UnsafeAtomicityTest crashes on SPARC

Alan Burlison Alan.Burlison at oracle.com
Wed Aug 31 16:30:36 UTC 2016

On 31/08/2016 14:48, Andrew Haley wrote:

> This is just a lexicographic comparison in Hadoop.  We do have
> misaligned accesses in the new Unsafe, but it's internal.  But I would
> have thought the Hadoop code should use Arrays.compare.

Yes, it probably should but they are focused on squeezing every last 
drop of performance out wherever they can. The misaligned 64-bit word 
hack for lexicographic comparisons makes things a bit faster on the Java 
versions and platforms they concentrate on, which is why they've done 
it. For Java9 that's no longer true any more and pure-Java is the 
fastest way, but of course they aren't using that yet - in fact they 
have only moved up to Java7 fairly recently and are currently working on 
Java8 support:


Alan Burlison

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