jruby: enhancing java developers' lives

JRuby:Enhancing Java Developers' Lives

Hiro Asari@hiro_asariJRuby Support EngineerEngine Yard@engineyard

Wednesday, November 16, 11

JRuby: a Brief History

Where it came from, and where it is now


History• September 10, 2001Source:(Wikipedia


History


History• 10+ years old• Led by Charles Nutter and

Tom Enebo• 14.800+ commits


Project Status• Current Stable Release:

1.6.5• Compatible with Ruby

1.8.7 and 1.9.2• Supports Rails 3.1


Getting JRuby

h0p://jruby.org/download


http://jruby.org/download

http://jruby.org/download

Trying JRubyh0p://jruby.org/tryjruby


http://jruby.org/tryjruby

http://jruby.org/tryjruby

Book


Quick Tour of Ruby

A brief overview of the language


Classes

public class Circle extends Shape { private final int radius;

public Circle(int radius) { this.radius = radius; } public int getRadius() { return radius; } public double getArea() { return Math.PI * Math.pow(radius,2); } public static void main(String[] a) { double area=new Circle(2).getArea(); System.out.println(area); }}

class Circle < Shape def initialize(radius) @radius = radius end attr_reader :radius

def area Math::PI*(@radius ** 2) endend

puts Circle.new(2).area


Single Inheritance






Same Thing


Constructor







No Type Declarations







Instance Variables






‘@’ == ‘this.’ and is mandatory


Working with Instance Variables






Common tasks are easy


Symbols:identifier

• Prefixed with a colon• Uniquely defined in a runtime


Point of No Return






Last Expression is always return value


.new is just a class method







Blocks/Closures• Pass an anonymous function to a method call

# Look mom...no boilerplate!my_open(file) do |io| first_line = io.gets # ...end

def my_open(file, mode='r') io = File.open(file) yield ioensure io.closeend

letters.group_by {|b| b.zip_code }

button.action_performed do exitend


dude = people.find { |person| person.id == 123 }

floats = [1,2].collect { |int| int.to_f } # => [1.0, 2.0]

Modules

module Enumerable def find(if_none = nil) each { |o| return o if yield(o) } if_none end

# Many other methods not shown

def collect ary = [] each { |o| ary << yield(o) } ary endend

class MyTree include Enumerable

# tree impl not shown :)

def each # yield each element # in tree endend


Everything is an Expression

class Color COLORS = {:red => 0xff0000, :green => 0x00ff00, :blue => 0x0000ff}

COLORS.each do |name, value| define_method(name) do value end endend


Classes/Modules are open

class MyTree def each #... endend

#... later in source#... maybe even different file

class MyTree def debug #... endend


Pure OO Language• Everything is an objectMyTree.foo #=> method call12 + 8 #=> here, '+' is a method on Fixnum, 12.12.to_s(8) #=> "14"puts 11.odd? #=> true


JRuby on RailsRuby's Killer app


Java Web Frameworks

Devoxx 2010


Java Web Frameworks

h0p://j.mp/raible<jvm<frameworks

© 2010, Raible DesignsImages by Stuck in Customs - http://www.flickr.com/photos/stuckincustoms

© 2010 Raible Designs

COMPARING JVM WEB FRAMEWORKS

Matt Raiblehttp://raibledesigns.com


http://j.mp/raible-jvm-frameworks

http://j.mp/raible-jvm-frameworks

Install Rails$ jruby -S gem install railsFetching: multi_json-1.0.3.gem (100%)⋮Fetching: bundler-1.0.21.gem (100%)Fetching: rails-3.1.1.gem (100%)Successfully installed multi_json-1.0.3Successfully installed activesupport-3.1.1⋮Successfully installed thor-0.14.6Successfully installed rack-ssl-1.3.2Successfully installed json-1.6.1-javaSuccessfully installed rdoc-3.11Successfully installed railties-3.1.1Successfully installed bundler-1.0.21Successfully installed rails-3.1.131 gems installed


