Skip to content

Optimize Ulid fallback equality check with branchless XOR comparison. #43

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

Merged
Seramis merged 1 commit into from
May 6, 2026
Merged

Optimize Ulid fallback equality check with branchless XOR comparison. #43

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
8 changes: 6 additions & 2 deletions src/ByteAether.Ulid/Ulid.Equatable.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -101,7 +101,11 @@ private static bool EqualsCore(in Ulid left, in Ulid right)
ref var rA = ref Unsafe.As<Ulid, long>(ref Unsafe.AsRef(in left));
ref var rB = ref Unsafe.As<Ulid, long>(ref Unsafe.AsRef(in right));

// Compare 2x 64bit long
return rA == rB && Unsafe.Add(ref rA, 1) == Unsafe.Add(ref rB, 1);
// XOR-compare instead of 2x 64bit long compare with AND
// Branchless XOR-compare is faster (1-3ns vs. 20-25ns)
var xor0 = rA ^ rB;
var xor1 = Unsafe.Add(ref rA, 1) ^ Unsafe.Add(ref rB, 1);

return (xor0 | xor1) == 0;
}
}
Loading