Use Iterator<T>.TryGetFirst in Enumerable.Any()

[stephentoub]

Enumerable.Any() currently uses TryGetNonEnumeratedCount, comparing the result to 0, and TryGetNonEnumeratedCount uses Iterator<T>.GetCount(onlyIfCheap: true). But this leaves out iterators for which it's not cheap to compute the count; for these, however, we can now benefit from every Iterator<T> providing a TryGetFirst; its found result can be used as the result of Any. This PR inlines TryGetNonEnumeratedCount into Any and then updates its use of Iterator<T> to first use GetCount and then fall back to using TryGetFirst if GetCount is unsuccessful.

Method	Toolchain	Source	Mean	Ratio	Allocated	Alloc Ratio
Any	\main\corerun.exe	0	3.346 ns	1.00	-	NA
Any	\pr\corerun.exe	0	3.277 ns	0.98	-	NA
Any	\main\corerun.exe	1	2.625 ns	1.00	-	NA
Any	\pr\corerun.exe	1	2.315 ns	0.88	-	NA
Any	\main\corerun.exe	2	16.728 ns	1.00	56 B	1.00
Any	\pr\corerun.exe	2	4.154 ns	0.25	-	0.00
Any	\main\corerun.exe	3	13.110 ns	1.00	-	NA
Any	\pr\corerun.exe	3	12.690 ns	0.97	-	NA
Any	\main\corerun.exe	4	14.299 ns	1.00	-	NA
Any	\pr\corerun.exe	4	12.912 ns	0.90	-	NA
Any	\main\corerun.exe	5	3.741 ns	1.00	-	NA
Any	\pr\corerun.exe	5	3.643 ns	0.97	-	NA
Any	\main\corerun.exe	6	11.118 ns	1.00	-	NA
Any	\pr\corerun.exe	6	8.741 ns	0.79	-	NA
Any	\main\corerun.exe	7	47.425 ns	1.00	160 B	1.00
Any	\pr\corerun.exe	7	48.630 ns	1.03	160 B	1.00
Any	\main\corerun.exe	8	66.663 ns	1.00	328 B	1.00
Any	\pr\corerun.exe	8	9.842 ns	0.15	-	0.00
Any	\main\corerun.exe	9	12.304 ns	1.00	-	NA
Any	\pr\corerun.exe	9	17.323 ns	1.40	-	NA
Any	\main\corerun.exe	10	12.027 ns	1.00	40 B	1.00
Any	\pr\corerun.exe	10	10.224 ns	0.84	40 B	1.00
Any	\main\corerun.exe	11	26.032 ns	1.00	96 B	1.00
Any	\pr\corerun.exe	11	14.288 ns	0.55	40 B	0.42
Any	\main\corerun.exe	12	30.752 ns	1.00	104 B	1.00
Any	\pr\corerun.exe	12	15.216 ns	0.49	40 B	0.38
Any	\main\corerun.exe	13	581.665 ns	1.00	520 B	1.00
Any	\pr\corerun.exe	13	195.656 ns	0.34	40 B	0.08
Any	\main\corerun.exe	14	1,405.573 ns	1.00	1576 B	1.00
Any	\pr\corerun.exe	14	285.060 ns	0.20	40 B	0.03
Any	\main\corerun.exe	15	54.888 ns	1.00	96 B	1.00
Any	\pr\corerun.exe	15	47.273 ns	0.86	40 B	0.42
Any	\main\corerun.exe	16	361.296 ns	1.00	512 B	1.00
Any	\pr\corerun.exe	16	173.690 ns	0.48	40 B	0.08
Any	\main\corerun.exe	17	46.332 ns	1.00	168 B	1.00
Any	\pr\corerun.exe	17	46.564 ns	1.01	168 B	1.00
Any	\main\corerun.exe	18	65.017 ns	1.00	336 B	1.00
Any	\pr\corerun.exe	18	14.699 ns	0.23	40 B	0.12
Any	\main\corerun.exe	19	37.565 ns	1.00	96 B	1.00
Any	\pr\corerun.exe	19	23.274 ns	0.62	40 B	0.42

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

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

[MemoryDiagnoser(false)]
[HideColumns("Job", "Error", "StdDev", "Median", "RatioSD")]
public partial class Tests
{
    private IEnumerable<int> _data;

    [Params(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)]
    public int Source { get; set; }

    [GlobalSetup]
    public void Setup()
    {
        IEnumerable<int> data = Source >= 10 ? Iterations(100) : Enumerable.Range(0, 100).ToArray();
        _data = (Source % 10) switch
        {
            0 => data,
            1 => data.Select(i => i),
            2 => data.Where(i => i % 2 == 0).Select(i => i),
            3 => data.Order(),
            4 => data.OrderBy(i => i).Select(i => i),
            5 => data.Skip(20).Take(10),
            6 => data.Reverse(),
            7 => data.SelectMany(i => new int[] { i }),
            8 => data.Distinct(),
            9 => data.Concat(data),
            _ => throw new NotSupportedException()
        };
    }

    [Benchmark]
    public bool Any() => _data.Any();

    private static IEnumerable<int> Iterations(int count)
    {
        for (int i = 0; i < count; i++) yield return i;
    }
}

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Issue Details

---

Enumerable.Any() currently uses TryGetNonEnumeratedCount, comparing the result to 0, and TryGetNonEnumeratedCount uses Iterator<T>.GetCount(onlyIfCheap: true). But this leaves out iterators for which it's not cheap to compute the count; for these, however, we can now benefit from every Iterator<T> providing a TryGetFirst; its found result can be used as the result of Any. This PR inlines TryGetNonEnumeratedCount into Any and then updates its use of Iterator<T> to first use GetCount and then fall back to using TryGetFirst if GetCount is unsuccessful.

