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Update DensePartialSortBy to use NullKeyDictionary #500

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merged 2 commits into from
Aug 25, 2023
Merged

Update DensePartialSortBy to use NullKeyDictionary #500

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22d65fb
Update `DensePartialSortBy` to use `NullKeyDictionary`
viceroypenguin Aug 25, 2023
b20cd66
Add tests for `DensePartialSort` stability
viceroypenguin Aug 25, 2023
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16 changes: 9 additions & 7 deletions Source/SuperLinq.Async/DensePartialSort.cs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,6 @@
namespace SuperLinq.Async;
using SuperLinq.Collections;

namespace SuperLinq.Async;

public static partial class AsyncSuperEnumerable
{
Expand Down Expand Up @@ -249,37 +251,37 @@ public static IAsyncEnumerable<TSource> DensePartialSortBy<TSource, TKey>(
static async IAsyncEnumerable<TSource> Core(IAsyncEnumerable<TSource> source, int count, Func<TSource, TKey> keySelector, IComparer<TKey> comparer, [EnumeratorCancellation] CancellationToken cancellationToken = default)
{
var top = new SortedSet<TKey>(comparer);
var dic = new Dictionary<(TKey Key, int Index), List<TSource>>(count);
var dic = new NullKeyDictionary<TKey, List<TSource>>(count);

await foreach (var item in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
var key = keySelector(item);
if (top.TryGetValue(key, out var oKey))
{
dic[(oKey, 1)].Add(item);
dic[oKey].Add(item);
continue;
}

if (top.Count < count)
{
_ = top.Add(key);
dic[(key, 1)] = new() { item, };
dic[key] = new() { item, };
continue;
}

var max = Debug.AssertNotNull(top.Max);
if (comparer.Compare(key, max) > 0)
continue;

_ = dic.Remove((max, 1));
_ = dic.Remove(max);
_ = top.Remove(max);
_ = top.Add(key);
dic[(key, 1)] = new() { item, };
dic[key] = new() { item, };
}

foreach (var entry in top)
{
foreach (var i in dic[(entry, 1)])
foreach (var i in dic[entry])
yield return i;
}
}
Expand Down
4 changes: 4 additions & 0 deletions Source/SuperLinq/Collections/NullKeyDictionary.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,10 @@ public NullKeyDictionary(IEqualityComparer<TKey>? comparer)
: base(comparer: ValueTupleEqualityComparer.Create(comparer))
{ }

public NullKeyDictionary(int count)
: base(count, comparer: ValueTupleEqualityComparer.Create<TKey>(default))
{ }

public TValue this[TKey key]
{
get => this[ValueTuple.Create(key)];
Expand Down
16 changes: 9 additions & 7 deletions Source/SuperLinq/DensePartialSort.cs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,6 @@
namespace SuperLinq;
using SuperLinq.Collections;

namespace SuperLinq;

public static partial class SuperEnumerable
{
Expand Down Expand Up @@ -249,37 +251,37 @@ public static IEnumerable<TSource> DensePartialSortBy<TSource, TKey>(
static IEnumerable<TSource> Core(IEnumerable<TSource> source, int count, Func<TSource, TKey> keySelector, IComparer<TKey> comparer)
{
var top = new SortedSet<TKey>(comparer);
var dic = new Dictionary<(TKey Key, int Index), List<TSource>>(count);
var dic = new NullKeyDictionary<TKey, List<TSource>>(count);

foreach (var item in source)
{
var key = keySelector(item);
if (top.TryGetValue(key, out var oKey))
{
dic[(oKey, 1)].Add(item);
dic[oKey].Add(item);
continue;
}

if (top.Count < count)
{
_ = top.Add(key);
dic[(key, 1)] = new() { item, };
dic[key] = new() { item, };
continue;
}

var max = Debug.AssertNotNull(top.Max);
if (comparer.Compare(key, max) > 0)
continue;

_ = dic.Remove((max, 1));
_ = dic.Remove(max);
_ = top.Remove(max);
_ = top.Add(key);
dic[(key, 1)] = new() { item, };
dic[key] = new() { item, };
}

foreach (var entry in top)
{
foreach (var i in dic[(entry, 1)])
foreach (var i in dic[entry])
yield return i;
}
}
Expand Down
39 changes: 39 additions & 0 deletions Tests/SuperLinq.Async.Test/DensePartialSortByTest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -64,4 +64,43 @@ public async Task DensePartialSortWithComparer()
await sorted.Select(e => e.Key[0])
.AssertSequenceEqual('A', 'A', 'C', 'C', 'E', 'E');
}

