What do auto(un)boxing, specialization and value classes have in common?

Late Data Layout presentation at the Scala Bay Area Meetup (thanks Vlad Patryshev!): What do auto(un)boxing, specialization and value classes have in common?

The recording is available on youtube:
https://www.youtube.com/watch?v=HPqNmaAUAJc

Project website: http://scala-miniboxing.org

Transcript

1. scala-miniboxing.org 1st of August 2014
   Scala Bay Area Meetup
   Linkedin HQ, Mountain View
   

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2. scala-miniboxing.org
   Vlad URECHE
   PhD student in the Scala Team @ EPFL
   Miniboxing guy. Also worked on
   specialization, the backend and scaladoc.
   @
   @VladUreche
   @VladUreche
   vlad.ureche@gmail.com
   

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3. scala-miniboxing.org
   What do auto(un)boxing,
   specialization and value
   classes have in common?
   

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4. scala-miniboxing.org
   What do auto(un)boxing,
   specialization and value
   classes have in common?
   What are they?
   

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5. 5
   scala-miniboxing.org
   Auto(un)boxing
   Auto(un)boxing
   def identity[T](t: T): T = t
   

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6. 6
   scala-miniboxing.org
   Auto(un)boxing
   Auto(un)boxing
   def identity[T](t: T): T = t
   scalac / javac
   

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7. 7
   scala-miniboxing.org
   Auto(un)boxing
   Auto(un)boxing
   def identity[T](t: T): T = t
   def identity(t: Object): Object = t
   scalac / javac
   

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8. 8
   scala-miniboxing.org
   Auto(un)boxing
   Auto(un)boxing
   def identity[T](t: T): T = t
   def identity(t: Object): Object = t
   The process is called erasure,
   and is the simplest translation
   of generics to bytecode.
   scalac / javac
   

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9. 9
   scala-miniboxing.org
   Auto(un)boxing
   Auto(un)boxing
   identity(5)
   

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10. 10
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    identity(5)
    scalac / javac
    

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11. 11
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    identity(5)
    identity(j.l.Integer.valueOf(5)).intValue
    scalac / javac
    

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12. 12
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    identity(5)
    identity(j.l.Integer.valueOf(5)).intValue
    scalac / javac
    Object representation
    

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13. 13
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    identity(5)
    identity(j.l.Integer.valueOf(5)).intValue
    scalac / javac inflates heap
    requirements
    Object representation
    

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14. 14
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    identity(5)
    identity(j.l.Integer.valueOf(5)).intValue
    scalac / javac produces
    garbage
    inflates heap
    requirements
    Object representation
    

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15. 15
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    identity(5)
    identity(j.l.Integer.valueOf(5)).intValue
    scalac / javac produces
    garbage
    inflates heap
    requirements
    indirect
    (slow) access
    to the value
    Object representation
    

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16. 16
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    identity(5)
    identity(j.l.Integer.valueOf(5)).intValue
    scalac / javac produces
    garbage
    breaks locality
    guarantees
    inflates heap
    requirements
    indirect
    (slow) access
    to the value
    Object representation
    

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17. 17
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = 5
    

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18. 18
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = 5
    scala.Int behaves like an object
    (has methods, can be used with generics)
    

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19. 19
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = 5
    scalac
    scala.Int behaves like an object
    (has methods, can be used with generics)
    

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20. 20
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = 5
    val five: int = 5
    scalac
    scala.Int behaves like an object
    (has methods, can be used with generics)
    

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21. 21
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = 5
    val five: int = 5
    scalac
    Unboxed integer
    scala.Int behaves like an object
    (has methods, can be used with generics)
    

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22. 22
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = 5
    val five: int = 5
    scalac
    Unboxed integer
    five + 3
    scala.Int behaves like an object
    (has methods, can be used with generics)
    

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23. 23
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = 5
    val five: int = 5
    scalac
    Unboxed integer
    five + 3
    scalac
    scala.Int behaves like an object
    (has methods, can be used with generics)
    

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24. 24
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = 5
    val five: int = 5
    scalac
    Unboxed integer
    five + 3
    five + 3
    scalac
    scala.Int behaves like an object
    (has methods, can be used with generics)
    

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25. 25
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = 5
    val five: int = 5
    scalac
    Unboxed integer
    five + 3
    five + 3
    scalac
    Unboxed addition
    scala.Int behaves like an object
    (has methods, can be used with generics)
    

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26. 26
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = identity(5)
    

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27. 27
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = identity(5)
    scalac
    

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28. 28
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = identity(5)
    val five: int =
    scalac
    

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29. 29
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = identity(5)
    val five: int =
    identity(I.valueOf(5)).intValue
    scalac
    

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30. 30
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = identity(5)
    val five: int =
    identity(I.valueOf(5)).intValue
    scalac
    Boxing coercion
    

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31. 31
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    val five: Int = identity(5)
    val five: int =
    identity(I.valueOf(5)).intValue
    scalac
    Boxing coercion Unboxing coercion
    

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32. 32
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    scala.Int
    

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33. 33
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    scala.Int
    

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34. 34
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    scala.Int
    int
    ●
    fast access
    ●
    no garbage collection
    ●
    locality
    

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35. 35
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    scala.Int
    int
    ●
    fast access
    ●
    no garbage collection
    ●
    locality
    ●
    indirect access
    ●
    object allocation
    ●
    and thus garbage collection
    ●
    no locality guarantees
    ●
    compatible with erased generics
    java.lang.Integer
    

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36. 36
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    scala.Int
    int
    ●
    fast access
    ●
    no garbage collection
    ●
    locality
    ●
    indirect access
    ●
    object allocation
    ●
    and thus garbage collection
    ●
    no locality guarantees
    ●
    compatible with erased generics
    java.lang.Integer
    incompatible
    → coercions
    

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37. scala-miniboxing.org
    What do auto(un)boxing,
    specialization and value
    classes have in common?
    

