Tweak Enumerable.ToArray to reduce some overheads

[stephentoub]

Fixes dotnet/perf-autofiling-issues#27364
Fixes #96852

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

BenchmarkSwitcher.FromAssembly(typeof(Tests).Assembly).Run(args);

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

    [GlobalSetup]
    public void Setup()
    {
        _intsCollection = Enumerable.Range(0, Length).ToArray();
        _objectsCollection = Enumerable.Repeat(new object(), Length).ToArray();
        _intsEnumerable = Iterate(Enumerable.Range(0, Length).ToArray());
        _objectEnumerable = Iterate(Enumerable.Repeat(new object(), Length).ToArray());
    }

    private IEnumerable<int> _intsCollection;
    private IEnumerable<object> _objectsCollection;
    private IEnumerable<int> _intsEnumerable;
    private IEnumerable<object> _objectEnumerable;

    [Benchmark]
    public int[] IntCollection() => _intsCollection.ToArray();

    [Benchmark]
    public object[] ObjectCollection() => _objectsCollection.ToArray();

    [Benchmark]
    public int[] IntEnumerable() => _intsEnumerable.ToArray();

    [Benchmark]
    public object[] ObjectEnumerable() => _objectEnumerable.ToArray();

    private static IEnumerable<T> Iterate<T>(IEnumerable<T> source)
    {
        foreach (var item in source) yield return item;
    }
}

Method	Toolchain	Length	Mean	Ratio
IntCollection	\main\corerun.exe	1	18.68 ns	1.00
IntCollection	\pr\corerun.exe	1	15.73 ns	0.84
ObjectCollection	\main\corerun.exe	1	35.72 ns	1.00
ObjectCollection	\pr\corerun.exe	1	31.48 ns	0.88
IntEnumerable	\main\corerun.exe	1	49.37 ns	1.00
IntEnumerable	\pr\corerun.exe	1	48.62 ns	0.98
ObjectEnumerable	\main\corerun.exe	1	86.93 ns	1.00
ObjectEnumerable	\pr\corerun.exe	1	82.68 ns	0.95
IntCollection	\main\corerun.exe	10	21.33 ns	1.00
IntCollection	\pr\corerun.exe	10	18.99 ns	0.92
ObjectCollection	\main\corerun.exe	10	45.16 ns	1.00
ObjectCollection	\pr\corerun.exe	10	42.48 ns	0.94
IntEnumerable	\main\corerun.exe	10	130.02 ns	1.00
IntEnumerable	\pr\corerun.exe	10	126.27 ns	0.96
ObjectEnumerable	\main\corerun.exe	10	261.53 ns	1.00
ObjectEnumerable	\pr\corerun.exe	10	248.10 ns	0.95
IntCollection	\main\corerun.exe	1000	388.00 ns	1.00
IntCollection	\pr\corerun.exe	1000	393.29 ns	1.01
ObjectCollection	\main\corerun.exe	1000	839.89 ns	1.00
ObjectCollection	\pr\corerun.exe	1000	844.79 ns	1.01
IntEnumerable	\main\corerun.exe	1000	5,990.03 ns	1.00
IntEnumerable	\pr\corerun.exe	1000	5,456.53 ns	0.91
ObjectEnumerable	\main\corerun.exe	1000	11,796.91 ns	1.00
ObjectEnumerable	\pr\corerun.exe	1000	11,928.09 ns	1.01

[ghost]

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

Issue Details

---

Fixes dotnet/perf-autofiling-issues#27364
Fixes #96852

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

BenchmarkSwitcher.FromAssembly(typeof(Tests).Assembly).Run(args);

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

    [GlobalSetup]
    public void Setup()
    {
        _intsCollection = Enumerable.Range(0, Length).ToArray();
        _objectsCollection = Enumerable.Repeat(new object(), Length).ToArray();
        _intsEnumerable = Iterate(Enumerable.Range(0, Length).ToArray());
        _objectEnumerable = Iterate(Enumerable.Repeat(new object(), Length).ToArray());
    }

    private IEnumerable<int> _intsCollection;
    private IEnumerable<object> _objectsCollection;
    private IEnumerable<int> _intsEnumerable;
    private IEnumerable<object> _objectEnumerable;

    [Benchmark]
    public int[] IntCollection() => _intsCollection.ToArray();

    [Benchmark]
    public object[] ObjectCollection() => _objectsCollection.ToArray();

    [Benchmark]
    public int[] IntEnumerable() => _intsEnumerable.ToArray();

    [Benchmark]
    public object[] ObjectEnumerable() => _objectEnumerable.ToArray();

    private static IEnumerable<T> Iterate<T>(IEnumerable<T> source)
    {
        foreach (var item in source) yield return item;
    }
}

Method	Toolchain	Length	Mean	Ratio
IntCollection	\main\corerun.exe	1	18.68 ns	1.00
IntCollection	\pr\corerun.exe	1	15.73 ns	0.84
ObjectCollection	\main\corerun.exe	1	35.72 ns	1.00
ObjectCollection	\pr\corerun.exe	1	31.48 ns	0.88
IntEnumerable	\main\corerun.exe	1	49.37 ns	1.00
IntEnumerable	\pr\corerun.exe	1	48.62 ns	0.98
ObjectEnumerable	\main\corerun.exe	1	86.93 ns	1.00
ObjectEnumerable	\pr\corerun.exe	1	82.68 ns	0.95
IntCollection	\main\corerun.exe	10	21.33 ns	1.00
IntCollection	\pr\corerun.exe	10	18.99 ns	0.92
ObjectCollection	\main\corerun.exe	10	45.16 ns	1.00
ObjectCollection	\pr\corerun.exe	10	42.48 ns	0.94
IntEnumerable	\main\corerun.exe	10	130.02 ns	1.00
IntEnumerable	\pr\corerun.exe	10	126.27 ns	0.96
ObjectEnumerable	\main\corerun.exe	10	261.53 ns	1.00
ObjectEnumerable	\pr\corerun.exe	10	248.10 ns	0.95
IntCollection	\main\corerun.exe	1000	388.00 ns	1.00
IntCollection	\pr\corerun.exe	1000	393.29 ns	1.01
ObjectCollection	\main\corerun.exe	1000	839.89 ns	1.00
ObjectCollection	\pr\corerun.exe	1000	844.79 ns	1.01
IntEnumerable	\main\corerun.exe	1000	5,990.03 ns	1.00
IntEnumerable	\pr\corerun.exe	1000	5,456.53 ns	0.91
ObjectEnumerable	\main\corerun.exe	1000	11,796.91 ns	1.00
ObjectEnumerable	\pr\corerun.exe	1000	11,928.09 ns	1.01

Author:	stephentoub
Assignees:	-
Labels:	area-System.Linq
Milestone:	-