Presented at the NLJUG Java 7 launch event 7/7/2011

1. Java 7 Launch
Fork/Join concurrency
@Sander_Mak

2. What?
Fork:
Recursively decompose
large task into subtasks
Join:
Combine results of
recursive tasks
7/7/2011 Java 7 Launch Event

3. Why?
Mul3core challenge
7/7/2011 Java 7 Launch Event

4. How?
Introducing:
java.uLl.concurrent.ForkJoinPool Worker 1
• ‘ExecutorService with Worker 2
runLme tuning’
• Recursive algorithms
Worker 3
• Workstealing
7/7/2011 Java 7 Launch Event

5. ... MapReduce?
Environment Single JVM Cluster
Model Recursive forking Single fork step
Scales with Cores/CPUs Nodes
Opera3on Workstealing No inter‐node
communicaLon
7/7/2011 Java 7 Launch Event

6. Example
Sony’s been hacked...
Are we compromised...?
7/7/2011 Java 7 Launch Event

7. Java 7 Launch
JSR‐292: Invokedynamic
@Sander_Mak

8. JVM Languages
Java
7/7/2011 Java 7 Launch Event

9. JVM Languages
Groovy Clojure
JRuby Java JavaFX
Scala
7/7/2011 Java 7 Launch Event

10. JVM Languages
jProlog Pizza MultiJava
Fantom
JLog
Groovy Clojure MetaJ
JRuby Java JavaFX Jaskell
Rhino Scala JBasic
Aardappel
Funnel
Jacl Drools
Jython
7/7/2011 Java 7 Launch Event

11. JVM Languages
Hundreds of
Languages
7/7/2011 Java 7 Launch Event

12. JVM Languages
‘Language ficLons’
JVM
Exceptions
Primitive types
Objects
Access control
Garbage coll.
Threading
Memory model
7/7/2011 Java 7 Launch Event

13. JVM Languages
‘Language ficLons’
Java
Enums
Checked exc.
JVM Generics
Exceptions Exceptions
Primitive types Primitive types
Objects Objects
Access control Access control
Garbage coll. Garbage coll.
Threading Threading.
Memory model Memory model
7/7/2011 Java 7 Launch Event

14. JVM Languages
JRuby
‘Language ficLons’ Open classes
Dynamic typing
Java Closures
Enums Enums
Checked exc. Checked exc.
JVM Generics Generics
Exceptions Exceptions Exceptions
Primitive types Primitive types Primitive types
Objects Objects Objects
Access control Access control Access control
Garbage coll. Garbage coll. Garbage coll.
Threading Threading. Threading
Memory model Memory model Memory model
7/7/2011 Java 7 Launch Event

15. JVM Languages
JRuby
‘Language ficLons’ Open classes
Dynamic typing
Java Closures
Enums Enums
Checked exc. Checked exc.
JVM Generics Generics
Exceptions Exceptions Exceptions
Primitive types Primitive types Primitive types
Objects Objects Objects
Access control Access control Access control
Garbage coll. Garbage coll. Garbage coll.
Threading Threading. Threading
Memory model Memory model Memory model
7/7/2011 Java 7 Launch Event

16. JVM Languages
Obviously JVM is viable, however:
• Language implementors need to invent
‘creaLve’ compilaLon schemes for every
language
• Performance suffers when abstracLng beyond
Java idioms
How to improve?
7/7/2011 Java 7 Launch Event

17. JSR‐292
Mission:
“We are extending the JVM with first-class architectural
support for languages other than Java, especially dynamic
languages. This project will prototype a number of
extensions to the JVM, so that it can run non-Java languages
efficiently, with a performance level comparable to that of
Java itself.” http://openjdk.java.net/projects/mlvm/
7/7/2011 Java 7 Launch Event

18. Compiling dynamic languages
• JVM pre]y language‐friendly
• ExcepLon: method calls
– Signature at callsite must match exactly
TargetClass Name Method descriptor
18:
invokevirtual
#5; //Method java/util/ArrayList.add:(Ljava/lang/Object;)Z
– Dispatch on staLc type of parameters and dynamic
type of receiver
– Method must exist at compile Lme
– Link to target is fixed, no relinking
7/7/2011 Java 7 Launch Event

19. Compiling dynamic languages
• Common soluLons:
- Don’t compile, interpret (someLmes unavoidable)
- Introduce generic CallSite abstracLon which dispatches
method calls
- AOT compilaLon into specialized invoker classes
(suitable for core methods)
- JIT bytecode generaLon of small stub methods
Either way: abundance of syntheLc types and
bytecode hard to opLmize for JVM
7/7/2011 Java 7 Launch Event

20. Invokedynamic
New bytecode, last piece of JSR‐292 puzzle:
Name Method descriptor
18:
invokedynamic
#5; //NameAndType addInts:(II)I
• InvocaLon without reference to actual method
descriptor
• Instead, symbolic name and type
• No receiver: all arguments are equal
What is the target?
7/7/2011 Java 7 Launch Event

