Introduction to Swift Performance - Try! Swift 2016

Transcript

1. An Introduction to
   Swift Performance
   Danielle Tomlinson - @dantoml
   

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2. What makes code slow?
   

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3. Allocation
   

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4. Stack
   

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5. Heap
   

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6. Reference Counting
   

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7. func perform(with object: Object) {
   object.doAThing()
   }
   

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8. func perform(with object: Object) {
   __swift_retain(object)
   object.doAThing()
   __swift_release(object)
   }
   

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9. Dispatch
   

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10. Inline (0ns)
    

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11. Static (~1ns)
    

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12. Dynamic (~5ns)
    

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13. Objects
    

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14. Classes
    

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15. p: Index*
    Stack
    class Index {
    let section: Int
    let item: Int
    }
    let i = Index(section: 1,
    item: 1)
    Heap
    section: Int
    item: Int
    

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16. i: Index*
    Stack
    class Index {
    let section: Int
    let item: Int
    }
    let i = Index(section: 1,
    item: 1)
    let i2 = i
    Heap
    section: Int
    item: Int
    i2: Index*
    

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17. i: Index*
    Stack
    class Index {
    let section: Int
    let item: Int
    }
    let i = Index(section: 1,
    item: 1)
    __swift_retain(i)
    let i2 = i
    Heap
    section: Int
    item: Int
    i2: Index*
    

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18. Structs
    

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19. Stack
    

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20. section: 1
    item: 1
    Stack
    struct Index {
    let section: Int
    let item: Int
    }
    let i = Index(section: 1, item: 1)
    

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21. Stack
    struct Index {
    let section: Int
    let item: Int
    }
    let i = Index(section: 1, item: 1)
    let i2 = i
    section: 1
    item: 1
    section: 1
    item: 1
    

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22. name: StringA*
    id: StringB*
    Stack
    struct User {
    let name: String
    let id: String
    }
    let u = User(name: "Joe", id: "1234")
    

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23. name: StringA*
    id: StringB*
    Stack
    name: StringA*
    id: StringB*
    struct User {
    let name: String
    let id: String
    }
    let u = User(name: "Joe",
    id: "1234")
    __swift_retain(u.name._textStorage)
    __swift_retain(u.id._textStorage)
    let u2 = u
    

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24. Abstractions
    

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25. Example (0.3s)
    :
    struct Circle {
    let radius: Double
    let center: Point
    func draw() {}
    }
    var circles = (1..<100_000_000).map { _ in Circle(...) }
    for circle in circles {
    circle.draw()
    }
    

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26. Requirements Change
    

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27. Protocols
    

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28. Example (4s)
    :
    protocol Drawable {
    func draw()
    }
    struct Circle: Drawable {
    let radius: Double
    let center: Point
    func draw() {}
    }
    let drawables: [Drawable] = (1..<100_000_000).map { _ in Circle(...) }
    for drawable in drawables {
    drawable.draw()
    }
    

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29. Why?
    

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30. struct Circle {
    let radius: Double
    let center: Point
    func draw() {}
    }
    var circles = (1..<100_000_000).map { _ in Circle(...) }
    for circle in circles {
    circle.draw()
    }
    

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31. protocol Drawable {
    func draw()
    }
    struct Circle: Drawable {
    let radius: Double
    let center: Point
    func draw() {}
    }
    var drawables: [Drawable] = (1..<100_000_000).map { _ in return Circle(...) }
    for drawable in drawables {
    drawable.draw()
    }
    

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32. ProtocolWitnessTable
    draw()
    CircleDrawable
    ...
    draw()
    LineDrawable
    ...
    

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33. protocol Drawable {
    func draw()
    }
    struct Circle: Drawable {
    let radius: Double
    let center: Point
    func draw() {}
    }
    var drawables: [Drawable] = (1..<100_000_000).map { _ in
    return Circle(...)
    }
    for drawable in drawables {
    drawable.draw()
    }
    draw()
    CircleDrawable
    ...
    

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34. ExistentialContainer
    ValueBuffer
    ProtocolWitnessTable
    

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35. ExistentialContainer
    radius
    struct Circle: Drawable {
    let radius: Double
    let center: Point
    func draw() {}
    }
    center
    

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36. ExistentialContainer
    struct Line: Drawable {
    let origin: Point
    let end: Point
    func draw() {}
    }
    Origin
    End
    

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37. Example (45s)
    :
    protocol Drawable {
    func draw()
    }
    struct Line: Drawable {
    let origin: Point
    let end: Point
    func draw() {}
    }
    let drawables: [Drawable] = (1..<100_000_000).map { _ in Line(...) }
    for drawable in drawables {
    drawable.draw()
    }
    

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39. ValueWitnessTable
    ValueBuffer
    allocate:
    copy:
    destruct:
    deallocate:
    

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40. In Practice
    Stack
    origin
    Line
    vwt
    pwt
    end
    LineDrawable
    copy:
    ...
    Heap
    drawable:
    func draw(drawable: Drawable) {
    drawable.draw()
    }
    let value: Drawable = Line()
    draw(local: value)
    // Generates
    func draw(value: ECTDrawable) {
    var drawable: ECTDrawable = ECTDrawable()
    let vwt = value.vwt
    let pwt = value.pwt
    drawable.vwt = value.vwt
    drawable.pwt = value.pwt
    vwt.allocateBuffAndCopyValue(&drawable, value)
    pwt.draw(vwt.projectBuffer(&drawable)
    }
    

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41. Modelling Your Data
    

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42. Generics
    

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43. struct Stack {
    ...
    }
    

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44. Enumerations
    

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45. enum AccountStatus: String, RawRepresentable {
    case .banned, .verified, incomplete
    }
    

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46. Domain Specific Models
    

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47. Thanks!
    Office Hours: 16:30 in the Atrium. @dantoml
    

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