Generate Rails app$ jruby -S rails new awesomeapp create ⋮ create vendor/plugins create vendor/plugins/.gitkeep run bundle installFetching source index for http://rubygems.org/Using rake (0.9.2.2) ⋮Using json (1.6.1) Using rdoc (3.11) Using thor (0.14.6) Using railties (3.1.1) Installing coffee-rails (3.1.1) Installing jquery-rails (1.0.16) Installing jruby-openssl (0.7.4) Using rails (3.1.1) Installing sass (3.1.10) Installing sass-rails (3.1.4) Installing uglifier (1.0.4) Your bundle is complete! Use `bundle show [gemname]` to see where a bundled gem is installed.


http://rubygems.org

http://rubygems.org

Rails Scaffolding$ jruby -S rails generate scaffold person name:string email:string invoke active_record create db/migrate/20111107052142_create_people.rb create app/models/person.rb⋮ create app/views/people/show.html.erb create app/views/people/new.html.erb create app/views/people/_form.html.erb invoke test_unit create test/functional/people_controller_test.rb invoke helper create app/helpers/people_helper.rb invoke test_unit create test/unit/helpers/people_helper_test.rb invoke assets invoke coffee create app/assets/javascripts/people.js.coffee invoke scss create app/assets/stylesheets/people.css.scss invoke scss create app/assets/stylesheets/scaffolds.css.scss


$ jruby -S rake db:migrate== CreatePeople: migrating ====================================-- create_table(:people) -> 0.0040s -> 0 rows== CreatePeople: migrated (0.0040s) ===========================

Migrate Database


$ jruby -S rails server=> Booting WEBrick=> Rails 3.1.1 application starting in development on http://0.0.0.0:3000=> Call with -d to detach=> Ctrl-C to shutdown server[2011-11-07 00:26:30] INFO WEBrick 1.3.1[2011-11-07 00:26:30] INFO ruby 1.8.7 (2011-11-05) [java][2011-11-07 00:26:30] INFO WEBrick::HTTPServer#start: pid=40454 port=3000

Start Server


http://0.0.0.0:3000

http://0.0.0.0:3000

http://0.0.0.0:3000

http://0.0.0.0:3000

First Page


app/controllers/people_controller.rbclass PeopleController < ApplicationController # GET /people # GET /people.json def index @people = Person.all

respond_to do |format| format.html # index.html.erb format.json { render :json => @people } end end⋮end


JSON out of the box


class Person < ActiveRecord::Baseend

app/models/person.rb


Rails Deployment


netbeans.org

Rails IDE and text editors

jetbrains.com/ruby/

redcareditor.com

•emacs•vi(m)•TextMate


http://netbeans.org

http://netbeans.org

http://www.jetbrains.com/ruby/




App

Requests

/vets/ Java/Spring

JRuby

/rack/

JRuby in Java web app


JRuby in Java web appdiff --git a/src/main/webapp/WEB-INF/web.xml b/src/main/webapp/WEB-INF/web.xmlindex 8d02684..60ed6cb 100644--- a/src/main/webapp/WEB-INF/web.xml+++ b/src/main/webapp/WEB-INF/web.xml@@ -87,6 +87,21 @@ <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener>++ <listener>+ <listener-class>org.jruby.rack.RackServletContextListener</listener-class>+ </listener>++ <servlet>+ <servlet-name>rack</servlet-name>+ <servlet-class>org.jruby.rack.RackServlet</servlet-class>+ </servlet>++ <servlet-mapping>+ <servlet-name>rack</servlet-name>+ <url-pattern>/rack/*</url-pattern>+ </servlet-mapping>+ <!-- Defines the 'default' servlet (usually for service static resources).