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38. 38
    scala-miniboxing.org
    Specialization
    Specialization
    def identity[T](t: T): T = t
    

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39. 39
    scala-miniboxing.org
    Specialization
    Specialization
    def identity[T](t: T): T = t
    specialization
    

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40. 40
    scala-miniboxing.org
    Specialization
    Specialization
    def identity[T](t: T): T = t
    def identity(t: Object): Object = t
    specialization
    

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41. 41
    scala-miniboxing.org
    Specialization
    Specialization
    def identity[T](t: T): T = t
    def identity(t: Object): Object = t
    specialization
    def identity_Z(t: bool): bool = t
    

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42. 42
    scala-miniboxing.org
    Specialization
    Specialization
    def identity[T](t: T): T = t
    def identity(t: Object): Object = t
    specialization
    def identity_Z(t: bool): bool = t
    def identity_C(t: char): char = t
    

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43. 43
    scala-miniboxing.org
    Specialization
    Specialization
    def identity[T](t: T): T = t
    def identity(t: Object): Object = t
    specialization
    def identity_Z(t: bool): bool = t
    def identity_C(t: char): char = t
    … (7 other variants)
    

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44. 44
    scala-miniboxing.org
    Specialization
    Specialization
    identity(5)
    

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45. 45
    scala-miniboxing.org
    Specialization
    Specialization
    identity(5)
    specialization
    

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46. 46
    scala-miniboxing.org
    Specialization
    Specialization
    identity(5)
    identity_I(5)
    specialization
    

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47. 47
    scala-miniboxing.org
    Specialization
    Specialization
    identity(5)
    identity_I(5)
    specialization
    The variant of identity
    specialized for int
    

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48. 48
    scala-miniboxing.org
    Specialization
    Specialization
    identity(5)
    identity_I(5)
    specialization
    The variant of identity
    specialized for int
    // no boxing!
    

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49. 49
    scala-miniboxing.org
    Specialization
    Specialization
    def tupled[T1, T2](t1: T1, t2: T2) ...
    

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50. 50
    scala-miniboxing.org
    Specialization
    Specialization
    def tupled[T1, T2](t1: T1, t2: T2) ...
    specialization
    

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51. 51
    scala-miniboxing.org
    Specialization
    Specialization
    def tupled[T1, T2](t1: T1, t2: T2) ...
    // 100 methods (102)
    specialization
    

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52. 52
    scala-miniboxing.org
    Specialization
    Specialization
    def tupled[T1, T2](t1: T1, t2: T2) ...
    // 100 methods (102)
    specialization
    

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53. 53
    scala-miniboxing.org
    Specialization
    Specialization
    def tupled[T1, T2](t1: T1, t2: T2) ...
    // 100 methods (102)
    specialization
    Can we do something
    about this?
    

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54. 54
    scala-miniboxing.org
    Specialization
    Specialization
    def tupled[T1, T2](t1: T1, t2: T2) ...
    // 100 methods (102)
    specialization
    Can we do something
    about this?
    

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55. 55
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    def identity[T](t: T): T = t
    

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56. 56
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    def identity[T](t: T): T = t
    miniboxing
    

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57. 57
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    def identity[T](t: T): T = t
    def identity(t: Object): Object = t
    miniboxing
    

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58. 58
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    def identity[T](t: T): T = t
    def identity(t: Object): Object = t
    miniboxing
    def identity_M(..., t: long): long = t
    

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59. 59
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    def identity[T](t: T): T = t
    def identity(t: Object): Object = t
    miniboxing
    def identity_M(..., t: long): long = t
    long encodes all
    primitive types
    

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60. 60
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    def identity[T](t: T): T = t
    def identity(t: Object): Object = t
    miniboxing
    def identity_M(..., t: long): long = t
    Only 2n variants
    long encodes all
    primitive types
    

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61. 61
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    identity(3)
    

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62. 62
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    identity(3)
    miniboxing
    

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63. 63
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    identity(3)
    identity_M(..., int2minibox(3))
    miniboxing
    

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64. 64
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    identity(3)
    identity_M(..., int2minibox(3))
    miniboxing
    Coercion
    

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65. 65
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    identity(3)
    identity_M(..., int2minibox(3))
    miniboxing
    Coercion
    The miniboxed
    variant of identity
    

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66. 66
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    T
    

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67. 67
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    T
    

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68. 68
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    T
    long
    ●
    preferred encoding
    

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69. 69
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    T
    long
    ●
    preferred encoding ●
    fallback encoding
    ●
    compatible with
    ●
    method calls
    ●
    supertypes
    ●
    erased generics
    T (erased to Object)
    

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70. 70
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    T
    long
    ●
    preferred encoding ●
    fallback encoding
    ●
    compatible with
    ●
    method calls
    ●
    supertypes
    ●
    erased generics
    T (erased to Object)
    incompatible
    → coercions
    

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71. scala-miniboxing.org
    What do auto(un)boxing,
    specialization and value
    classes have in common?
    

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72. 72
    scala-miniboxing.org
    Value Classes
    Value Classes
    def abs(c: Complex): Double = ...
    

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73. 73
    scala-miniboxing.org
    Value Classes
    Value Classes
    def abs(c: Complex): Double = ...
    value class transformation
    

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74. 74
    scala-miniboxing.org
    Value Classes
    Value Classes
    def abs(c: Complex): Double = ...
    def abs(c_re: Double,
    c_im: Double): Double = ...
    value class transformation
    

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75. 75
    scala-miniboxing.org
    Value Classes
    Value Classes
    def abs(c: Complex): Double = ...
    def abs(c_re: Double,
    c_im: Double): Double = ...
    value class transformation
    No object created!
    

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76. 76
    scala-miniboxing.org
    Value Classes
    Value Classes
    val c: Complex = Complex(2,1)
    

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77. 77
    scala-miniboxing.org
    Value Classes
    Value Classes
    val c: Complex = Complex(2,1)
    value class transformation
    

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78. 78
    scala-miniboxing.org
    Value Classes
    Value Classes
    val c: Complex = Complex(2,1)
    val c_re: Double = 2
    val c_im: Double = 1
    value class transformation
    

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79. 79
    scala-miniboxing.org
    Value Classes
    Value Classes
    val c: Complex = Complex(2,1)
    val c_re: Double = 2
    val c_im: Double = 1
    value class transformation
    No object created!
    

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80. 80
    scala-miniboxing.org
    Value Classes
    Value Classes
    val a: Any = c
    

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81. 81
    scala-miniboxing.org
    Value Classes
    Value Classes
    val a: Any = c
    value class transformation
    

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82. 82
    scala-miniboxing.org
    Value Classes
    Value Classes
    val a: Any = c
    val a: Object =
    new Complex(c_re, c_im)
    value class transformation
    

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83. 83
    scala-miniboxing.org
    Value Classes
    Value Classes
    val a: Any = c
    val a: Object =
    new Complex(c_re, c_im)
    value class transformation
    Coercion!
    

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84. 84
    scala-miniboxing.org
    Value Classes
    Value Classes
    value class
    

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85. 85
    scala-miniboxing.org
    Value Classes
    Value Classes
    value class
    

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86. 86
    scala-miniboxing.org
    Value Classes
    Value Classes
    value class
    structure (by-val)
    ●
    preferred encoding
    

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87. 87
    scala-miniboxing.org
    Value Classes
    Value Classes
    value class
    structure (by-val)
    ●
    preferred encoding ●
    fallback encoding
    ●
    compatible with
    ●
    supertypes
    ●
    erased generics
    class (by-ref)
    

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88. 88
    scala-miniboxing.org
    Value Classes
    Value Classes
    value class
    structure (by-val)
    ●
    preferred encoding ●
    fallback encoding
    ●
    compatible with
    ●
    supertypes
    ●
    erased generics
    class (by-ref)
    incompatible
    → coercions
    

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89. scala-miniboxing.org
    What do auto(un)boxing,
    specialization and value
    classes have in common?
    

