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Merged
merged 3 commits into from
May 17, 2023
Merged

Special-case array/list/ReadOnlyDictionary in Dictionary(IEnumerable, …) ctors #86254

merged 3 commits into from
May 17, 2023

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stephentoub
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It's reasonably common to construct a dictionary from a KeyValuePair<TKey, TValue>[] or a List<KeyValuePair<TKey, TValue>>, and we can make both cheaper. We can also unwrap a Dictionary wrapped in a ReadOnlyDictionary in order to better utliize the existing optimizations around Dictionary.

Method Toolchain Length Mean Ratio Allocated Alloc Ratio
FromArray \main\corerun.exe 1 60.18 ns 1.00 224 B 1.00
FromArray \pr\corerun.exe 1 45.21 ns 0.75 192 B 0.86
FromList \main\corerun.exe 1 66.58 ns 1.00 232 B 1.00
FromList \pr\corerun.exe 1 46.90 ns 0.70 192 B 0.83
FromOther \main\corerun.exe 1 67.22 ns 1.00 240 B 1.00
FromOther \pr\corerun.exe 1 72.64 ns 1.07 240 B 1.00
FromReadOnlyDictionary \main\corerun.exe 1 70.60 ns 1.00 240 B 1.00
FromReadOnlyDictionary \pr\corerun.exe 1 45.04 ns 0.64 192 B 0.80
FromArray \main\corerun.exe 10 161.57 ns 1.00 384 B 1.00
FromArray \pr\corerun.exe 10 123.19 ns 0.75 352 B 0.92
FromList \main\corerun.exe 10 194.36 ns 1.00 392 B 1.00
FromList \pr\corerun.exe 10 118.41 ns 0.61 352 B 0.90
FromOther \main\corerun.exe 10 282.64 ns 1.00 824 B 1.00
FromOther \pr\corerun.exe 10 281.12 ns 0.98 824 B 1.00
FromReadOnlyDictionary \main\corerun.exe 10 218.75 ns 1.00 400 B 1.00
FromReadOnlyDictionary \pr\corerun.exe 10 78.69 ns 0.36 352 B 0.88
FromArray \main\corerun.exe 100 1,068.79 ns 1.00 2304 B 1.00
FromArray \pr\corerun.exe 100 764.88 ns 0.71 2272 B 0.99
FromList \main\corerun.exe 100 1,365.59 ns 1.00 2312 B 1.00
FromList \pr\corerun.exe 100 834.13 ns 0.61 2272 B 0.98
FromOther \main\corerun.exe 100 2,122.52 ns 1.00 7440 B 1.00
FromOther \pr\corerun.exe 100 2,136.31 ns 1.01 7440 B 1.00
FromReadOnlyDictionary \main\corerun.exe 100 1,660.43 ns 1.00 2320 B 1.00
FromReadOnlyDictionary \pr\corerun.exe 100 421.00 ns 0.25 2272 B 0.98
FromArray \main\corerun.exe 1000 10,293.70 ns 1.00 22224 B 1.00
FromArray \pr\corerun.exe 1000 7,303.10 ns 0.71 22192 B 1.00
FromList \main\corerun.exe 1000 12,777.52 ns 1.00 22232 B 1.00
FromList \pr\corerun.exe 1000 7,868.13 ns 0.62 22192 B 1.00
FromOther \main\corerun.exe 1000 20,186.57 ns 1.00 73216 B 1.00
FromOther \pr\corerun.exe 1000 20,459.95 ns 1.01 73216 B 1.00
FromReadOnlyDictionary \main\corerun.exe 1000 16,134.17 ns 1.00 22240 B 1.00
FromReadOnlyDictionary \pr\corerun.exe 1000 4,001.67 ns 0.25 22192 B 1.00 
private KeyValuePair<int, int>[] _array;
private List<KeyValuePair<int, int>> _list;
private IEnumerable<KeyValuePair<int, int>> _other;
private ReadOnlyDictionary<int, int> _rod;

[Params(1, 10, 100, 1000)]
public int Length { get; set; }

[GlobalSetup]
public void Setup()
{
    _array = Enumerable.Range(0, Length).Select(i => new KeyValuePair<int, int>(i, i)).ToArray();
    _list = new List<KeyValuePair<int, int>>(_array);
    _other = _array.Select(kvp => kvp);
    _rod = new ReadOnlyDictionary<int, int>(_array.ToDictionary(kvp => kvp.Key, kvp => kvp.Value));
}

[Benchmark] public Dictionary<int, int> FromArray() => new Dictionary<int, int>(_array);
[Benchmark] public Dictionary<int, int> FromList() => new Dictionary<int, int>(_list);
[Benchmark] public Dictionary<int, int> FromOther() => new Dictionary<int, int>(_other);
[Benchmark] public Dictionary<int, int> FromReadOnlyDictionary() => new Dictionary<int, int>(_rod);

@stephentoub stephentoub added this to the 8.0.0 milestone May 15, 2023
@ghost ghost assigned stephentoub May 15, 2023
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ghost commented May 15, 2023

Tagging subscribers to this area: @dotnet/area-system-collections
See info in area-owners.md if you want to be subscribed.

Issue Details

It's reasonably common to construct a dictionary from a KeyValuePair<TKey, TValue>[] or a List<KeyValuePair<TKey, TValue>>, and we can make both cheaper. We can also unwrap a Dictionary wrapped in a ReadOnlyDictionary in order to better utliize the existing optimizations around Dictionary.