http://web.xml

http://web.xml

http://web.xml

http://web.xml

http://web.xml

http://web.xml

http://web.xml

http://web.xml

http://web.context.ContextLoaderListener

http://web.context.ContextLoaderListener

App

/vets /owners/ /owners/1/pets

Requests

Java/Spring

/vets/ JRuby

Rails in Java web app


Rails in Java web appdiff --git a/src/main/webapp/WEB-INF/web.xml b/src/main/webapp/WEB-INF/web.xmlindex 60ed6cb..f64b34d 100644--- a/src/main/webapp/WEB-INF/web.xml+++ b/src/main/webapp/WEB-INF/web.xml@@ -92,16 +92,6 @@ <listener-class>org.jruby.rack.RackServletContextListener</listener-class> </listener> - <servlet>- <servlet-name>rack</servlet-name>- <servlet-class>org.jruby.rack.RackServlet</servlet-class>- </servlet>-- <servlet-mapping>- <servlet-name>rack</servlet-name>- <url-pattern>/rack/*</url-pattern>- </servlet-mapping>- <!-- Defines the 'default' servlet (usually for service static resources).@@ -162,6 +152,16 @@ <url-pattern>/</url-pattern> </servlet-mapping> + <filter>+ <filter-name>RackFilter</filter-name>+ <filter-class>org.jruby.rack.RubyFirstRackFilter</filter-class>+ </filter>++ <filter-mapping>+ <filter-name>RackFilter</filter-name>+ <url-pattern>/*</url-pattern>+ </filter-mapping>+ <filter> <filter-name>httpMethodFilter</filter-name> <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>


http://web.xml

http://web.xml

http://web.xml

http://web.xml

http://web.xml

http://web.xml

http://web.xml

http://web.xml

http://web.filter.HiddenHttpMethodFilter

http://web.filter.HiddenHttpMethodFilter

More…

h0p://bit.ly/refactoring<to<railsh0p://vimeo.com/25410705


http://bit.ly/refactoring-to-rails

http://bit.ly/refactoring-to-rails

http://vimeo.com/25410705

http://vimeo.com/25410705

Testing LibrariesTest-Driven Development


Testing

25

50

75

100

Easy HardNum

ber o

f Tes

ts W

ritte

n (1

000'

s)

Ease of Writing Tests


$ jruby -S rails g scaffold person name:string email:string invoke active_record create db/migrate/20111107052142_create_people.rb create app/models/person.rb⋮ create app/views/people/show.html.erb create app/views/people/new.html.erb create app/views/people/_form.html.erb invoke test_unit create test/functional/people_controller_test.rb invoke helper create app/helpers/people_helper.rb invoke test_unit create test/unit/helpers/people_helper_test.rb invoke assets invoke coffee create app/assets/javascripts/people.js.coffee invoke scss create app/assets/stylesheets/people.css.scss invoke scss create app/assets/stylesheets/scaffolds.css.scss

Test files$ jruby -S rails g scaffold person name:string email:string invoke active_record create db/migrate/20111107052142_create_people.rb create app/models/person.rb⋮ create app/views/people/show.html.erb create app/views/people/new.html.erb create app/views/people/_form.html.erb invoke test_unit create test/functional/people_controller_test.rb invoke helper create app/helpers/people_helper.rb invoke test_unit create test/unit/helpers/people_helper_test.rb invoke assets invoke coffee create app/assets/javascripts/people.js.coffee invoke scss create app/assets/stylesheets/people.css.scss invoke scss create app/assets/stylesheets/scaffolds.css.scss


DeepThought.javaclass DeepThought { public static int answerToEverything(Object obj) { return 42; }

public static String getName() { return "DeepThought"; }}


RSpecrequire 'rspec'require 'java'

java_import 'DeepThought'

describe 'DeepThought' do describe '.answerToEverything' do it "should return 42, given any input" do DeepThought.answerToEverything(nil).should == 42 DeepThought.answerToEverything(true).should == 42 end end

describe '.getName' do it "should return 'DeepThought'" do DeepThought.name.should == "DeepThought" end endend


$ javac DeepThrought.java

$ jruby -rubygems deep_thought_spec.rb ..