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90. scala-miniboxing.org
    What do auto(un)boxing,
    specialization and value
    classes have in common?
    Multi-stage programs too,
    but we won't go there!
    

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91. scala-miniboxing.org
    What do auto(un)boxing,
    specialization and value
    classes have in common?
    

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92. 92
    scala-miniboxing.org
    Auto(un)boxing
    Auto(un)boxing
    scala.Int
    int
    ●
    fast access
    ●
    no garbage collection
    ●
    locality
    ●
    indirect access
    ●
    garbage collection
    ●
    and object allocation
    ●
    no locality guarantees
    ●
    compatible with erased generics
    java.lang.Integer
    incompatible
    → coercions
    

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93. 93
    scala-miniboxing.org
    Miniboxing
    Miniboxing
    T
    long
    ●
    preferred encoding ●
    fallback encoding
    ●
    compatible with
    ●
    method calls
    ●
    supertypes
    ●
    erased generics
    T (erased to Object)
    incompatible
    → coercions
    

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94. 94
    scala-miniboxing.org
    Value Classes
    Value Classes
    value class
    structure (by-val)
    ●
    preferred encoding ●
    fallback encoding
    ●
    compatible with
    ●
    supertypes
    ●
    erased generics
    class (by-ref)
    incompatible
    → coercions
    

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95. scala-miniboxing.org
    What do auto(un)boxing,
    specialization and value
    classes have in common?
    

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96. scala-miniboxing.org
    What do auto(un)boxing,
    specialization and value
    classes have in common?
    Starting from a high-level concept:
    

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97. scala-miniboxing.org
    What do auto(un)boxing,
    specialization and value
    classes have in common?
    Starting from a high-level concept:
    (1) split it into multiple representations
    based on external constaints
    

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98. scala-miniboxing.org
    What do auto(un)boxing,
    specialization and value
    classes have in common?
    Starting from a high-level concept:
    (1) split it into multiple representations
    based on external constaints
    (2) introduce the necessary coercions when
    the representation has to be converted
    

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99. scala-miniboxing.org
    What do auto(un)boxing,
    specialization and value
    classes have in common?
    Why is this important?
    The transformation
    Benchmark
    Conclusion
    

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100. scala-miniboxing.org
     What do auto(un)boxing,
     specialization and value
     classes have in common?
     Why is this important?
     The transformation
     Benchmark
     Conclusion
     

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101. scala-miniboxing.org
     Why is this important?
     

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102. 102
     scala-miniboxing.org
     Late Data Layout (LDL)
     Late Data Layout (LDL)
     

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103. 103
     scala-miniboxing.org
     Late Data Layout (LDL)
     Late Data Layout (LDL)
     concept
     

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104. 104
     scala-miniboxing.org
     Late Data Layout (LDL)
     Late Data Layout (LDL)
     concept
     

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105. 105
     scala-miniboxing.org
     Late Data Layout (LDL)
     Late Data Layout (LDL)
     concept
     repr. 1
     

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106. 106
     scala-miniboxing.org
     Late Data Layout (LDL)
     Late Data Layout (LDL)
     concept
     repr. 1 repr. 2
     

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107. 107
     scala-miniboxing.org
     Late Data Layout (LDL)
     Late Data Layout (LDL)
     concept
     repr. 1 … repr. n
     repr. 2
     

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108. 108
     scala-miniboxing.org
     Late Data Layout (LDL)
     Late Data Layout (LDL)
     concept
     repr. 1 … repr. n
     repr. 2
     Constraints from the interaction
     with other language features:
     ●
     generics
     ●
     subtyping
     ●
     virtual dispatch
     ●
     DSL semantics (staging)
     

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109. 109
     scala-miniboxing.org
     Late Data Layout (LDL)
     Late Data Layout (LDL)
     concept
     repr. 1 … repr. n
     repr. 2
     Constraints from the interaction
     with other language features:
     ●
     generics
     ●
     subtyping
     ●
     virtual dispatch
     ●
     DSL semantics (staging)
     We've seen this pattern over
     and over again:
     ●
     autounboxing
     ●
     specialization
     ●
     value classes
     ●
     multi-stage programming
     ●
     function representation
     ●
     collection representation
     

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110. 110
     scala-miniboxing.org
     Collection Representation
     Collection Representation
     List[T]
     

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111. 111
     scala-miniboxing.org
     Collection Representation
     Collection Representation
     List[T]
     Stream[T]
     ●
     preferred encoding
     ●
     for pure comprehensions
     

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112. 112
     scala-miniboxing.org
     Collection Representation
     Collection Representation
     List[T]
     Stream[T]
     ●
     preferred encoding
     ●
     for pure comprehensions
     ●
     for impure comprehensions
     ●
     more expensive (needs to
     be materialized at each
     step)
     List[T]
     

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113. 113
     scala-miniboxing.org
     Collection Representation
     Collection Representation
     List[T]
     Stream[T]
     ●
     preferred encoding
     ●
     for pure comprehensions
     ●
     for impure comprehensions
     ●
     more expensive (needs to
     be materialized at each
     step)
     List[T]
     incompatible
     → coercions
     

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114. 114
     scala-miniboxing.org
     Collection Representation
     Collection Representation
     val c = List(1,2,3)
     val d = c.map(_+1).filter(_%2==0)
     val c = List(1,2,3)
     val d = c.map(_+1).filter(_%2==0)
     

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115. 115
     scala-miniboxing.org
     Collection Representation
     Collection Representation
     val c = List(1,2,3)
     val d = c.map(_+1).filter(_%2==0)
     Materialized list
     val c = List(1,2,3)
     val d = c.map(_+1).filter(_%2==0)
     

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116. 116
     scala-miniboxing.org
     Collection Representation
     Collection Representation
     val c = List(1,2,3)
     val d = c.map(_+1).filter(_%2==0)
     Materialized list Materialized list
     val c = List(1,2,3)
     val d = c.map(_+1).filter(_%2==0)
     

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117. 117
     scala-miniboxing.org
     Collection Representation
     Collection Representation
     val c = List(1,2,3)
     val d = c.map(_+1).filter(_%2==0)
     Materialized list Materialized list
     val c = List(1,2,3)
     val d = c.map(_+1).filter(_%2==0)
     

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118. 118
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     Collection Representation
     Collection Representation
     val c = List(1,2,3)
     val d = c.map(_+1).filter(_%2==0)
     Materialized list Materialized list
     val c: Stream[Int] =
     List(1,2,3).toStream
     val c = List(1,2,3)
     val d = c.map(_+1).filter(_%2==0)
     

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119. 119
     scala-miniboxing.org
     Collection Representation
     Collection Representation
     val c = List(1,2,3)
     val d = c.map(_+1).filter(_%2==0)
     Materialized list Materialized list
     val c: Stream[Int] =
     List(1,2,3).toStream
     val d: Stream[Int] =
     c.map(_+1).filter(_%2==0)
     val c = List(1,2,3)
     val d = c.map(_+1).filter(_%2==0)
     

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120. 120
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     Collection Representation
     Collection Representation
     val c = List(1,2,3)
     val d = c.map(_+1).filter(_%2==0)
     Materialized list Materialized list
     val c: Stream[Int] =
     List(1,2,3).toStream
     val d: Stream[Int] =
     c.map(_+1).filter(_%2==0)
     val c = List(1,2,3)
     val d = c.map(_+1).filter(_%2==0)
     No materialization!
     

