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Optimizing
Swift Collections
Károly Lőrentey
@lorentey
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NSOrderedSet
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40x
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40x
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left right
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Empty Tree Black node Red node
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.empty .node(color, a, x, b)
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2.5x
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2.5x
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2.5x
???
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3 allocations
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10 atomic refCount ops
t.insert(10)
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COW
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opy
C
Write
on
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COWTree
root:
COWNode
color:
value: 10
left:
right:
COWNode COWNode
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!
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4.5x
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4.5x
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O(n)
Linear Time
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O(1)
Constant Time
O(n)
Linear Time
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O(1)
Constant Time
O(n)
Linear Time
4096
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4096
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Ints
4096
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4096 × 8 bytes
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4096 × 8 bytes
= 32 kB
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4096 × 8 bytes
= 32 kB
= size of L1 cache
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B-tree
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3.5x
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Reuse an existing Collection
♻
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Reuse an existing Collection
♻
Functional programming
with algebraic data types
λ
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Reuse an existing Collection
♻
Imperative rewrite with
COW optimization
#
Functional programming
with algebraic data types
λ
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Reuse an existing Collection
♻
Cache-aware data structures
and unsafe operations
⚙
Imperative rewrite with
COW optimization
#
Functional programming
with algebraic data types
λ
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Reuse an existing Collection
♻
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import BTree
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import BTree
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22m 40s
SortedArray NSOrderedSet AlgebraicTree COWTree BTree/1024
Time spent inserting 3 million random values
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22m 40s
SortedArray NSOrderedSet AlgebraicTree COWTree BTree/1024
1.8s
7s
22s
14m 54s
22m 36s
Time spent inserting 3 million random values
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Thank You!
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Thank You!
lorentey
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Thank You!
lorentey @lorentey
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Acknowledgements
Cow picture courtesy of
freegreatpicture.com
Puppy pictures courtesy of
Floppy the Beagle