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optimize bitops #802

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a328a64
optimize bitops
May 4, 2026
06d4930
tests
May 4, 2026
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19 changes: 16 additions & 3 deletions BitFaster.Caching.UnitTests/BitOpsTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -88,16 +88,29 @@ public void IntBitCount()
BitOps.BitCount(666).Should().Be(5);
}

[Theory]
[InlineData(0U, 0)]
[InlineData(666U, 5)]
[InlineData(uint.MaxValue, 32)]
public void UIntBitCount(uint input, int count)
{
BitOps.BitCount(input).Should().Be(count);
}

[Fact]
public void LongtBitCount()
{
BitOps.BitCount(666L).Should().Be(5);
}

[Fact]
public void ULongtBitCount()

[Theory]
[InlineData(0UL, 0)]
[InlineData(666UL, 5)]
[InlineData(ulong.MaxValue, 64)]
public void ULongtBitCount(ulong input, int count)
{
BitOps.BitCount(666UL).Should().Be(5);
BitOps.BitCount(input).Should().Be(count);
}
}
}
28 changes: 13 additions & 15 deletions BitFaster.Caching/BitOps.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,8 @@ public static uint CeilingPowerOfTwo(uint x)
x |= x >> 8;
x |= x >> 16;
return x + 1;
#elif NET6_0_OR_GREATER
return BitOperations.RoundUpToPowerOf2(x);
#else
return 1u << -BitOperations.LeadingZeroCount(x - 1);
#endif
Expand All @@ -65,6 +67,8 @@ internal static ulong CeilingPowerOfTwo(ulong x)
x |= x >> 16;
x |= x >> 32;
return x + 1;
#elif NET6_0_OR_GREATER
return BitOperations.RoundUpToPowerOf2(x);
#else
return 1ul << -BitOperations.LeadingZeroCount(x - 1);
#endif
Expand Down Expand Up @@ -113,14 +117,11 @@ public static int BitCount(int x)
public static int BitCount(uint x)
{
#if NETSTANDARD2_0
var count = 0;
while (x != 0)
{
count++;
x &= x - 1; //walking through all the bits which are set to one
}
x -= (x >> 1) & 0x_55555555u;
x = (x & 0x_33333333u) + ((x >> 2) & 0x_33333333u);
x = (((x + (x >> 4)) & 0x_0F0F0F0Fu) * 0x_01010101u) >> 24;

return count;
return (int)x;
#else
return BitOperations.PopCount(x);
#endif
Expand All @@ -141,20 +142,17 @@ public static int BitCount(long x)
/// </summary>
/// <param name="x">The input parameter.</param>
/// <returns>The number of 1 bits.</returns>
// https://stackoverflow.com/questions/2709430/count-number-of-bits-in-a-64-bit-long-big-integer
public static int BitCount(ulong x)
{
#if NETSTANDARD2_0
var count = 0;
while (x != 0)
{
count++;
x &= x - 1; //walking through all the bits which are set to one
}

return count;
x = x - ((x >> 1) & 0x5555555555555555ul);
x = (x & 0x3333333333333333ul) + ((x >> 2) & 0x3333333333333333ul);
return (int)((((x + (x >> 4)) & 0xF0F0F0F0F0F0F0Ful) * 0x101010101010101ul) >> 56);
#else
return BitOperations.PopCount(x);
#endif

}

/// <summary>
Expand Down
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