On 03/13/2014 12:49 PM, Paul Sandoz wrote: > On Mar 13, 2014, at 1:19 PM, Andrew Haley <a...@redhat.com> wrote: >> On 03/13/2014 11:57 AM, Paul Sandoz wrote: >>> Now i am in two minds to whether to add ByteBuffer.compareUnsigned or add >>> Arrays.compareUnsigned. >>> >>> An explosion of methods on Arrays for all types (plus to/from versions) >>> would be annoying. >> >> Surely it's a no brainer? All we have to do is add the intrinsics for >> ByteBuffers, then we get fast ByteBuffers and fast array comparisons too. >> I don't see the problem. > > For byte[] comparison, I don't think optimal long access is > sufficient on it's own due to alignment issues. It would be nice if > we can avoid burdening users with alignment issues to ensure the > main comparison loop is efficient.
But alignment issues are a feature of the hardware, not of software. The problem right now is that ByteBuffers use a byte-by-byte comparison of longs, even when it isn't needed, because there aren't the intrinsics. > A quick solution is to leverage Unsafe within a > ByteBuffer.compareUnsigned method. In fact i believe Unsafe could be > used (as Aleksey says in [1]) for put/get as well, which i presume > is likely to be much easier/quicker to implement. Might be a good > first step until a more superior intrinsics solution is implemented? I still don't get it, sorry. What can Unsafe do that ByteBuffer intrinsics can't do? Andrew.