Finished in 0.013 seconds2 examples, 0 failures

RSpec


Feature: AnswerToEverything Ask DeepThought the answer to everything

Scenario: Ask a question Given nil as input Then the result should be 42

Cucumber

Feature: getName Ask DeepThought what its name is

Scenario: get name When asked the name Then it answers the name as "DeepThought"


Cucumber$ jruby -S cucumberFeature: AnswerToEverything Ask DeepThought the answer to everything

Scenario: Ask a question # features/answer.feature:4 Given nil as input # features/step_definitions… Then the result should be 42 # features/step_definitions…

Feature: getName Ask DeepThought what its name is

Scenario: get name # features/… When asked the name # features/… Then it answers the name as "DeepThought" # features/…

2 scenarios (2 passed)4 steps (4 passed)0m0.065s


JTestr• Bridge for Java to make use of Ruby testing• Integrates with both Ant and Maven• Allows mocking of non-final Java class/method• Written by Ola Bini


JTestr Example

my_project/ build.xml! test/ test_hashmap.rb hashmap_spec.rb lib/ jtestr.jar src/ <your source ;) >


JTestr in Ant

<?xml version="1.0" encoding="UTF-8"?>

<project basedir="." default="jar" name="JRuby"> <target name="test" description="Runs all tests"> <taskdef name="jtestr" classname="org.jtestr.ant.JtestRAntRunner" classpath="lib/jtestr.jar"/> <jtestr/> </target></project>


Ruby’s test/unit

class HashMapTests < Test::Unit::TestCase def setup @map = java.util.HashMap.new end

def test_that_an_entry_can_be_added @map.put "foo", "bar" assert_equal "bar", @map.get("foo") end

def test_empty_key_set_iterator_throws_exception assert_raises(java.util.NoSuchElementException) do @map.key_set.iterator.next end endend

test/test_hashmap.rb


RSpec revisitedtest/hashmap_spec.rb

require 'java'java_import java.util.HashMap

describe "An empty", HashMap do before :each do @hash_map = java.util.HashMap.new end

it "should be able to add an entry to it" do @hash_map.put "foo", "bar" @hash_map.get("foo").should == "bar" end

it "should not be empty after an entry has been added to it" do @hash_map.put "foo", "bar" @hash_map.should_not be_empty end

it "should be empty" do @hash_map.should be_empty endend


Results

$ ant testBuildfile: /Users/asari/Development/projects/jtestr-example/build.xml

test: [jtestr] Other TestUnit: 2 tests, 0 failures, 0 errors [jtestr] [jtestr] Other Spec: 3 examples, 0 failures, 0 errors [jtestr] [jtestr] Total: 5 tests, 0 failures, 0 errors, 0 pending [jtestr]

BUILD SUCCESSFULTotal time: 7 seconds


Ant-Rake Integration


Problem…

dev.null

NUL

Windows

/dev/null

Un*x

dev_null

everything else


Ant…<condition property="dev.null" value="/dev/null"> <os family="unix"/></condition><condition property="dev.null" value="NUL"> <os family="windows"/></condition><condition property="dev.null" value="dev_null"> <not> <or> <os family="unix"/> <os family="windows"/> </or> </not></condition>


if os.family == 'unix' :dev_null = '/dev/null'elsif os.family == 'windows' :dev_null = 'NUL'else :dev_null = 'dev_null'end

Ruby


Ant…<macrodef name="run-junit-1.8-short"> <attribute name="compile.mode" default="OFF"/> <attribute name="jit.threshold" default="20"/> <attribute name="jit.maxsize" default="1000000000"/> <attribute name="reflection" default="false"/> <attribute name="thread.pooling" default="false"/> <attribute name="jvm.flags" default=""/>⋮</macrodef>⋮<target name="run-junit-compiled-short"> <run-junit-1.8-short compile.mode="JIT" jit.threshold="0"/></target>


Rubydef run_junit_18_short(opts={}) compile_mode = opts[:compile_mode] || 'OFF' jit_threshold = opts[:jit_threshold] || 20 jit_maxsize = opts[:jit_maxsize] || 1000000000 reflection = opts[:reflection] || false thread_pooling = opts[:thread_pooling] || false jvm_flags = opts[:jvm_flags] || "" ⋮end

def run_junit_compiled_short run_junit_18_short :compile_mode => 'JIT', :jit_threshold => 0end


Ant tasks from Rake<path id="build.classpath"> <fileset dir="${build.lib.dir}" includes="*.jar"/></path>