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121. 121
     scala-miniboxing.org
     
     
     

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122. 122
     scala-miniboxing.org
     
     
     
     

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123. 123
     scala-miniboxing.org
     
     
     
     repr. 1 … repr. n
     repr. 2
     

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124. 124
     scala-miniboxing.org
     
     
     
     repr. 1 … repr. n
     repr. 2
     Can LDL help you?
     

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125. 125
     scala-miniboxing.org
     
     
     
     repr. 1 … repr. n
     repr. 2
     Can LDL help you? It may not be a perfect fit,
     but let's give it a shot!
     

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126. scala-miniboxing.org
     What do auto(un)boxing,
     specialization and value
     classes have in common?
     Why is this important?
     The transformation
     Benchmark
     Conclusion
     

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127. scala-miniboxing.org
     What do auto(un)boxing,
     specialization and value
     classes have in common?
     Why is this important?
     The transformation
     Benchmark
     Conclusion
     

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128. scala-miniboxing.org
     How do transform a program?
     

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129. scala-miniboxing.org
     How do transform a program?
     If you understand the
     high-level picture, you
     will immediately see if
     your usecase matches.
     

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130. scala-miniboxing.org
     How do transform a program?
     If you understand the
     high-level picture, you
     will immediately see if
     your usecase matches. We'll use autounboxing
     as the running example,
     to keep things simple
     

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131. 131
     scala-miniboxing.org
     Auto(un)boxing
     Auto(un)boxing
     scala.Int
     int
     ●
     fast access
     ●
     no garbage collection
     ●
     locality
     ●
     indirect access
     ●
     object allocation
     ●
     and thus garbage collection
     ●
     no locality guarantees
     ●
     compatible with erased generics
     java.lang.Integer
     

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132. 132
     scala-miniboxing.org
     Auto(un)boxing
     Auto(un)boxing
     scala.Int
     int
     ●
     fast access
     ●
     no garbage collection
     ●
     locality
     ●
     indirect access
     ●
     object allocation
     ●
     and thus garbage collection
     ●
     no locality guarantees
     ●
     compatible with erased generics
     java.lang.Integer
     incompatible
     → coercions
     

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133. scala-miniboxing.org
     Naive transformation
     Syntax-based transformation
     Type-based LDL transformation
     

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134. 134
     scala-miniboxing.org
     Naive transformation
     Naive transformation
     val x: Int = List[Int](1, 2, 3).head
     val y: List[Int] = List[Int](x)
     naive unboxing
     

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135. 135
     scala-miniboxing.org
     Naive transformation
     Naive transformation
     val x: Int = List[Int](1, 2, 3).head
     val y: List[Int] = List[Int](x)
     val x: int = List[Int](1, 2, 3).head
     val y: List[Int] = List[Int](x)
     naive unboxing
     

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136. 136
     scala-miniboxing.org
     Naive transformation
     Naive transformation
     val x: Int = List[Int](1, 2, 3).head
     val y: List[Int] = List[Int](x)
     val x: int = List[Int](1, 2, 3).head
     val y: List[Int] = List[Int](x)
     naive unboxing
     representation mismatch:
     expected: int
     found: Int
     

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137. 137
     scala-miniboxing.org
     Naive transformation
     Naive transformation
     val x: Int = List[Int](1, 2, 3).head
     val y: List[Int] = List[Int](x)
     val x: int = List[Int](1, 2, 3).head
     val y: List[Int] = List[Int](x)
     naive unboxing
     representation mismatch:
     expected: int
     found: Int
     representation mismatch:
     expected: Int
     found: int
     

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138. 138
     scala-miniboxing.org
     Naive transformation
     Naive transformation
     ●
     naively replacing representations
     – leads to mismatches
     – which are hard to recover
     (impossible for value classes and miniboxing)
     ●
     we need coercions between representations
     

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139. scala-miniboxing.org
     Naive transformation
     Syntax-based transformation
     Type-based LDL transformation
     

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140. 140
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     ●
     when transforming a value
     – coerce the definition right-hand side
     – coerce all references to it
     

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141. 141
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: Int = List[Int](1, 2, 3).head
     

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142. 142
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: Int = List[Int](1, 2, 3).head
     syntax-based unboxing
     

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143. 143
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: Int = List[Int](1, 2, 3).head
     val x: int =
     syntax-based unboxing
     

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144. 144
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: Int = List[Int](1, 2, 3).head
     val x: int =
     unbox(List[Int](1, 2, 3).head)
     syntax-based unboxing
     

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145. 145
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: Int = List[Int](1, 2, 3).head
     val x: int =
     unbox(List[Int](1, 2, 3).head)
     syntax-based unboxing
     There are no references to x,
     so there's nothing else to do.
     

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146. 146
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: Int = List[Int](1, 2, 3).head
     val x: int =
     unbox(List[Int](1, 2, 3).head)
     syntax-based unboxing
     There are no references to x,
     so there's nothing else to do.
     