Method	Toolchain	Source	Mean	Ratio	Allocated	Alloc Ratio
Any	\main\corerun.exe	0	3.346 ns	1.00	-	NA
Any	\pr\corerun.exe	0	3.277 ns	0.98	-	NA
Any	\main\corerun.exe	1	2.625 ns	1.00	-	NA
Any	\pr\corerun.exe	1	2.315 ns	0.88	-	NA
Any	\main\corerun.exe	2	16.728 ns	1.00	56 B	1.00
Any	\pr\corerun.exe	2	4.154 ns	0.25	-	0.00
Any	\main\corerun.exe	3	13.110 ns	1.00	-	NA
Any	\pr\corerun.exe	3	12.690 ns	0.97	-	NA
Any	\main\corerun.exe	4	14.299 ns	1.00	-	NA
Any	\pr\corerun.exe	4	12.912 ns	0.90	-	NA
Any	\main\corerun.exe	5	3.741 ns	1.00	-	NA
Any	\pr\corerun.exe	5	3.643 ns	0.97	-	NA
Any	\main\corerun.exe	6	11.118 ns	1.00	-	NA
Any	\pr\corerun.exe	6	8.741 ns	0.79	-	NA
Any	\main\corerun.exe	7	47.425 ns	1.00	160 B	1.00
Any	\pr\corerun.exe	7	48.630 ns	1.03	160 B	1.00
Any	\main\corerun.exe	8	66.663 ns	1.00	328 B	1.00
Any	\pr\corerun.exe	8	9.842 ns	0.15	-	0.00
Any	\main\corerun.exe	9	12.304 ns	1.00	-	NA
Any	\pr\corerun.exe	9	17.323 ns	1.40	-	NA
Any	\main\corerun.exe	10	12.027 ns	1.00	40 B	1.00
Any	\pr\corerun.exe	10	10.224 ns	0.84	40 B	1.00
Any	\main\corerun.exe	11	26.032 ns	1.00	96 B	1.00
Any	\pr\corerun.exe	11	14.288 ns	0.55	40 B	0.42
Any	\main\corerun.exe	12	30.752 ns	1.00	104 B	1.00
Any	\pr\corerun.exe	12	15.216 ns	0.49	40 B	0.38
Any	\main\corerun.exe	13	581.665 ns	1.00	520 B	1.00
Any	\pr\corerun.exe	13	195.656 ns	0.34	40 B	0.08
Any	\main\corerun.exe	14	1,405.573 ns	1.00	1576 B	1.00
Any	\pr\corerun.exe	14	285.060 ns	0.20	40 B	0.03
Any	\main\corerun.exe	15	54.888 ns	1.00	96 B	1.00
Any	\pr\corerun.exe	15	47.273 ns	0.86	40 B	0.42
Any	\main\corerun.exe	16	361.296 ns	1.00	512 B	1.00
Any	\pr\corerun.exe	16	173.690 ns	0.48	40 B	0.08
Any	\main\corerun.exe	17	46.332 ns	1.00	168 B	1.00
Any	\pr\corerun.exe	17	46.564 ns	1.01	168 B	1.00
Any	\main\corerun.exe	18	65.017 ns	1.00	336 B	1.00
Any	\pr\corerun.exe	18	14.699 ns	0.23	40 B	0.12
Any	\main\corerun.exe	19	37.565 ns	1.00	96 B	1.00
Any	\pr\corerun.exe	19	23.274 ns	0.62	40 B	0.42

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

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

[MemoryDiagnoser(false)]
[HideColumns("Job", "Error", "StdDev", "Median", "RatioSD")]
public partial class Tests
{
    private IEnumerable<int> _data;

    [Params(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)]
    public int Source { get; set; }

    [GlobalSetup]
    public void Setup()
    {
        IEnumerable<int> data = Source >= 10 ? Iterations(100) : Enumerable.Range(0, 100).ToArray();
        _data = (Source % 10) switch
        {
            0 => data,
            1 => data.Select(i => i),
            2 => data.Where(i => i % 2 == 0).Select(i => i),
            3 => data.Order(),
            4 => data.OrderBy(i => i).Select(i => i),
            5 => data.Skip(20).Take(10),
            6 => data.Reverse(),
            7 => data.SelectMany(i => new int[] { i }),
            8 => data.Distinct(),
            9 => data.Concat(data),
            _ => throw new NotSupportedException()
        };
    }

    [Benchmark]
    public bool Any() => _data.Any();

    private static IEnumerable<int> Iterations(int count)
    {
        for (int i = 0; i < count; i++) yield return i;
    }
}

Author:	stephentoub
Assignees:	-
Labels:	area-System.Linq, tenet-performance
Milestone:	9.0.0