<path id="jruby.execute.classpath"> <path refid="build.classpath"/> <pathelement path="${jruby.classes.dir}"/></path>

task :initialize_paths do ant.path(:id => "build.classpath") do fileset :dir => BUILD_LIB_DIR, :includes => "*.jar" end

ant.path(:id => "jruby.execute.classpath") do path :refid => "build.classpath" pathelement :path => JRUBY_CLASSES_DIR endend


<project name="foobar" default="top-level" basedir="."> <description>Builds, tests, and runs foobar.</description>

<taskdef name="rakeimport" classname="org.jruby.ant.RakeImport"/> <rakeimport/>

<target name="top-level" depends="its_in_rake" />

<target name="its_in_ant"> <echo message="ant: its_in_ant"/> </target></project>

task :its_in_rake => [:setup, :its_in_ant] do puts "it's in Rake"end

task :setup do puts "setup in Rake"end

Rake tasks as Ant targets

build.xml

RakefileWednesday, November 16, 11








build.xml









RakefileWednesday, November 16, 11

Rake tasks as Ant targets<project name="foobar" default="top-level" basedir="."> <description>Builds, tests, and runs foobar.</description>













Rake tasks as Ant targetsBuildfile: build.xml[rakeimport] (in /tmp/example2)

setup:









setup:setup in Rake









setup:setup in Rake

its_in_ant:









setup:setup in Rake

its_in_ant: [echo] ant: its_in_ant









setup:setup in Rake


its_in_rake:









setup:setup in Rake


its_in_rake:it's in Rake









setup:setup in Rake


its_in_rake:it's in Rake

top-level:

BUILD SUCCESSFULTotal time: 7 seconds


More…

http://bit.ly/rake_ant




Maven and RubyGems


JRuby via Maven• Group ID: org.jruby• Artifact IDs: jruby, jruby-complete

<dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>3.8.1</version> <scope>test</scope> </dependency> <dependency> <groupId>org.jruby</groupId> <artifactId>jruby</artifactId> <version>1.6.5</version> </dependency></dependencies>


jruby -S gem install mvn:org.clojure:clojure

Maven artifacts as gems

maven



group ID




artifact ID



Successfully installed mvn:org.clojure:clojure-1.4.0.a.2-java1 gem installed


Some restrictions apply



Maven artifacts as gems$ jruby -S irbirb(main):001:0> require 'mvn:org.clojure:clojure'=> trueirb(main):002:0> java_import Java::clojure.lang.PersistentHashMap=> Java::ClojureLang::PersistentHashMapirb(main):003:0> phm = PersistentHashMap.create({:a => 100, :b => 200, :c => 300})=> {:c=>300, :a=>100, :b=>200}irb(main):004:0> phm.delete_if {|k,v| k == :b}Java::JavaLang::UnsupportedOperationException: from clojure.lang.APersistentMap.remove(APersistentMap.java:273) from org.jruby.java.proxies.MapJavaProxy$RubyHashMap.internalDelete(MapJavaProxy.java:154) from org.jruby.RubyHash.delete(RubyHash.java:1407) from org.jruby.RubyHash$22.visit(RubyHash.java:1464) from org.jruby.java.proxies.MapJavaProxy$RubyHashMap.visitAll(MapJavaProxy.java:182)⋮

$ jruby -S irbirb(main):001:0> require 'mvn:org.clojure:clojure'=> trueirb(main):002:0> java_import Java::clojure.lang.PersistentHashMap=> Java::ClojureLang::PersistentHashMapirb(main):003:0> phm = PersistentHashMap.create({:a => 100, :b => 200, :c => 300})=> {:c=>300, :a=>100, :b=>200}irb(main):004:0> phm.delete_if {|k,v| k == :b}Java::JavaLang::UnsupportedOperationException: from clojure.lang.APersistentMap.remove(APersistentMap.java:273) from org.jruby.java.proxies.MapJavaProxy$RubyHashMap.internalDelete(MapJavaProxy.java:154) from org.jruby.RubyHash.delete(RubyHash.java:1407) from org.jruby.RubyHash$22.visit(RubyHash.java:1464) from org.jruby.java.proxies.MapJavaProxy$RubyHashMap.visitAll(MapJavaProxy.java:182)⋮


Foreign Function Interface

Calling native functions


Gamma function

=∫ tz-1e-1 dt0

∞

Γ(z)


org.apache.commons.math.special Class Gammajava.lang.Object org.apache.commons.math.special.Gamma

public class Gammaextends java.lang.ObjectThis is a utility class that provides computation methods related to the Gamma family of functions.