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147. 147
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: Int = List[Int](1, 2, 3).head
     val y: Int = x
     

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148. 148
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: Int = List[Int](1, 2, 3).head
     val y: Int = x
     Transform one by one
     

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149. 149
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: Int = List[Int](1, 2, 3).head
     val y: Int = x
     syntax-based unboxing
     Transform one by one
     

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150. 150
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: Int = List[Int](1, 2, 3).head
     val y: Int = x
     val x: int =
     unbox(List[Int](1, 2, 3).head)
     syntax-based unboxing
     Transform one by one
     

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151. 151
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: Int = List[Int](1, 2, 3).head
     val y: Int = x
     val x: int =
     unbox(List[Int](1, 2, 3).head)
     val y: Int = box(x)
     syntax-based unboxing
     Transform one by one
     

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152. 152
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: int =
     unbox(List[Int](1, 2, 3).head)
     val y: Int = box(x)
     

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153. 153
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: int =
     unbox(List[Int](1, 2, 3).head)
     val y: Int = box(x)
     syntax-based unboxing
     

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154. 154
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: int =
     unbox(List[Int](1, 2, 3).head)
     val y: Int = box(x)
     val x: int =
     unbox(List[Int](1, 2, 3).head)
     val y: int =
     syntax-based unboxing
     

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155. 155
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: int =
     unbox(List[Int](1, 2, 3).head)
     val y: Int = box(x)
     val x: int =
     unbox(List[Int](1, 2, 3).head)
     val y: int = unbox(box(x))
     syntax-based unboxing
     

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156. 156
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     val x: int =
     unbox(List[Int](1, 2, 3).head)
     val y: Int = box(x)
     val x: int =
     unbox(List[Int](1, 2, 3).head)
     val y: int = unbox(box(x))
     syntax-based unboxing
     suboptimal
     

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157. 157
     scala-miniboxing.org
     Peephole Optimization
     Peephole Optimization
     val y: int = unbox(box(x))
     

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158. 158
     scala-miniboxing.org
     Peephole Optimization
     Peephole Optimization
     val y: int = unbox(box(x))
     peephole
     

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159. 159
     scala-miniboxing.org
     Peephole Optimization
     Peephole Optimization
     val y: int = unbox(box(x))
     val y: int = x
     peephole
     

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160. 160
     scala-miniboxing.org
     Peephole Optimization
     Peephole Optimization
     val y: int = unbox(box(x))
     val y: int = x
     peephole
     

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161. 161
     scala-miniboxing.org
     Peephole Optimization
     Peephole Optimization
     val y: int = unbox(box(x))
     val y: int = x
     peephole
     Okay, let's add the peephole
     transformation in the pipeline.
     

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162. 162
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     def choice(t1: Int, t2: Int): Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     

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163. 163
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     def choice(t1: Int, t2: Int): Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     Transform one by one
     

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164. 164
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     def choice(t1: int, t2: Int): Int =
     if (Random.nextBoolean())
     box(t1)
     else
     t2
     

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165. 165
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     def choice(t1: int, t2: int): Int =
     if (Random.nextBoolean())
     box(t1)
     else
     box(t2)
     

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166. 166
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     def choice(t1: int, t2: int): Int =
     if (Random.nextBoolean())
     box(t1)
     else
     box(t2)
     Anything missing?
     

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167. 167
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     def choice(t1: int, t2: int): int =
     unbox(if (Random.nextBoolean())
     box(t1)
     else
     box(t2))
     

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168. 168
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     def choice(t1: int, t2: int): int =
     unbox(if (Random.nextBoolean())
     box(t1)
     else
     box(t2))
     

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169. 169
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     def choice(t1: int, t2: int): int =
     unbox(if (Random.nextBoolean())
     box(t1)
     else
     box(t2))
     new peephole rule
     

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170. 170
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     def choice(t1: int, t2: int): int =
     unbox(if (Random.nextBoolean())
     box(t1)
     else
     box(t2))
     new peephole rule
     sink outside coercions
     into the if branches
     

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171. 171
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     def choice(t1: int, t2: int): int =
     if (Random.nextBoolean())
     unbox(box(t1))
     else
     unbox(box(t2))
     

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172. 172
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     def choice(t1: int, t2: int): int =
     if (Random.nextBoolean())
     unbox(box(t1))
     else
     unbox(box(t2))
     

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173. 173
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     def choice(t1: int, t2: int): int =
     if (Random.nextBoolean())
     t1
     else
     t2
     

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174. 174
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     def choice(t1: int, t2: int): int =
     if (Random.nextBoolean())
     t1
     else
     t2
     complicated
     

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175. 175
     scala-miniboxing.org
     Syntax-based
     Syntax-based
     ●
     peephole transformation does not scale
     – needs multiple rules for each node
     – needs successive rewriting => slow
     – impossible to guarantee optimality
     

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176. scala-miniboxing.org
     Naive transformation
     Syntax-based transformation
     Type-based LDL transformation
     

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177. 177
     scala-miniboxing.org
     Type-based transformation
     Type-based transformation
     ●
     propagate representation information
     – into the type system (based on annotated types)
     – let the type system propagate this information
     

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178. 178
     scala-miniboxing.org
     Type-based transformation
     Type-based transformation
     ●
     re-typechecking the tree
     – exposes inconsistencies in the representation
     – so we introduce coercions
     ●
     only when representations don't match
     

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179. 179
     scala-miniboxing.org
     Type-based transformation
     Type-based transformation
     ●
     three-stage mechanism
     – inject annotate the values to be unboxed
     →
     – coerce introduce coercion markers
     →
     – commit commit to the alternative representations
     →
     

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180. 180
     scala-miniboxing.org
     Type-based transformation
     Type-based transformation
     Warning!
     Throughout the presentation we'll be writing
     annotations written before types (e.g. “@unboxed
     Int”), although in the Scala syntax they are written
     after the type (e.g.“Int @unboxed”). This makes it
     easier to read the types aloud.
     

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181. 181
     scala-miniboxing.org
     Type-based
     Type-based inject
     coerce
     commit
     

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182. 182
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: Int,
     t2: Int): Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     

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183. 183
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: Int,
     t2: Int): Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     

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184. 184
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     

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185. 185
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     configurable introduction
     of annotations
     based on external constraints
     

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186. 186
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     

     View Slide

187. 187
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     

     View Slide

188. 188
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     

     View Slide

189. 189
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     the rhs expression must
     be of type @unboxed Int
     

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190. 190
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     : @unboxed Int
     the rhs expression must
     be of type @unboxed Int
     

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191. 191
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     : @unboxed Int
     expected type
     (part of local type inference)
     the rhs expression must
     be of type @unboxed Int
     

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192. 192
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     : Boolean
     

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193. 193
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     : Boolean
     matches:
     expected: Boolean
     found: Boolean
     

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194. 194
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     : @unboxed Int
     

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195. 195
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     : @unboxed Int
     matches:
     expected: @unboxed Int
     found: @unboxed Int
     

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196. 196
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     : @unboxed Int
     

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197. 197
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     matches:
     ...
     : @unboxed Int
     

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198. 198
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     

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199. 199
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     all okay, next phase
     

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200. 200
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     

     View Slide

201. 201
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: @unboxed Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     Replace:
     @unboxed Int → int
     (not showing Int → j.l.Integer)
     

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202. 202
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: int,
     t2: int): int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     

     View Slide

203. 203
     scala-miniboxing.org
     Type-based
     Type-based
     def choice(t1: int,
     t2: int): int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     that's it!
     

