RFR: 8253086: Optimization of removeAll and retainAll of ObservableListWrapper [v4]

[Kevin Rushforth]

On Tue, 22 Sep 2020 07:35:49 GMT, yosbits <github.com+7517141+yososs at openjdk.org> wrote:

>> https://bugs.openjdk.java.net/browse/JDK-8253086
>> 
>> ObservableListWrapper.java
>>  * public boolean removeAll(Collection<?> c)
>> * public boolean retainAll(Collection<?> c)
>> 
>> These two methods use BitSet, but it doesn't make sense.
>> By rewriting to the equivalent behavior that does not use BitSet, it is possible to reduce the CPU load in a wide range
>> of use cases.
>> The test is done with the following command.
>> 
>> * gradle base: test
>> * gradle controls: test
>
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As mentioned in a reply to a comment by @kleopatra , this fix will cause a regression in behavior, and cannot be
integrated in its current form.

A two-pass algorithm is still needed: the first pass collects the elements to be removed, the second pass actually
removes them. While it isn't necessary to use a BitSet to collect the indexes to be removed, that does seems a
reasonable approach. Unless there is a good reason to change it to some other two-pass algorithm, it's probably best to
leave it as-is, in which case this PR and the associated JBS issue can be withdrawn.

-------------

Changes requested by kcr (Lead).

PR: https://git.openjdk.java.net/jfx/pull/305