Version:$Id: Gamma.java 1131229 2011-06-03 20:49:25Z luc $




Apache Commons?


http://commons.apache.org/math/apidocs/src-html/org/apache/commons/math/special/Gamma.html#line.29

http://commons.apache.org/math/apidocs/src-html/org/apache/commons/math/special/Gamma.html#line.29




Apache Commons?

License?

JAR

size


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Using a series transformation, Stirling-De Moivre asymptotic series ap-

proximation to the Gamma function is convertedinto a new one with better

convergence properties.

The new formula is compared with those of Stir-

ling, Laplace and Ramanujan for real arguments greaterthan 0.5 and turns

out to be, for equal number of ’correction’ terms, numerically

superior to

all of them. As a side benefit, a closed-form approximation has turned up

during the analysis which is about as good as 3rd order Stirling’s (maxi-

mum relative error smaller than 1e-10 for real arguments greater

or equal

to 10). Note: this articleis an extended version

of an older one [7] to which

it adds the estimate of the remainder.

1

I

n

t

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o

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t

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o

n

1

.

1

T

h

e

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In this paper, as we claimed in the abstract,we present a new asymptotic expansion for the

gamma function for real arguments greateror equal than one. We give an explicit formula

for the coe�cients in the seriesand estimate the error.

After the proof, we compared

our new formula with some classical results. The numerical

comparisonshows that for

equal number of ’correction’ terms the new formula is the most accurate and it is highly

recommended for computing the Gamma function for large real arguments.

T

h

e

o

r

e

m

1

.

Let x

� 1, then for every n

� 1, the following expression holds:

� (x) =

x

e

n

�1X

k

=0

G

k

x

2k

+ R

n

(x)

!!x

r 2⇡x

,

(1.1)

where R

n

(x) = O� 1

x

2n

� and the G

k

coe�cients are given by

G

k

=

X

m

1,m2,..

.

,

m

k�0

2m

1+4m

2+.

.

.

+2k

m

k=2k

kY

r

=1

1m

r

!

✓B

2r

2r (2r � 1)

◆m

r

,

G

0 = 1,(1.2)

where B

r

denotes the r

t

h Bernoulli number [4]. Moreover, if x

� n

+ 1, then

|Rn

(x)|

(n + 1) e

+8e1

/

5

n

(2n� 1) (2⇡)2n

! ⇣n

x

⌘2n

.

(1.3)

1n

e

m

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1

Read academic paper

New asymptotic expansion for the � (x) function

Gergo Nemes

1

December 7, 2008

http://dx.doi.org/10.3247/sl2math08.005

Abstract

Using a series transformation, Stirling-De Moivre asymptotic series ap-proximation to the Gamma function is converted into a new one with betterconvergence properties. The new formula is compared with those of Stir-ling, Laplace and Ramanujan for real arguments greater than 0.5 and turnsout to be, for equal number of ’correction’ terms, numerically superior toall of them. As a side benefit, a closed-form approximation has turned upduring the analysis which is about as good as 3rd order Stirling’s (maxi-mum relative error smaller than 1e-10 for real arguments greater or equalto 10). Note: this article is an extended version of an older one [7] to whichit adds the estimate of the remainder.

1 Introduction

1.1 The main result

In this paper, as we claimed in the abstract, we present a new asymptotic expansion for thegamma function for real arguments greater or equal than one. We give an explicit formulafor the coe�cients in the series and estimate the error. After the proof, we comparedour new formula with some classical results. The numerical comparison shows that forequal number of ’correction’ terms the new formula is the most accurate and it is highlyrecommended for computing the Gamma function for large real arguments.