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204. 204
     scala-miniboxing.org
     Type-based transformation
     Type-based transformation
     ●
     three-stage mechanism
     – inject: add annotations
     – coerce: add coercions (based on the annotations)
     – commit: final representation semantics
     

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205. 205
     scala-miniboxing.org
     Type-based transformation
     Type-based transformation
     ●
     Scalac's erasure
     – similar transformation
     – less flexible (no annotations)
     – entangled with other transformations
     ●
     we took what's good
     – and allowed the transformation to work on other
     usecases as well
     

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206. 206
     scala-miniboxing.org
     Type-based transformation
     Type-based transformation
     ●
     why do this?
     – at the core of:
     ●
     miniboxing (http://scala-miniboxing.org)
     ●
     value classes plugin (https://github.com/miniboxing/value-plugin)
     ●
     multi-stage plugin (https://github.com/miniboxing/staging-plugin)
     ●
     
     

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207. 207
     scala-miniboxing.org
     Type-based transformation
     Type-based transformation
     ●
     why do this?
     – at the core of:
     ●
     miniboxing (http://scala-miniboxing.org)
     ●
     value classes plugin (https://github.com/miniboxing/value-plugin)
     ●
     multi-stage plugin (https://github.com/miniboxing/staging-plugin)
     ●
     
     most important one
     

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208. scala-miniboxing.org
     Consistency
     Selectivity
     Optimality*
     Properties
     Type-based LDL transformation
     * not formally proven yet
     

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209. 209
     scala-miniboxing.org
     Consistency
     Consistency inject
     coerce
     commit
     ●
     representations become explicit in types
     – representation mismatches
     ●
     become type mismatches
     ●
     are exposed by the type system
     – mismatches lead to coercions
     ●
     explicit bridges between representations
     ●
     are introduced automatically
     – regardless of the representations
     ●
     at a meta-level
     

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210. scala-miniboxing.org
     Consistency
     Selectivity
     Optimality*
     Properties
     Type-based LDL transformation
     * not formally proven yet
     

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211. 211
     scala-miniboxing.org
     Selectivity
     Selectivity inject
     coerce
     commit
     ●
     annotations allow selectively picking the values
     to be transformed
     – value classes
     ●
     cannot unbox multi-param values in return position (not
     supported by the JVM platform)
     ●
     bridge methods
     – staging
     ●
     annotations signal domain-specific knowledge
     – can occur inside generics (List[@staged Int])
     

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212. 212
     scala-miniboxing.org
     Selectivity
     Selectivity
     def choice(t1: Int,
     t2: Int): Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     

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213. 213
     scala-miniboxing.org
     Selectivity
     Selectivity
     def choice(t1: Int,
     t2: Int): Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     what if we did not annotate t1?
     

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214. 214
     scala-miniboxing.org
     Selectivity
     Selectivity
     def choice(t1: Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     what if we did not annotate t1?
     

     View Slide

215. 215
     scala-miniboxing.org
     Selectivity
     Selectivity
     def choice(t1: Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     : @unboxed Int
     

     View Slide

216. 216
     scala-miniboxing.org
     Selectivity
     Selectivity
     def choice(t1: Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     : @unboxed Int
     

     View Slide

217. 217
     scala-miniboxing.org
     Selectivity
     Selectivity
     def choice(t1: Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     : @unboxed Int
     mismatch:
     expected: @unboxed Int
     found: Int
     

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218. 218
     scala-miniboxing.org
     Selectivity
     Selectivity
     def choice(t1: Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     t1
     else
     t2
     inject
     coerce
     commit
     : @unboxed Int
     mismatch:
     expected: @unboxed Int
     found: Int
     coercion
     

     View Slide

219. 219
     scala-miniboxing.org
     Selectivity
     Selectivity
     def choice(t1: Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     unbox(t1)
     else
     t2
     inject
     coerce
     commit
     

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220. 220
     scala-miniboxing.org
     Selectivity
     Selectivity
     def choice(t1: Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     unbox(t1)
     else
     t2
     inject
     coerce
     commit
     

     View Slide

221. 221
     scala-miniboxing.org
     Selectivity
     Selectivity
     def choice(t1: Int,
     t2: int): int =
     if (Random.nextBoolean())
     t1.intValue
     else
     t2
     inject
     coerce
     commit
     

     View Slide

222. scala-miniboxing.org
     Consistency
     Selectivity
     Optimality*
     Properties
     Type-based LDL transformation
     * not formally proven yet
     

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223. 223
     scala-miniboxing.org
     Optimality
     Optimality
     def choice(t1: Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     unbox(t1)
     else
     t2
     inject
     coerce
     commit
     

     View Slide

224. 224
     scala-miniboxing.org
     Optimality
     Optimality
     def choice(t1: Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     unbox(t1)
     else
     t2
     inject
     coerce
     commit
     

     View Slide

225. 225
     scala-miniboxing.org
     Optimality
     Optimality
     def choice(t1: Int,
     t2: @unboxed Int): @unboxed Int =
     if (Random.nextBoolean())
     unbox(t1)
     else
     t2
     inject
     coerce
     commit
     Coercions are sunk in the tree →
     excute only if necessary
     

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226. scala-miniboxing.org
     Miniboxing
     Value Classes*
     Multi-stage Programming*
     Use cases
     Type-based LDL transformation
     * early prototypes
     

     View Slide

227. 227
     scala-miniboxing.org
     LDL for miniboxing
     LDL for miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = ...
     

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228. 228
     scala-miniboxing.org
     LDL for miniboxing
     LDL for miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = ...
     miniboxing
     

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229. 229
     scala-miniboxing.org
     LDL for miniboxing
     LDL for miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = ...
     miniboxing
     first: duplicate body
     

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230. 230
     scala-miniboxing.org
     LDL for miniboxing
     LDL for miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = ...
     miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = …
     first: duplicate body
     

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231. 231
     scala-miniboxing.org
     LDL for miniboxing
     LDL for miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = ...
     miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = …
     def tupled_ML[T1, T2](..., t1: T1, t2: T2) = …
     first: duplicate body
     

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232. 232
     scala-miniboxing.org
     LDL for miniboxing
     LDL for miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = ...
     miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = …
     def tupled_ML[T1, T2](..., t1: T1, t2: T2) = …
     def tupled_LM[T1, T2](..., t1: T1, t2: T2) = …
     first: duplicate body
     

     View Slide

233. 233
     scala-miniboxing.org
     LDL for miniboxing
     LDL for miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = ...
     miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = …
     def tupled_ML[T1, T2](..., t1: T1, t2: T2) = …
     def tupled_LM[T1, T2](..., t1: T1, t2: T2) = …
     def tupled_MM[T1, T2](..., t1: T1, t2: T2) = …
     first: duplicate body
     

