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From Adam Roberts <AROBE...@uk.ibm.com>
Subject BytesToBytes and unaligned memory
Date Fri, 15 Apr 2016 14:01:09 GMT
Hi, I'm testing Spark 2.0.0 on various architectures and have a question, 
are we sure if 
core/src/test/java/org/apache/spark/unsafe/map/AbstractBytesToBytesMapSuite.java 
really is attempting to use unaligned memory access (for the 
BytesToBytesMapOffHeapSuite tests specifically)?

Our JDKs on zSystems for example return false for the 
java.nio.Bits.unaligned() method and yet if I skip this check and add 
s390x to the supported architectures (for zSystems), all thirteen tests 
here pass. 

The 13 tests here all fail as we do not pass the unaligned requirement 
(but perhaps incorrectly):
core/src/test/java/org/apache/spark/unsafe/map/BytesToBytesMapOffHeapSuite.java 
and I know the unaligned checking is at 
common/unsafe/src/main/java/org/apache/spark/unsafe/Platform.java

Either our JDK's method is returning false incorrectly or this test isn't 
using unaligned memory access (so the requirement is invalid), there's no 
mention of alignment in the test itself.

Any guidance would be very much appreciated, cheers


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