Theorem 1. Let x � 1, then for every n � 1, the following expression holds:

� (x) =

x

e

n�1X

k=0

G

k

x

2k

+ R

n

(x)

!!x

r2⇡

x

, (1.1)

where R

n

(x) = O � 1x

2n

�and the G

k

coe�cients are given by

G

k

=X

m1,m2,...,mk�02m1+4m2+...+2kmk=2k

kY

r=1

1m

r

!

✓B2r

2r (2r � 1)

◆mr

, G0 = 1, (1.2)

where B

r

denotes the r

th Bernoulli number [4]. Moreover, if x � n + 1, then

|Rn

(x)|

(n + 1) e +8e

1/5

n (2n� 1) (2⇡)2n

!⇣n

x

⌘2n

. (1.3)

[email protected]

1


}

if (Double.isNaN(x)) { value = Double.NaN; return; }

double int_part = (int) x; sign = (int_part % 2 == 0 && (x - int_part) != 0.0 && (x < 0)) ? -1 : 1; if ((x - int_part) == 0.0 && 0 < int_part && int_part <= FACTORIAL.length) { value = Math.log(FACTORIAL[(int) int_part - 1]); } else if (x < 10) { double rising_factorial = 1; for (int i = 0; i < (int) Math.abs(x) - int_part + 10; i++) { rising_factorial *= (x + i); } NemesLogGamma l = new NemesLogGamma(x + (int) Math.abs(x) - int_part value = l.value - Math.log(Math.abs(rising_factorial)); } else { double temp = 0.0; for (int i = 0; i < NEMES_GAMMA_COEFF.length; i++) { temp += NEMES_GAMMA_COEFF[i] * 1.0 / Math.pow(x, i); }

value = x * (Math.log(x) - 1 + Math.log(temp)) + (Math.log(2) + Math.log(Math.PI) - Math.log(x)) / 2.0; }

…and implement

Hard!


man gamma

man…


Not reinventing the wheel

TGAMMA(3) BSD Library Functions Manual TGAMMA(3)

NAME tgamma, lgamma, gamma -- gamma and log of gamma

SYNOPSIS #include <math.h>

double tgamma(double x);⋮

DESCRIPTION tgamma() calculates the gamma function of x. lgamma() calculates the natural logorithm of the absolute value of the gamma function of x. gamma() is the same function as tgamma. Its use is deprecated.

⋮


$ java Example

Example.class

javac

JNI Workflow

Example.java Example.hjavah

gamma.c libgamma.dylibcc


import java.util.*;

class Example { native static double gamma(double x);

static { System.loadLibrary("gamma"); }

public static void main(String args[]) { System.out.println(gamma(0.5)); }}

Example.java


/* DO NOT EDIT THIS FILE - it is machine generated */#include <jni.h>/* Header for class Example */

#ifndef _Included_Example#define _Included_Example#ifdef __cplusplusextern "C" {#endif/* * Class: Example * Method: gamma * Signature: (D)D */JNIEXPORT jdouble JNICALL Java_Example_gamma (JNIEnv *, jclass, jdouble);

#ifdef __cplusplus}#endif#endif

Example.h


#include "Example.h"#include <math.h>

JNIEXPORT jdouble JNICALL Java_Example_gamma(JNIEnv* env,jclass jclass, jdouble jdbl) { return tgamma(jdbl);}

gamma.c


$ javah Example.java$ javac Example.java$ gcc -shared gamma.c -o libgamma.dylib \ -I /Library/Java/JavaVirtualMachines/1.6.0_29-b11-397.jdk/Contents/Headers/

$ java Example1.772453850905516

Voilà!


