@@ -4,7 +4,9 @@ require 'rubygems'
 require 'rake'
 
 gem = Gem::Specification.load(File.dirname(__FILE__) + '/array_stats.gemspec')
-Rake::ExtensionTask.new('array_stats', gem)
+Rake::ExtensionTask.new('array_stats', gem) do |ext|
+  ext.lib_dir = 'bin'
+end
 
 begin
   require 'jeweler'

benchmark

@@ -0,0 +1,15 @@
+#!/usr/bin/env ruby
+require 'benchmark'
+require_relative 'lib/array_stats'
+
+n = 100
+array = (1..1000000).map { rand(10) * 10 }
+Benchmark.bm do |x|
+  x.report('Ruby: ') do
+    n.times { array.percentile(65) }
+  end
+
+  x.report('Golang: ') do
+    n.times { array.fast_percentile(65) }
+  end
+end

ext/array_stats/extconf.rb

@@ -1,4 +1,4 @@
 require 'mkmf'
 find_executable('go')
-%x(go build -buildmode=c-shared -o libfastpercentile.so fast_percentile.go)
-create_makefile('ext/array_stats/fast_percentile')
+%x{go build -buildmode=c-shared -o libfastpercentile.so fast_percentile.go}
+create_makefile('array_stats/array_stats')

ext/array_stats/fast_percentile.go

@@ -19,7 +19,7 @@ func fast_percentile(array unsafe.Pointer, size int, percent float64) float64 {
 	sort.Float64s(elements)
 	length := float64(len(elements))
 	if length == 0 {
-		return 0.0
+		return 0
 	}
 	rank := (percent / 100) * (length + 1)
 	_, rank_frac := math.Modf(rank)

lib/array_stats/array_stats.rb

@@ -2,7 +2,7 @@
 
 module ArrayStats
   extend FFI::Library
-  ffi_lib '../ext/array_stats/libfastpercentile.so'
+  ffi_lib File.expand_path('../../../bin/libfastpercentile.so', __FILE__)
   attach_function :fast_percentile, [:pointer, :int, :double], :double
 
   # Returns the sum of all elements in the array; 0 if array is empty
@@ -35,12 +35,11 @@ def fast_median
   #
   # Algorithm from NIST[http://www.itl.nist.gov/div898/handbook/prc/section2/prc252.htm]
   def percentile p
+    return nil if length == 0
     sorted_array = self.sort
     rank = (p.to_f / 100) * (self.length + 1)
 
-    if self.length == 0
-      return nil
-    elsif rank.fractional_part?
+    if rank.fractional_part?
       sample_0 = sorted_array[rank.truncate - 1]
       sample_1 = sorted_array[rank.truncate]
 
@@ -51,9 +50,9 @@ def percentile p
   end
 
   def fast_percentile p
+    return nil if length == 0
     pointer = FFI::MemoryPointer.new :double, size
     pointer.put_array_of_double 0, self
     ArrayStats.fast_percentile pointer, size, p
   end
-  
-end
+end

test/test_array_stats.rb

@@ -4,67 +4,70 @@ class TestArrayStats < Test::Unit::TestCase
   context "median" do
     should "return the middle of the set if array length is odd" do
       assert_equal 15, [1,2,15,22,38].median
+      assert_equal 15, [1,2,15,22,38].fast_median
     end
-    
+
     should "return the average of the middle of the set if array length is even" do
       assert_equal 10, [1,6,14,22].median
+      assert_equal 10, [1,6,14,22].fast_median
     end
-    
+
     should "return nil if the array is empty" do
       assert_nil [].median
+      assert_nil [].fast_median
     end
-    
+
     should "sort an array before deriving the median" do
       assert_equal 20, [1,20,50,60,10].median
+      assert_equal 20.0, [1,20,50,60,10].fast_median
     end
   end
-  
-  context "percentile" do 
+
+  context "percentile" do
     should "choose the number at a particular rank if array divides cleanly" do
       assert_equal 36, [12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48].percentile(65)
+      assert_equal 36, [12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48].fast_percentile(65)
     end
-    
+
     should "interpolate according to algorithm if array does not divide cleanly" do
       assert_equal 5.5, [3,5,7,8,9,11,13,15].percentile(25)
+      assert_equal 5.5, [3,5,7,8,9,11,13,15].fast_percentile(25)
       assert_equal 95.1981, [95.1772,95.1567,95.1937,95.1959,95.1442,95.0610,95.1591,95.1195,95.1065,95.0925,95.1990,95.1682].percentile(90).round_to(0.0001)
+      assert_equal 95.1981, [95.1772,95.1567,95.1937,95.1959,95.1442,95.0610,95.1591,95.1195,95.1065,95.0925,95.1990,95.1682].fast_percentile(90).round_to(0.0001)
     end
-    
+
     should "return nil if the array is empty" do
       assert_nil [].percentile(30)
+      assert_nil [].fast_percentile(30)
     end
   end
-  
+
   context "total_sum" do
     should "return the sum of all elements in the array" do
       assert_equal 12, [2,4,6].total_sum
     end
-    
+
     should "return an integer if all elements are ints" do
       assert_kind_of Integer, [2,4,6].total_sum
     end
-    
+
     should "return a float if at least some of the elements are floats" do
       assert_kind_of Float, [2.5,3.5,6].total_sum
     end
-    
+
     should "return 0 if the array is empty" do
       assert_equal 0, [].total_sum
     end
   end
-  
+
   context "mean" do
     should "return the mean for the array " do
       assert_equal 7, [2,4,6,8,10,12].mean
       assert_equal 25, [48,29,26,19,3].mean
     end
-    
+
     should "return nil if the array is empty" do
       assert_nil [].mean
     end
   end
-  
-  
-  
 end
-
-

test/test_float_extensions.rb

@@ -7,24 +7,24 @@ class TestFloatExtensions < Test::Unit::TestCase
       n = 1.249
       assert n.fractional_part?
     end
-    
+
     should "return true for a number without a fractional part" do
        n = 1.0
        assert !n.fractional_part?
      end
   end
-  
+
   context "fractional_part" do
     should "return the decimal parts for a number" do
       n = 12.2456
       assert_in_delta 0.2456, n.fractional_part, 0.00000001
     end
-    
+
     should "retrun the decimal parts, even if they are 0" do
       n = 12.0
       assert_equal 0.0, n.fractional_part
     end
-    
+
     should "retrun the decimal as a positive number, even if the original float is negative" do
       n = -12.2399
       assert_in_delta 0.2399, n.fractional_part, 0.00000001

test/test_helper.rb

@@ -2,4 +2,4 @@
 require 'test/unit'
 require File.dirname(__FILE__) + '/../lib/array_stats'
 require 'shoulda'
-require 'facets'
+require 'facets'