     View Slide

234. 234
     scala-miniboxing.org
     LDL for miniboxing
     LDL for miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = ...
     miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = …
     def tupled_ML[T1, T2](..., t1: T1, t2: T2) = …
     def tupled_LM[T1, T2](..., t1: T1, t2: T2) = …
     def tupled_MM[T1, T2](..., t1: T1, t2: T2) = …
     first: duplicate body
     second: adapt it
     

     View Slide

235. 235
     scala-miniboxing.org
     LDL for miniboxing
     LDL for miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = ...
     miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = …
     def tupled_ML[T1, T2](..., t1: @long T1, t2: T2) = …
     def tupled_LM[T1, T2](..., t1: T1, t2: @long T2) = …
     def tupled_MM[T1, T2](..., t1: @long T1, t2: @long T2) =
     * @long is used instead of @storage[Long]
     second: adapt it
     first: duplicate body
     

     View Slide

236. 236
     scala-miniboxing.org
     LDL for miniboxing
     LDL for miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = ...
     miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = …
     def tupled_ML[T1, T2](..., t1: @long T1, t2: T2) = …
     def tupled_LM[T1, T2](..., t1: T1, t2: @long T2) = …
     def tupled_MM[T1, T2](..., t1: @long T1, t2: @long T2) =
     * @long is used instead of @storage[Long]
     second: adapt it
     using the transformation
     first: duplicate body
     

     View Slide

237. 237
     scala-miniboxing.org
     LDL for miniboxing
     LDL for miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = ...
     miniboxing
     def tupled[T1, T2](t1: T1, t2: T2) = …
     def tupled_ML[T1, T2](..., t1: @long T1, t2: T2) = …
     def tupled_LM[T1, T2](..., t1: T1, t2: @long T2) = …
     def tupled_MM[T1, T2](..., t1: @long T1, t2: @long T2) =
     * @long is used instead of @storage[Long]
     second: adapt it
     using the transformation
     first: duplicate body
     body gets adapted**
     

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238. scala-miniboxing.org
     Miniboxing
     Value Classes*
     Multi-stage Programming*
     Use cases
     Type-based LDL transformation
     * early prototypes
     

     View Slide

239. 239
     scala-miniboxing.org
     LDL for value classes
     LDL for value classes
     def abs(c: @unboxed Complex): Double = ...
     

     View Slide

240. 240
     scala-miniboxing.org
     LDL for value classes
     LDL for value classes
     def abs(c: @unboxed Complex): Double = ...
     value class plugin
     (commit phase)
     

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241. 241
     scala-miniboxing.org
     LDL for value classes
     LDL for value classes
     def abs(c: @unboxed Complex): Double = ...
     value class plugin
     (commit phase)
     def abs(c_re: Double, c_im: Double): Double = ...
     

     View Slide

242. 242
     scala-miniboxing.org
     LDL for value classes
     LDL for value classes
     def abs(c: @unboxed Complex): Double = ...
     value class plugin
     (commit phase)
     def abs(c_re: Double, c_im: Double): Double = ...
     

     View Slide

243. 243
     scala-miniboxing.org
     LDL for value classes
     LDL for value classes
     def abs(c: @unboxed Complex): Double = ...
     value class plugin
     (commit phase)
     def abs(c_re: Double, c_im: Double): Double = ...
     I'm hiding a lot of details here.
     But one could talk about this for an entire day
     

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244. 244
     scala-miniboxing.org
     LDL for value classes
     LDL for value classes
     def abs(c: @unboxed Complex): Double = ...
     value class plugin
     (commit phase)
     def abs(c_re: Double, c_im: Double): Double = ...
     I'm hiding a lot of details here.
     But one could talk about this for an entire day
     The one is @xeno-by!
     He implemented this :)
     

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245. scala-miniboxing.org
     Miniboxing
     Value Classes*
     Multi-stage Programming*
     Use cases
     Type-based LDL transformation
     * early prototypes
     

     View Slide

246. scala-miniboxing.org
     Miniboxing
     Value Classes*
     Multi-stage Programming*
     Use cases
     Type-based LDL transformation
     We won't go into it today, but see
     github.com/miniboxing/staging-plugin
     * early prototypes
     

     View Slide

247. scala-miniboxing.org
     What do auto(un)boxing,
     specialization and value
     classes have in common?
     Why is this important?
     The transformation
     Benchmark
     Conclusion
     

     View Slide

248. scala-miniboxing.org
     What do auto(un)boxing,
     specialization and value
     classes have in common?
     Why is this important?
     The transformation
     Benchmark
     Conclusion
     

     View Slide

249. 249
     scala-miniboxing.org
     Miniboxing Benchmarks
     Miniboxing Benchmarks
     on the Scala library
     on the Scala library
     ●
     benchmark: Least Squares Method
     – using a mockup of scala.collection.immutable.List
     

     View Slide

250. 250
     scala-miniboxing.org
     Miniboxing Benchmarks
     Miniboxing Benchmarks
     on the Scala library
     on the Scala library
     ●
     work with Aymeric Genet (github: @MelodyLucid)
     ●
     mock-up of Scala linked List
     – Tuples
     – Traversable/TraversableLike
     – Iterator/Iterable/IterableLike
     – LinearSeqOptimized
     – Builder/CanBuildFrom
     ●
     FunctionX has a nice story
     

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251. 251
     scala-miniboxing.org
     Miniboxing Benchmarks
     Miniboxing Benchmarks
     on the Scala library
     on the Scala library
     ●
     FunctionX from the Scala library
     – specialized
     – no way to call from miniboxed code without boxing slow
     →
     ●
     MiniboxedFunctionX benchmarked
     ←
     – miniboxed, call without coercing
     – added automatically with another LDL cycle
     ●
     MyFunctionX benchmarked
     ←
     – miniboxed, call without coercing
     – added by hand to the library
     

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252. 252
     scala-miniboxing.org
     Miniboxing Benchmarks
     Miniboxing Benchmarks
     on the Scala library
     on the Scala library
     

     View Slide

253. 253
     scala-miniboxing.org
     Miniboxing Benchmarks
     Miniboxing Benchmarks
     on the Scala library
     on the Scala library
     30%-45% faster
     

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254. 254
     scala-miniboxing.org
     Miniboxing Benchmarks
     Miniboxing Benchmarks
     on the Scala library
     on the Scala library
     30%-45% faster
     On a non-contiguous
     data structure
     

     View Slide

255. 255
     scala-miniboxing.org
     Miniboxing Benchmarks
     Miniboxing Benchmarks
     on the Scala library (with GC)
     on the Scala library (with GC)
     

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256. 256
     scala-miniboxing.org
     Miniboxing Benchmarks
     Miniboxing Benchmarks
     on the Scala library (with GC)
     on the Scala library (with GC)
     3x faster
     On a non-contiguous
     data structure
     

     View Slide

257. scala-miniboxing.org
     What do auto(un)boxing,
     specialization and value
     classes have in common?
     Why is this important?
     The transformation
     Benchmark
     Conclusion
     

