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Improve throughput of Enumerable.Contains for default comparer #25097
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When no comparer or a null comparer is specified to Enumerable.Contains with a non-collection enumerable, `EqualityComparer<TSource>.Default` is used. However, with recent improvements to the JIT around devirtualization and inlining of `EqualityComparer<TSource>.Default`, we can do much better for this case by having a loop dedicated to the comparer==null case. For an enumerable of ints, this speeds up Contains in my measurements by up to 33% (which logically makes sense, as we're effectively eliminating one of three interface calls invoked per element).
JonHanna
approved these changes
Nov 7, 2017
| if (source == null) | ||
| { | ||
| throw Error.ArgumentNull(nameof(source)); | ||
| } | ||
|
|
||
| foreach (TSource element in source) | ||
| if (comparer == null) |
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Would it be worth catching explicitly passed EqualityComparer<TSource>.Default too?
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That's pretty much what I'm wondering. I would guess it would be more common with direct collection operations than with linq to always pass in a comparer and have Default as the default, but that's only a guess.
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I'm not going to right now. Other than size increase, this change doesn't penalize any cases (e.g. it's using a branch that's already there). Adding such a check in theory could negatively impact other cases, even if it might be negligible.
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LGTM too. |
danmoseley
approved these changes
Nov 8, 2017
Dotnet-GitSync-Bot
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…otnet#25097) This was removed accidentally as part of overhauling the async infrastructure in 2.1. VS depends on it for some task tracking logic. Signed-off-by: dotnet-bot <[email protected]>
stephentoub
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…25097) This was removed accidentally as part of overhauling the async infrastructure in 2.1. VS depends on it for some task tracking logic. Signed-off-by: dotnet-bot <[email protected]>
picenka21
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…t/corefx#25097) When no comparer or a null comparer is specified to Enumerable.Contains with a non-collection enumerable, `EqualityComparer<TSource>.Default` is used. However, with recent improvements to the JIT around devirtualization and inlining of `EqualityComparer<TSource>.Default`, we can do much better for this case by having a loop dedicated to the comparer==null case. For an enumerable of ints, this speeds up Contains in my measurements by up to 33% (which logically makes sense, as we're effectively eliminating one of three interface calls invoked per element). Commit migrated from dotnet/corefx@4cc7cd6
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When no comparer or a null comparer is specified to Enumerable.Contains with a non-collection enumerable,
EqualityComparer<TSource>.Defaultis used. However, with recent improvements to the JIT around devirtualization and inlining ofEqualityComparer<TSource>.Default, we can do much better for this case by having a loop dedicated to the comparer==null case. For an enumerable of ints, this speeds up Contains in my measurements by up to 33% (which logically makes sense, as we're effectively eliminating one of three interface calls invoked per element).cc: @VSadov, @OmarTawfik, @AndyAyersMS