What about a Spliterator based on List.subList() method? While the
specification of List.subList() does not guarantee any specific behavior
when underlying list is structurally modified, the implementations (at
least implementations in JDK based on AbstractList) do have a fail-fast
behavior and there's a chance other implementations too.
Regards, Peter
On 03/07/2016 11:08 AM, Paul Sandoz wrote:
Hi Michael,
It could, stay tuned for some possible action on this.
This is something we did discuss a while ago [1]. At the time we thought most
List implementations would override so did not bother, and admittedly with the
frenzy of all other stuff got de-prioritized. But, perhaps we underestimated
the integration with existing libraries?
To do that we would need to adjust the specification of the default behaviour
which would also adjust the fail-fast behaviour as Tagir points out (which may
be a reasonable compromise in the case, it should be possible to detect certain
co-mod cases)
Paul.
[1]
http://mail.openjdk.java.net/pipermail/lambda-libs-spec-experts/2013-May/001770.html
<http://mail.openjdk.java.net/pipermail/lambda-libs-spec-experts/2013-May/001770.html>
On 7 Mar 2016, at 10:02, Michael Hixson <michael.hix...@gmail.com> wrote:
The default List.spliterator() is iterator-based. Could this be
improved for random access lists, using List.get(int) to fetch
elements instead of List.iterator()?
I think it could improve most on Spliterator.trySplit(). The current
implementation allocates a new array for split-off elements. I see
almost twice the throughput from list.parallelStream().forEach(...)
with a custom get(int)-based implementation over the default one.
For example, instead of this:
default Spliterator<E> spliterator() {
return Spliterators.spliterator(this, Spliterator.ORDERED);
}
I'm suggesting something like this:
default Spliterator<E> spliterator() {
return (this instanceof RandomAccess)
? Spliterators.randomAccessListSpliterator(this)
: Spliterators.spliterator(this, Spliterator.ORDERED);
}
where randomAccessListSpliterator is new code that looks a lot like
Spliterators.ArraySpliterator.
-Michael