[Fact]
public async Task DensePartialSortByIsStable()
{
await using var list = new[]
{
(key: 5, text: "1"),
(key: 5, text: "2"),
(key: 4, text: "3"),
(key: 4, text: "4"),
(key: 3, text: "5"),
(key: 3, text: "6"),
(key: 2, text: "7"),
(key: 2, text: "8"),
(key: 1, text: "9"),
(key: 1, text: "10"),
}.AsTestingSequence(maxEnumerations: 5);

var stableSort = new[]
{
(key: 1, text: "9"),
(key: 1, text: "10"),
(key: 2, text: "7"),
(key: 2, text: "8"),
(key: 3, text: "5"),
(key: 3, text: "6"),
(key: 4, text: "3"),
(key: 4, text: "4"),
(key: 5, text: "1"),
(key: 5, text: "2"),
};

for (var i = 1; i <= 5; i++)
{
var sorted = list.DensePartialSortBy(i, x => x.key);
await sorted.AssertSequenceEqual(
stableSort.Take(i * 2));
}
}
}
41 changes: 41 additions & 0 deletions Tests/SuperLinq.Async.Test/DensePartialSortTest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -56,4 +56,45 @@ await xs
.Select(s => s[0])
.AssertSequenceEqual('A', 'A', 'C', 'C', 'E', 'E');
}

[Fact]
public async Task DensePartialSortIsStable()
{
await using var list = new[]
{
(key: 5, text: "1"),
(key: 5, text: "2"),
(key: 4, text: "3"),
(key: 4, text: "4"),
(key: 3, text: "5"),
(key: 3, text: "6"),
(key: 2, text: "7"),
(key: 2, text: "8"),
(key: 1, text: "9"),
(key: 1, text: "10"),
}.AsTestingSequence(maxEnumerations: 5);

var stableSort = new[]
{
(key: 1, text: "9"),
(key: 1, text: "10"),
(key: 2, text: "7"),
(key: 2, text: "8"),
(key: 3, text: "5"),
(key: 3, text: "6"),
(key: 4, text: "3"),
(key: 4, text: "4"),
(key: 5, text: "1"),
(key: 5, text: "2"),
};

var comparer = Comparer<(int key, string text)>.Create((a, b) => a.key.CompareTo(b.key));

for (var i = 1; i <= 5; i++)
{
var sorted = list.DensePartialSort(i, comparer);
await sorted.AssertSequenceEqual(
stableSort.Take(i * 2));
}
}
}
39 changes: 39 additions & 0 deletions Tests/SuperLinq.Test/DensePartialSortByTest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -64,4 +64,43 @@ public void DensePartialSortWithComparer()
.Select(e => e.Key[0])
.AssertSequenceEqual('A', 'A', 'C', 'C', 'E', 'E');
}

[Fact]
public void DensePartialSortByIsStable()
{
using var list = new[]
{
(key: 5, text: "1"),
(key: 5, text: "2"),
(key: 4, text: "3"),
(key: 4, text: "4"),
(key: 3, text: "5"),
(key: 3, text: "6"),
(key: 2, text: "7"),
(key: 2, text: "8"),
(key: 1, text: "9"),
(key: 1, text: "10"),
}.AsTestingSequence(maxEnumerations: 5);

var stableSort = new[]
{
(key: 1, text: "9"),
(key: 1, text: "10"),
(key: 2, text: "7"),
(key: 2, text: "8"),
(key: 3, text: "5"),
(key: 3, text: "6"),
(key: 4, text: "3"),
(key: 4, text: "4"),
(key: 5, text: "1"),
(key: 5, text: "2"),
};

for (var i = 1; i <= 5; i++)
{
var sorted = list.DensePartialSortBy(i, x => x.key);
sorted.AssertSequenceEqual(
stableSort.Take(i * 2));
}
}
}
41 changes: 41 additions & 0 deletions Tests/SuperLinq.Test/DensePartialSortTest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -56,4 +56,45 @@ public void DensePartialSortWithComparer()
.Select(s => s[0])
.AssertSequenceEqual('A', 'A', 'C', 'C', 'E', 'E');
}

[Fact]
public void DensePartialSortIsStable()
{
using var list = new[]
{
(key: 5, text: "1"),
(key: 5, text: "2"),
(key: 4, text: "3"),
(key: 4, text: "4"),
(key: 3, text: "5"),
(key: 3, text: "6"),
(key: 2, text: "7"),
(key: 2, text: "8"),
(key: 1, text: "9"),
(key: 1, text: "10"),
}.AsTestingSequence(maxEnumerations: 5);

var stableSort = new[]
{
(key: 1, text: "9"),
(key: 1, text: "10"),
(key: 2, text: "7"),
(key: 2, text: "8"),
(key: 3, text: "5"),
(key: 3, text: "6"),
(key: 4, text: "3"),
(key: 4, text: "4"),
(key: 5, text: "1"),
(key: 5, text: "2"),
};

var comparer = Comparer<(int key, string text)>.Create((a, b) => a.key.CompareTo(b.key));

for (var i = 1; i <= 5; i++)
{
var sorted = list.DensePartialSort(i, comparer);
sorted.AssertSequenceEqual(
stableSort.Take(i * 2));
}
}
}