8000 Fix collection-optimized paths for `Batch` by viceroypenguin · Pull Request #965 · morelinq/MoreLINQ · GitHub
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Fix collection-optimized paths for Batch #965

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Merged
merged 9 commits into from
Feb 26, 2023
Merged

Fix collection-optimized paths for Batch #965

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840503d
Fix collection-optimized paths for `Batch`
viceroypenguin Feb 8, 2023
99e0db3
Add test for runtime iteration
viceroypenguin Feb 9, 2023
e69c901
Apply suggestions from code review
viceroypenguin Feb 13, 2023
a394c3c
Correct variable name
viceroypenguin Feb 13, 2023
b83ce23
Improve `Batch` tests further
viceroypenguin Feb 13, 2023
a5fd99b
Merge remote-tracking branch 'origin/master' into batch
viceroypenguin Feb 26, 2023
ce50d7c
Address CR
viceroypenguin Feb 26, 2023
fdcf5af
Remove trailing whitespace
atifaziz Feb 26, 2023
2d49f5a
Comment why enumerating should fail
atifaziz Feb 26, 2023
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16 changes: 16 additions & 0 deletions MoreLinq.Test/BatchTest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -133,6 +133,22 @@ public void BatchEmptySource(SourceKind kind)
var batches = Enumerable.Empty<int>().ToSourceKind(kind).Batch(100);
Assert.That(batches, Is.Empty);
}

[TestCase(SourceKind.BreakingList)]
[TestCase(SourceKind.BreakingReadOnlyList)]
[TestCase(SourceKind.BreakingCollection)]
public void BatchUsesCollectionCountAtIterationTime(SourceKind kind)
{
var list = new List<int> { 1, 2 };
var result = list.AsSourceKind(kind).Batch(3);

list.Add(3);
result.AssertSequenceEqual(new[] { 1, 2, 3 });

list.Add(4);
// should fail trying to enumerate because count is now greater than the batch size
Assert.That(result.Consume, Throws.TypeOf<BreakException>());
}
}
}

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17 changes: 13 additions & 4 deletions MoreLinq.Test/TestExtensions.cs
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Expand Up @@ -88,13 +88,22 @@ internal static IEnumerable<string> GenerateSplits(this string str, params char[
}

internal static IEnumerable<T> ToSourceKind<T>(this IEnumerable<T> input, SourceKind sourceKind) =>
#pragma warning disable IDE0072 // Add missing cases
sourceKind switch
#pragma warning restore IDE0072 // Add missing cases
{
SourceKind.Sequence => input.Select(x => x),
SourceKind.BreakingList => new BreakingList<T>(input.ToList()),
SourceKind.BreakingReadOnlyList => new BreakingReadOnlyList<T>(input.ToList()),
SourceKind.BreakingCollection => new BreakingCollection<T>(input.ToList()),
SourceKind.BreakingReadOnlyCollection => new BreakingReadOnlyCollection<T>(input.ToList()),
var kind => input.ToList().AsSourceKind(kind)
};

internal static IEnumerable<T> AsSourceKind<T>(this List<T> input, SourceKind sourceKind) =>
sourceKind switch
{
SourceKind.Sequence => input.Select(x => x),
SourceKind.BreakingList => new BreakingList<T>(input),
SourceKind.BreakingReadOnlyList => new BreakingReadOnlyList<T>(input),
SourceKind.BreakingCollection => new BreakingCollection<T>(input),
SourceKind.BreakingReadOnlyCollection => new BreakingReadOnlyCollection<T>(input),
_ => throw new ArgumentException(null, nameof(sourceKind))
};
}
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86 changes: 41 additions & 45 deletions MoreLinq/Batch.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,6 @@ namespace MoreLinq
{
using System;
using System.Collections.Generic;
using System.Linq;

static partial class MoreEnumerable
{
Expand Down Expand Up @@ -87,69 +86,66 @@ public static IEnumerable<TResult> Batch<TSource, TResult>(this IEnumerable<TSou
if (size <= 0) throw new ArgumentOutOfRangeException(nameof(size));
if (resultSelector == null) throw new ArgumentNullException(nameof(resultSelector));

switch (source)
return _(); IEnumerable<TResult> _()
{
case ICollection<TSource> { Count: 0 }:
switch (source)
{
return Enumerable.Empty<TResult>();
}
case ICollection<TSource> collection when collection.Count <= size:
{
return _(); IEnumerable<TResult> _()
case ICollection<TSource> { Count: 0 }:
{
break;
}
case ICollection<TSource> collection when collection.Count <= size:
{
var bucket = new TSource[collection.Count];
collection.CopyTo(bucket, 0);
yield return resultSelector(bucket);
break;
}
}
case IReadOnlyCollection<TSource> { Count: 0 }:
{
return Enumerable.Empty<TResult>();
}
case IReadOnlyList<TSource> list when list.Count <= size:
{
return _(); IEnumerable<TResult> _()
case IReadOnlyCollection<TSource> { Count: 0 }:
{
break;
}
case IReadOnlyList<TSource> list when list.Count <= size:
{
var bucket = new TSource[list.Count];
for (var i = 0; i < list.Count; i++)
bucket[i] = list[i];
yield return resultSelector(bucket);
break;
}
}
case IReadOnlyCollection<TSource> collection when collection.Count <= size:
{
return Batch(collection.Count);
}
default:
{
return Batch(size);
}
case IReadOnlyCollection<TSource> collection when collection.Count <= size:
{
size = collection.Count;
goto default;
}
default:
{
TSource[]? bucket = null;
var count = 0;

IEnumerable<TResult> Batch(int size)
{
TSource[]? bucket = null;
var count = 0;
foreach (var item in source)
{
bucket ??= new TSource[size];
bucket[count++] = item;

foreach (var item in source)
{
bucket ??= new TSource[size];
bucket[count++] = item;
// The bucket is fully buffered before it's yielded
if (count != size)
continue;

// The bucket is fully buffered before it's yielded
if (count != size)
continue;
yield return resultSelector(bucket);

yield return resultSelector(bucket);
bucket = null;
count = 0;
}

bucket = null;
count = 0;
}
// Return the last bucket with all remaining elements
if (count > 0)
{
Array.Resize(ref bucket, count);
yield return resultSelector(bucket);
}

// Return the last bucket with all remaining elements
if (count > 0)
{
Array.Resize(ref bucket, count);
yield return resultSelector(bucket);
break;
}
}
}
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