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https://issues.apache.org/jira/browse/LUCENE-7966?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16183010#comment-16183010
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Uwe Schindler edited comment on LUCENE-7966 at 9/27/17 6:14 PM:
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[~dweiss]: The patched class files are actually easier to maintain, as we do
not need Java 9 to compile, no duplicate class files in source folder, or some
fake Java 9 signature files (with questionable license) on bootclasspath (see
my previous branch). This was the main reason to rewrite the class files
instead of maintaining multiple source files. It's just a nice side-effect to
no longer need the delegation methods. So I personally like the patching
approach much more. It would be horrible if we'd require all committers to have
both Java 8 and Java 9 installed!
The question here was just for confirmation and comparison of both approaches,
if they have some side effects.
bq. The slowdown on pic (the most compressible file) is reproducible
[~jpountz]: The one with biggest slowdown on Java 8 is the one with biggest
speedup in Java 9. The reason is quite clear: The Java 8 implementation by
Robert does more checks than the "old" LZ4 implementation (for safety and to be
compatible with new Java 9 impl). But on Java 9 the new method used is an
intrinsic, so we have a huge perf win!
was (Author: thetaphi):
[~dweiss]: The patched class files are actually easier to maintain, as we do
not need Java 9 to compile, no duplicate class files in source folder, or some
fake Java 9 signature files (with questionable license) on bootclasspath (see
my previous branch). This was the main reason to rewrite the class files
instead of maintaining multiple source files. It's just a nice side-effect to
no longer need the delegation methods. So I perosnally like the approach much
more. It would be horrible if we'd require all committers to have both Java 8
and Java 9 installed!
The question here was just for confirmation and comparison of both approaches,
if they have some side effects.
bq. The slowdown on pic (the most compressible file) is reproducible
[~jpountz]: The one with biggest slowdown on Java 8 is the one with biggest
speedup in Java 9. The reason is quite clear: The Java 8 implementation by
Robert does more checks than the "old" LZ4 implementation (for safety and to be
compatible with new Java 9 impl). But on Java 9 the new method used is an
intrinsic, so we have a huge perf win!
> build mr-jar and use some java 9 methods if available
> -----------------------------------------------------
>
> Key: LUCENE-7966
> URL: https://issues.apache.org/jira/browse/LUCENE-7966
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/other, general/build
> Reporter: Robert Muir
> Labels: Java9
> Attachments: LUCENE-7966.patch, LUCENE-7966.patch, LUCENE-7966.patch,
> LUCENE-7966.patch, LUCENE-7966.patch
>
>
> See background: http://openjdk.java.net/jeps/238
> It would be nice to use some of the newer array methods and range checking
> methods in java 9 for example, without waiting for lucene 10 or something. If
> we build an MR-jar, we can start migrating our code to use java 9 methods
> right now, it will use optimized methods from java 9 when thats available,
> otherwise fall back to java 8 code.
> This patch adds:
> {code}
> Objects.checkIndex(int,int)
> Objects.checkFromToIndex(int,int,int)
> Objects.checkFromIndexSize(int,int,int)
> Arrays.mismatch(byte[],int,int,byte[],int,int)
> Arrays.compareUnsigned(byte[],int,int,byte[],int,int)
> Arrays.equal(byte[],int,int,byte[],int,int)
> // did not add char/int/long/short/etc but of course its possible if needed
> {code}
> It sets these up in {{org.apache.lucene.future}} as 1-1 mappings to java
> methods. This way, we can simply directly replace call sites with java 9
> methods when java 9 is a minimum. Simple 1-1 mappings mean also that we only
> have to worry about testing that our java 8 fallback methods work.
> I found that many of the current byte array methods today are willy-nilly and
> very lenient for example, passing invalid offsets at times and relying on
> compare methods not throwing exceptions, etc. I fixed all the instances in
> core/codecs but have not looked at the problems with AnalyzingSuggester. Also
> SimpleText still uses a silly method in ArrayUtil in similar crazy way, have
> not removed that one yet.
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