Method Toolchain Length Mean Ratio Allocated Alloc Ratio
FromArray \main\corerun.exe 1 60.18 ns 1.00 224 B 1.00
FromArray \pr\corerun.exe 1 45.21 ns 0.75 192 B 0.86
FromList \main\corerun.exe 1 66.58 ns 1.00 232 B 1.00
FromList \pr\corerun.exe 1 46.90 ns 0.70 192 B 0.83
FromOther \main\corerun.exe 1 67.22 ns 1.00 240 B 1.00
FromOther \pr\corerun.exe 1 72.64 ns 1.07 240 B 1.00
FromReadOnlyDictionary \main\corerun.exe 1 70.60 ns 1.00 240 B 1.00
FromReadOnlyDictionary \pr\corerun.exe 1 45.04 ns 0.64 192 B 0.80
FromArray \main\corerun.exe 10 161.57 ns 1.00 384 B 1.00
FromArray \pr\corerun.exe 10 123.19 ns 0.75 352 B 0.92
FromList \main\corerun.exe 10 194.36 ns 1.00 392 B 1.00
FromList \pr\corerun.exe 10 118.41 ns 0.61 352 B 0.90
FromOther \main\corerun.exe 10 282.64 ns 1.00 824 B 1.00
FromOther \pr\corerun.exe 10 281.12 ns 0.98 824 B 1.00
FromReadOnlyDictionary \main\corerun.exe 10 218.75 ns 1.00 400 B 1.00
FromReadOnlyDictionary \pr\corerun.exe 10 78.69 ns 0.36 352 B 0.88
FromArray \main\corerun.exe 100 1,068.79 ns 1.00 2304 B 1.00
FromArray \pr\corerun.exe 100 764.88 ns 0.71 2272 B 0.99
FromList \main\corerun.exe 100 1,365.59 ns 1.00 2312 B 1.00
FromList \pr\corerun.exe 100 834.13 ns 0.61 2272 B 0.98
FromOther \main\corerun.exe 100 2,122.52 ns 1.00 7440 B 1.00
FromOther \pr\corerun.exe 100 2,136.31 ns 1.01 7440 B 1.00
FromReadOnlyDictionary \main\corerun.exe 100 1,660.43 ns 1.00 2320 B 1.00
FromReadOnlyDictionary \pr\corerun.exe 100 421.00 ns 0.25 2272 B 0.98
FromArray \main\corerun.exe 1000 10,293.70 ns 1.00 22224 B 1.00
FromArray \pr\corerun.exe 1000 7,303.10 ns 0.71 22192 B 1.00
FromList \main\corerun.exe 1000 12,777.52 ns 1.00 22232 B 1.00
FromList \pr\corerun.exe 1000 7,868.13 ns 0.62 22192 B 1.00
FromOther \main\corerun.exe 1000 20,186.57 ns 1.00 73216 B 1.00
FromOther \pr\corerun.exe 1000 20,459.95 ns 1.01 73216 B 1.00
FromReadOnlyDictionary \main\corerun.exe 1000 16,134.17 ns 1.00 22240 B 1.00
FromReadOnlyDictionary \pr\corerun.exe 1000 4,001.67 ns 0.25 22192 B 1.00 
private KeyValuePair<int, int>[] _array;
private List<KeyValuePair<int, int>> _list;
private IEnumerable<KeyValuePair<int, int>> _other;
private ReadOnlyDictionary<int, int> _rod;

[Params(1, 10, 100, 1000)]
public int Length { get; set; }

[GlobalSetup]
public void Setup()
{
    _array = Enumerable.Range(0, Length).Select(i => new KeyValuePair<int, int>(i, i)).ToArray();
    _list = new List<KeyValuePair<int, int>>(_array);
    _other = _array.Select(kvp => kvp);
    _rod = new ReadOnlyDictionary<int, int>(_array.ToDictionary(kvp => kvp.Key, kvp => kvp.Value));
}

[Benchmark] public Dictionary<int, int> FromArray() => new Dictionary<int, int>(_array);
[Benchmark] public Dictionary<int, int> FromList() => new Dictionary<int, int>(_list);
[Benchmark] public Dictionary<int, int> FromOther() => new Dictionary<int, int>(_other);
[Benchmark] public Dictionary<int, int> FromReadOnlyDictionary() => new Dictionary<int, int>(_rod);
Author: stephentoub
Assignees: -
Labels:

area-System.Collections, tenet-performance
Milestone: 8.0.0

@stephentoub stephentoub mentioned this pull request May 15, 2023
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@runfoapp runfoapp bot mentioned this pull request May 15, 2023
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@build-analysis build-analysis bot mentioned this pull request May 15, 2023
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@stephentoub
Special-case array/list/ReadOnlyDictionary in Dictionary(IEnumerable,…
6235656 
… ...) ctors

It's reasonably common to construct a dictionary from a `KeyValuePair<TKey, TValue>[]` or a `List<KeyValuePair<TKey, TValue>>`, and we can make both cheaper.  We can also unwrap a Dictionary wrapped in a ReadOnlyDictionary in order to better utliize the existing optimizations around Dictionary.
@stephentoub
Address PR feedback
8ed9267
@build-analysis build-analysis bot mentioned this pull request May 17, 2023
Open
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@stephentoub stephentoub merged commit 709444f into dotnet:main May 17, 2023
@stephentoub stephentoub deleted the dictionaryctor branch May 17, 2023 14:23
@ghost ghost locked as resolved and limited conversation to collaborators Jun 16, 2023
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@eiriktsarpalis eiriktsarpalis eiriktsarpalis approved these changes

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