     View Slide

258. scala-miniboxing.org
     What do auto(un)boxing,
     specialization and value
     classes have in common?
     Why is this important?
     The transformation
     Benchmark
     Conclusion
     `
     

     View Slide

259. 259
     scala-miniboxing.org
     Conclusion
     Conclusion
     LDL is a
     LDL is a transformation
     transformation
     ●
     that allows splitting a high-level concept
     – into multiple representations
     – in a consistent way (through coercions)
     – in a selective way (through annotations)
     – in an optimal way (coerce only if necessary)
     ●
     use cases covered
     – miniboxing
     – value classes
     ●
     what is your use case?
     
     repr. 1 … repr. n
     repr. 2
     

     View Slide

260. scala-miniboxing.org
     Credits and Thank you-s
     ●
     Cristian Talau - developed the initial prototype, as a semester project
     ●
     Eugene Burmako - the value class plugin based on the LDL transformation
     ●
     Aymeric Genet - developing collection-like benchmarks for the miniboxing plugin
     ●
     Martin Odersky, for his patient guidance
     ●
     Eugene Burmako, for trusting the idea enough to develop the value-plugin based on the LDL transformation
     ●
     Iulian Dragos, for his work on specialization and many explanations
     ●
     Miguel Garcia, for his original insights that spawned the miniboxing idea
     ●
     Michel Schinz, for his wonderful comments and enlightening ACC course
     ●
     Andrew Myers and Roland Ducournau for the discussions we had and the feedback provided
     ●
     Heather Miller for the eye-opening discussions we had
     ●
     Vojin Jovanovic, Sandro Stucki, Manohar Jonalagedda and the whole LAMP laboratory in EPFL for the extraordinary atmosphere
     ●
     Adriaan Moors, for the miniboxing name which stuck :))
     ●
     Thierry Coppey, Vera Salvisberg and George Nithin, who patiently listened to many presentations and provided valuable feedback
     ●
     Grzegorz Kossakowski, for the many brainstorming sessions on specialization
     ●
     Erik Osheim, Tom Switzer and Rex Kerr for their guidance on the Scala community side
     ●
     OOPSLA paper and artifact reviewers, who reshaped the paper with their feedback
     ●
     Sandro, Vojin, Nada, Heather, Manohar - reviews and discussions on the LDL paper
     ●
     Hubert Plociniczak for the type notation in the LDL paper
     ●
     Denys Shabalin, Dmitry Petrashko for their patient reviews of the LDL paper
     Special thanks to the Scala Community for their support!
     (@StuHood, @vpatryshev and everyone else!)
     

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261. 261
     scala-miniboxing.org
     Conclusion
     Conclusion
     LDL is a
     LDL is a transformation
     transformation
     ●
     that allows splitting a high-level concept
     – into multiple representations
     – in a consistent way (through coercions)
     – in a selective way (through annotations)
     – in an optimal way (coerce only if necessary)
     ●
     use cases covered
     – miniboxing
     – value classes
     ●
     what is your use case?
     
     repr. 1 … repr. n
     repr. 2
     

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262. scala-miniboxing.org
     ScalaTeam @ EPFL
     

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263. scala-miniboxing.org
     ScalaTeam @ EPFL
     ●
     Dependent Object Types calculus
     – core type system of the dotty compiler
     – Nada Amin/Tiark Rompf
     https://github.com/TiarkRompf/minidot
     https://github.com/lampepfl/dotty
     

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264. scala-miniboxing.org
     ScalaTeam @ EPFL
     ●
     YinYang multi-stage macro-based frontend
     – replacement for scala-virtualized
     – Vojin Jovanovic/Sandro Stucki + others
     https://github.com/vjovanov/yin-yang
     

     View Slide

265. scala-miniboxing.org
     ScalaTeam @ EPFL
     ●
     Scala.js backend
     – compiles Scala to JavaScript
     – Sébastien Doeraene/Tobias Schlatter + others
     http://www.scala-js.org/
     www
     

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266. scala-miniboxing.org
     ScalaTeam @ EPFL
     ●
     Staged Parser-combinators
     – fast parser combinators through staging
     – Manohar Jonnalagedda + others
     https://github.com/manojo/experiments
     

     View Slide

267. scala-miniboxing.org
     ScalaTeam @ EPFL
     ●
     Pickling framework and Spores
     – support for distributed programming
     – Heather Miller/Philipp Haller + others
     https://github.com/scala/pickling
     https://github.com/heathermiller/spores
     

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268. scala-miniboxing.org
     ScalaTeam @ EPFL
     ●
     dotty
     – experimental compiler based on DOT
     – Martin Odersky/Dmitry Petrashko/Samuel
     Grütter/Tobias Schlatter + others
     https://github.com/lampepfl/dotty
     

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269. scala-miniboxing.org
     ScalaTeam @ EPFL
     ●
     scala.meta metaprogramming support
     – Improved reflection, macros, and many more
     – Eugene Burmako/Denys Shabalin + others
     http://scalameta.org/
     www
     

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270. scala-miniboxing.org
     ScalaTeam @ EPFL
     ●
     miniboxing specialization
     – LDL transformation
     – Vlad Ureche/Aymeric Genêt + others
     http://scala-miniboxing.org/
     www
     

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271. scala-miniboxing.org
     ScalaTeam @ EPFL
     ●
     scaladyno plugin
     – giving Scala a dynamic language look and feel
     – Cédric Bastin/Vlad Ureche
     https://github.com/scaladyno/scaladyno-plugin
     

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272. scala-miniboxing.org
     ScalaTeam @ EPFL
     ●
     ScalaBlitz optimization framework
     – macro-based collection optimization
     – Dmitry Petrashko/Aleksandar Prokopec
     http://scala-blitz.github.io/
     www
     

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273. scala-miniboxing.org
     ScalaTeam @ EPFL
     ●
     Type debugger for Scala
     – debugging aid for Scala type errors
     – Hubert Plociniczak
     http://lampwww.epfl.ch/~plocinic/
     type-debugger-tutorial/
     www
     

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274. scala-miniboxing.org
     ScalaTeam @ EPFL
     ●
     ScalaMeter benchmarking framework
     – google caliper for scala
     – Aleksandar Prokopec
     http://scalameter.github.io/
     www
     

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275. scala-miniboxing.org
     ScalaTeam @ EPFL
     ●
     the new scalac backend
     – good performance gains
     – Miguel Garcia
     ●
     on the job market right now
     http://magarciaepfl.github.io/scala/
     www
     @ miguel.garcia@tuhh.de
     

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276. scala-miniboxing.org 1st of August 2014
     Scala Bay Area Meetup
     Linkedin HQ, Mountain View
     Thank you!
     

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