Skip to content

Optimize BitOps #667

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
Joy-less wants to merge 1 commit into
base: main
Choose a base branch
from
Open

Optimize BitOps #667

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
36 changes: 20 additions & 16 deletions BitFaster.Caching/BitOps.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -44,7 +44,7 @@ public static uint CeilingPowerOfTwo(uint x)
x |= x >> 16;
return x + 1;
#else
return 1u << -BitOperations.LeadingZeroCount(x - 1);
return BitOperations.RoundUpToPowerOf2(x);
#endif
}

Expand All @@ -66,7 +66,7 @@ internal static ulong CeilingPowerOfTwo(ulong x)
x |= x >> 32;
return x + 1;
#else
return 1ul << -BitOperations.LeadingZeroCount(x - 1);
return BitOperations.RoundUpToPowerOf2(x);
#endif
}

Expand Down Expand Up @@ -113,14 +113,16 @@ 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
}
const uint c1 = 0x_55555555u;
const uint c2 = 0x_33333333u;
const uint c3 = 0x_0F0F0F0Fu;
const uint c4 = 0x_01010101u;

return count;
x -= (x >> 1) & c1;
x = (x & c2) + ((x >> 2) & c2);
x = (((x + (x >> 4)) & c3) * c4) >> 24;

return (int)x;
#else
return BitOperations.PopCount(x);
#endif
Expand All @@ -144,14 +146,16 @@ public static int BitCount(long x)
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
}
const ulong c1 = 0x_55555555_55555555ul;
const ulong c2 = 0x_33333333_33333333ul;
const ulong c3 = 0x_0F0F0F0F_0F0F0F0Ful;
const ulong c4 = 0x_01010101_01010101ul;

x -= (x >> 1) & c1;
x = (x & c2) + ((x >> 2) & c2);
x = (((x + (x >> 4)) & c3) * c4) >> 56;

return count;
return (int)x;
#else
return BitOperations.PopCount(x);
#endif
Expand Down