On Sat, 29 Jan 2022 16:31:43 GMT, Tagir F. Valeev <tval...@openjdk.org> wrote:
> See the bug description for details. > > I propose a simple solution. Let's allow ArraySpliterator to be non-SIZED and > report artificial estimatedSize(), much bigger than the real one. This will > allow AbstractSpliterator and IteratorSpliterator to produce prefix whose > size is comparable to Long.MAX_VALUE (say, starting with Long.MAX_VALUE/2), > and this will enable further splitting of the prefix. This change will > drastically improve parallel streaming for affected streams of size <= 1024 > and significantly improve for streams of size 1025..20000. The cost is > higher-grained splitting for huge streams of unknown size. This might add a > minor overhead for such scenarios which, I believe, is completely tolerable. > > No public API changes are necessary, sequential processing should not be > affected, except an extra field in ArraySpliterator which increases a > footprint by 8 bytes. > > I added a simple test using an artificial collector to ensure that at least > two non-empty parts are created when parallelizing Stream.iterate source. > More testing ideas are welcome. This pull request has now been integrated. Changeset: 4cc8eccf Author: Tagir F. Valeev <tval...@openjdk.org> URL: https://git.openjdk.java.net/jdk/commit/4cc8eccfcadf5d3edc31809ead2dd6554c7cca4b Stats: 212 lines in 3 files changed: 178 ins; 0 del; 34 mod 8280915: Better parallelization for AbstractSpliterator and IteratorSpliterator when size is unknown Reviewed-by: psandoz ------------- PR: https://git.openjdk.java.net/jdk/pull/7279