require 'ffi'

module Gamma extend FFI::Library ffi_lib FFI::Library::LIBC attach_function :tgamma, [:double], :doubleend

puts Gamma::tgamma(0.5)

gamma.rb


Same result*!$ jruby gamma.rb 1.77245385090552

$ jruby --1.9 -e 'p Math::gamma(0.5)'1.77245385090552


Benchmark$ jruby --1.9 bench_gamma.rb Rehearsal ----------------------------------------------------------------pure_java 3.432000 0.000000 3.432000 ( 3.432000)JNI 0.409000 0.000000 0.409000 ( 0.409000)FFI 0.281000 0.000000 0.281000 ( 0.281000)-------------------------------------------------------- total: 4.122000sec

user system total realpure_java 2.849000 0.000000 2.849000 ( 2.849000)JNI 0.288000 0.000000 0.288000 ( 0.289000)FFI 0.219000 0.000000 0.219000 ( 0.219000)


But…

What ab

out Indy?

h0p://www.flickr.com/photos/evablue/5665409533/


http://www.flickr.com/photos/evablue/5665409533/

http://www.flickr.com/photos/evablue/5665409533/

Invokedynamic!• Only mainstream

alternative JVM language• Worked closely with

Hotspot team• JRuby master/1.7• Waiting for Java 1.7.0u2

release• What does it mean for

you?


0

4

8

12

16

fib +calls +consts +both richardsredblack

1.9x3.2x

7.4x

14.2x

3.6x

5.5x

1.6x1.8x

3.5x4.4x

1.7x2.7x

Times faster than Ruby 1.9.3

JRuby on Java 6JRuby on invokedynamic

Benchmark


0

0.075

0.150

0.225

0.300

currentTimeMillis Thread#name

Benchmark

No indy With indyWednesday, November 16, 11

Indy TODOs• Remaining invocation paths

–varargs, super, all Java paths• Per-type specialization

–Faster block-receiving calls–Faster module methods

• More code in Ruby!


Thank you!• Twitter: @hiro_asari• Github: BanzaiMan

– Code examples:• jtestr-example • jni-gamma• test_example_deepthought• http://github.com/jruby/jruby

http://www.engineyard.com/tryjrubyWednesday, November 16, 11

https://github.com/BanzaiMan/jtestr-example

https://github.com/BanzaiMan/jtestr-example

https://github.com/BanzaiMan/jni-gamma

https://github.com/BanzaiMan/jni-gamma

https://github.com/BanzaiMan/test_example_deepthought

https://github.com/BanzaiMan/test_example_deepthought

http://github.com/jruby/jruby

http://github.com/jruby/jruby

http://www.engineyard.com/tryjruby

http://www.engineyard.com/tryjruby

References• http://ruby-lang.org• http://jruby.org• http://pragprog.com/book/jruby/using-jruby• http://rubyonrails.org• http://torquebox.org• http://tomcat.apache.org• http://jetty.codehause.org• http://glassfish.java.net• https://www.relishapp.com/rspec• http://cukes.info


http://ruby-lang.org

http://ruby-lang.org

http://jruby.org

http://jruby.org

http://pragprog.com/book/jruby/using-jruby

http://pragprog.com/book/jruby/using-jruby

http://rubyonrails.org

http://rubyonrails.org

http://torquebox.org

http://torquebox.org

http://tomcat.apache.org

http://tomcat.apache.org

http://jetty.codehaus.org

http://jetty.codehaus.org

http://glassfish.java.net

http://glassfish.java.net

https://www.relishapp.com/rspec

https://www.relishapp.com/rspec

http://cukes.info/

http://cukes.info/

References• http://jtestr.codehaus.org/• http://www.ebyte.it/library/docs/math07/

GammaApproximation.html• http://download.oracle.com/javase/6/docs/

technotes/guides/jni/• http://jcp.org/en/jsr/detail?id=292


http://jtestr.codehaus.org/

http://jtestr.codehaus.org/

http://www.ebyte.it/library/docs/math07/GammaApproximation.html




http://download.oracle.com/javase/6/docs/technotes/guides/jni/




http://jcp.org/en/jsr/detail?id=292

http://jcp.org/en/jsr/detail?id=292

jruby: enhancing java developers' lives

Technology

radius public circleint

radius public int getradius

public double getarea

easy public class circle

thing public class circle

value public class circle

classes public class

mandatory public class