Plans for X10 2'0

1
Plans for X10 2.0

• Nate Nystrom
• IBM

2
Outline

• Polyglot 3 done
• X10 1.7 built on P3 August
• X10 2.0 2009

3
Polyglot 3
4
Motivation

• Pass scheduler in P2 was a disaster
• Difficult to use and debug, infinite loops
• Main goal of P3 is to fix the pass scheduler
• Also cleans up type system code
• Not backward compatible with P2

5
Changes vs. P2

• Pass scheduling
• Lazy references
• Type system interface
• Lots of little changes

6
Pass scheduling

• Passes can now run on AST fragments
• Simplifies checking of dependent types
• e.g., to compute type of Field e.f, may run pass
  just on the FieldDecl T f to resolve the type T

7
Lazy references

• Added level of indirection for references to type
  system objects
• class LazyRefltTgt implements RefltTgt
• T get() ... run pass to compute result if
  needed... ...
• interface MethodDef
• RefltTypegt returnType()
• ListltRefltTypegtgt formalTypes() ...

8
Type system changes

• Split type objects into Uses and Defs
• class FieldInstance implements UseltFieldDefgt
• Type type() if (type null) type
  def.type() return type ...
• Helps with dependent types and generics
  implementations
• Can apply substitutions to Use without affecting
  Def

9
X10 2.0
10
X10 2.0 Features

• Scala-like syntax
• Generics
• Closures
• Type inference
• Redesigned core type system
• value types, arrays, regions, clocks, ...

11
X10 1.7

• Scala-like syntax (partial)
• Generics
• Closures
• Type inference (partial)
• Redesigned core type system
• value types, arrays, regions, clocks, ...

12
Syntax changes
13
Closures

• (x Int, y Int) Int gt xy
• x Boolean gt x
• () gt new C()
• gt if (G) return new C() else throw E

14
Operators

• Can use operators as functions
• Int., Int.-, Int., ...
• Boolean., Boolean.!, ...

15
Methods as functions

• class C
• def m(x T) ...
• f C.m.(T) f(y)

16
Function types

• (Int, Int) gt Int
• (a ArrayDouble,
• r Regiona.region.contains(self))
• gt ArrayDoubleregionr
• x Int gt Intselfx

17
Array initializers

• new doubled 0
• ? new ArrayDouble(d, gt 0)
• new doubled (p point) Bp
• ? new ArrayDouble(d, p point(d) gt B(p))

18
Futures

• future (p) S
• ? future (p, gt S )

19
Generics in X10
20
Constrained types

• Types have properties (public final fields)
• class Region(rank Int, ...)
• Ce
• type of all instances of class C such that e is
  true
• e.g., Regionrank2

21
Type properties

• Generalize to type properties
• class ListT def get(i Int) T
• Type properties are instance members
• e.T is a type

22
Generic types

• Constrain the type properties
• ListTC sugar ListC
• ListTltC sugar ListC
• ListTgtC sugar List-C

23
Generic functions

• Add type parameters to methods
• class ListT
• def mapS(f T gt S) ListS
• ys ListS new ListS()
• for (x T in this) ys.add(f(x))
• return ys

24
Where clauses

• class ListT
• def appendS(x S)TltS ListS

25
Structural constraints

• X has var x T
• X has a field
• X has def m(T) U
• X has a method
• X has def this(T) U
• X has a constructor

26
Array

• class ArrayT(dist Dist, ...)
• def get(p Point(dist.region)) ...
• def add(a ArrayT(dist))T has def
  add(T,T)T
• new ArrayT(dist, pgtthis(p)a(p))

27
Translation

• Translate to template class
• Type properties represented as run-time type
  object (rtt)
• class ListT def get(i Int) T ... ...
• ? class List rtt T class T // dummy class
• T get(int i) ... ...

28
Template instantiation

• Load bytecode for List and instantiate
• class ListDouble
• rtt T
• double get(int i) ...
• Need rtt to implement casts, instanceof for
  dependent types

29
Instanceof

• Need rtt to implement casts, instanceof for
  dependent types
• class ListDouble
• rtt T ...
• boolean instanceof(Object o)
• return o instanceof ListDouble
• ((ListDouble) o).T).equals(T)

30
Object instantiation

• new ListDoubleselfgt0()
• ?
• new ListDouble(Double.getRTT(selfgt0))
• Need run-time representation of constraints to
  implement casts, instanceof

31
Performance

• one class instantiation per X10 class
• one rtt object per X10 type

32
Type defs

• type StringSet SetString
• type StringMapT MapString,T
• type Int(x Int) Intselfx
• type Int(x Int, y Int) Intxltself,selflty