21. Method handles
• Lightweight, safe method pointers
• Like java.lang.reflect.Method, but:
– No argument boxing/unboxing
– Access checks only at creaLon Lme
– Leaner, can be as fast as direct call
– No wrapping of excepLons
7/7/2011 Java 7 Launch Event

22. Method handles
• Lightweight, safe method pointers
• Like java.lang.reflect.Method, but:
– No argument boxing/unboxing
– Access checks only at creaLon Lme
– Leaner, can be as fast as direct call
– No wrapping of excepLons
Java 7
MethodHandle mh =
MethodHandles.lookup().findVirtual(String.class,
“substring”, typeDescriptor);
String java = (String) mh.invokeExact(“jjava”, 1);
7/7/2011 Java 7 Launch Event

23. Invokedynamic ‐ bootstrap
• Invokedynamic triggers bootstrap
• Ader installing target, invokedynamic invokes
MH directly
DynamicInvokerClass ImplementationClass
aload_1;
invokedyn. meth:Type; implementation(Type) {
return; result = ..
return result
}
bootstrap( .. ) {
..lookup..
return CallSite
}
7/7/2011 Java 7 Launch Event

24. Invokedynamic ‐ bootstrap
• Invokedynamic triggers bootstrap
• Ader installing target, invokedynamic invokes
MH directly
DynamicInvokerClass ImplementationClass
aload_1;
invokedyn. meth:Type; implementation(Type) {
return; result = ..
return result
}
bootstrap( .. ) {
..lookup..
return CallSite
}
7/7/2011 Java 7 Launch Event

25. Invokedynamic ‐ bootstrap
• Invokedynamic triggers bootstrap
• Ader installing target, invokedynamic invokes
MH directly
DynamicInvokerClass ImplementationClass
aload_1;
invokedyn. meth:Type; implementation(Type) {
return; result = ..
return result
}
bootstrap( .. ) {
..lookup..
return CallSite
}
7/7/2011 Java 7 Launch Event

26. Invokedynamic ‐ bootstrap
• Invokedynamic triggers bootstrap
• Ader installing target, invokedynamic invokes
MH directly
DynamicInvokerClass ImplementationClass
aload_1;
invokedyn. meth:Type; implementation(Type) {
return; result = ..
return result
}
bootstrap( .. ) {
..lookup.. MH can be guarded
return CallSite
with test, adapt types,
} etc.
7/7/2011 Java 7 Launch Event

27. Invokedynamic ‐ bootstrap
• Invokedynamic triggers bootstrap
• Ader installing target, invokedynamic invokes
MH directly
DynamicInvokerClass ImplementationClass
aload_1;
invokedyn. meth:Type; Method implementation(Type) {
return; Handle(s) result = ..
return result
}
bootstrap( .. ) {
..lookup..
return CallSite
}
7/7/2011 Java 7 Launch Event

28. Invokedynamic
• Invokedynamic + bootstrap method allow
language to up‐call from VM for linking/
dispatching.
Not impossible before, but hard and slow. JVM now
fully opLmizes dynamic calls.
7/7/2011 Java 7 Launch Event

29. Wrap‐up
• JSR‐292 invokedynamic features:
– Let’s language implementors avoid tricks
– Level the playing ground, speedwise
– Allow exisLng VM opLmizaLons to be applied to
new paradigms
• JRuby, Groovy acLvely working on JSR‐292
support
• For example, JRuby can cut 80% of linking/
calling code in runLme
7/7/2011 Java 7 Launch Event

30. Java 7 Launch
Beyond Java 7
@Sander_Mak

31. Ader JDK7
7/7/2011 Java 7 Launch Event

32. JDK8: Coin conLnued
Java 7
List<Integer> piDigits = Collections.unmodifiableList
(Arrays.asList(3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 9 ));
Java 8
// List literal:
List<Integer> piDigits = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 9];
Integer first = piDigits[0];
// Map literal:
Map<Integer, String> platonicSolids = { 4 : "tetrahedron",
6 : "cube", 8 : "octahedron", 12 : "dodecahedron",
20 : "icosahedron"
};
7/7/2011 Java 7 Launch Event

33. JDK8: Project Lambda
• Add first‐class funcLons
• Single Abstract Method types
• Solve interface evoluLon with ‘defender
methods’
• Paves way for parallel collecLons
Java 8
// Lambda expression
List<Integer> list = [1,2,3];
list.forEach(#{ e -> e * 2; });
// Reference existing methods
Person[] people = ...
Arrays.sort(people, #Person.compareByAge);
7/7/2011 Java 7 Launch Event

34. JDK8: Modularity
JSR‐294 ‘Project Jigsaw’, goals:
• Modular JDK
- SE Core
- Packages: Swing, CORBA, XML, etc.
• Modular and versioned applicaLons
• Integrate with plamorm dependency
management
7/7/2011 Java 7 Launch Event

35. JDK8
Available Fall/Winter of
See you @ next launch event?
7/7/2011 Java 7 Launch Event