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Add AVX2 support to IndexOfAnyValues #78863

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Jan 18, 2023
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Add AVX2 support to IndexOfAnyValues #78863

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2 changes: 1 addition & 1 deletion src/libraries/System.Memory/tests/Span/IndexOfAnyValues.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -360,7 +360,7 @@ static int LastIndexOfAnyExceptReferenceImpl(ReadOnlySpan<char> searchSpace, Rea
private static class IndexOfAnyValuesTestHelper
{
private const int MaxNeedleLength = 10;
private const int MaxHaystackLength = 40;
private const int MaxHaystackLength = 100;
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Where does this number come from?

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These are used by the test when running a few million random inputs through the implementation to check random edge cases.
This number should be large enough so that we test all sorts of code paths - e.g. 100 is enough for

// Process the input with 2 Vector256s (32 chars) at a time.
+
// Process the input with 2 Vector256s (32 chars) at a time.
+
// Process the last 1-32 chars with 2 overlapped Vector256s.

so if the "2 Vector256s at a time" step left something broken, we'd catch it.

On the other hand it doesn't make sense to increase it too much as we'd just end up testing fewer variants of short inputs - and there's nothing in the code that would behave fundamentally differently for inputs of 1k vs 10k characters.


private static readonly char[] s_randomAsciiChars;
private static readonly char[] s_randomLatin1Chars;
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