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<p>The implementation of the Foreign Function & Memory API uses
an internal custom linked list to add native resources to a
"memory session" abstraction (things that need to be cleaned up at
a later point).</p>
<p>Linked list is quite critical in our use case because we need
something that has a very fast insertion (in the head), and can
scale gracefully to handle multiple threads.</p>
<p>In our case LinkedList is not good enough (because we want to
deal with concurrent writes ourselves) - but aside from that, note
that, at least looking at the numbers posted in your benchmarks,
it seems that prepending an element to a classic LinkedList is 10x
faster than ArrayList and 5x faster IndexList. Perhaps that's a
case where IndexList has not been fully optimized - but for
prepend-heavy code (and the javac compiler is another one of
those), I think performance of addFirst is the number to look at.</p>
<p>As Tagir said, of course these use cases are very "niche" - and,
at least in my experience, deevelopers in this "niche" tend to
come up with ad-hoc specialized data structures anyways. So the
return of investment for adding another collection type in this
space seems relatively low.<br>
</p>
<p>Maurizio<br>
</p>
<div class="moz-cite-prefix">On 09/07/2022 20:33, Tagir Valeev
wrote:<br>
</div>
<blockquote type="cite" cite="mid:CAE+3fjYgWPT9cZZCCYUN-hHu_s1=8C85zQahbF+07VFCh-gfig@mail.gmail.com">
<div dir="auto">
<div>Note that nobody these days cares about LinkedList.
Use-cases where LinkedList outperforms careful use of
ArrayList or ArrayDeque are next to none. So saying that your
data structure is better than LinkedList is totally not a
reason to add it to JDK. It should be better than ArrayList
and ArrayDeque.</div>
<div dir="auto"><br>
</div>
<div dir="auto">Having a single data structure that provides
list and deque interface is a reasonable idea. However it
would be much simpler to retrofit existing data structure like
ArrayDeque, rather than create a new data structure. Here's an
issue for this:</div>
<div dir="auto"><a href="https://bugs.openjdk.org/browse/JDK-8143850" target="_blank" rel="noreferrer" moz-do-not-send="true" class="moz-txt-link-freetext">https://bugs.openjdk.org/browse/JDK-8143850</a><br>
</div>
<div dir="auto"><br>
</div>
<div dir="auto">There were also discussions to enhance
collections in general, adding more useful methods like
getFirst() or removeLast() to ArrayList, etc. See for details:</div>
<div dir="auto"><a href="https://bugs.openjdk.org/browse/JDK-8266572" moz-do-not-send="true" class="moz-txt-link-freetext">https://bugs.openjdk.org/browse/JDK-8266572</a><br>
</div>
<div dir="auto"><br>
</div>
<div dir="auto">To conclude, the idea of adding one more
collection implementation looks questionable to me. It will
add more confusion when people need to select which collection
fits their needs better. It will require more learning. This
could be justified if there are clear benefits in using it in
real world problems, compared to existing collections. But so
far I don't see the examples of such problems.</div>
<div dir="auto"><br>
</div>
<div dir="auto">With best regards,</div>
<div dir="auto">Tagir Valeev<br>
<br>
<div class="gmail_quote" dir="auto">
<div dir="ltr" class="gmail_attr">сб, 9 июл. 2022 г., 11:22
Rodion Efremov <<a href="mailto:coderodd3@gmail.com" target="_blank" rel="noreferrer" moz-do-not-send="true" class="moz-txt-link-freetext">coderodd3@gmail.com</a>>:<br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">Hello,
<div><br>
</div>
<div>My benchmarking suggests, that, if nothing else, my
IndexedLinkedList outperforms gracefully the
java.util.LinkedList, so the use case should be the
same (List<E> + Deque<E> -interfaces) for
both of the aforementioned data structures.</div>
<div><br>
</div>
<div>Best regards,</div>
<div>rodde</div>
</div>
<div dir="ltr"><br>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sat, Jul 9, 2022 at
11:19 AM Tagir Valeev <<a href="mailto:amaembo@gmail.com" rel="noreferrer
noreferrer" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">amaembo@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="auto">Hello!
<div dir="auto"><br>
</div>
<div dir="auto">Are there real world problems/use
cases where IndexedLinkedList would be preferred
in terms of CPU/memory usage over ArrayList? </div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">сб, 9 июл. 2022
г., 07:18 Rodion Efremov <<a href="mailto:coderodd3@gmail.com" rel="noreferrer noreferrer" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">coderodd3@gmail.com</a>>:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px
0px 0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">Data structure
repo:
<div><a href="https://github.com/coderodde/IndexedLinkedList" rel="noreferrer noreferrer noreferrer" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">https://github.com/coderodde/IndexedLinkedList</a></div>
<div dir="auto"><br>
</div>
Benchmark repo:
<div dir="auto"><a href="https://github.com/coderodde/IndexedLinkedListBenchmark" rel="noreferrer noreferrer noreferrer" target="_blank" moz-do-not-send="true" class="moz-txt-link-freetext">https://github.com/coderodde/IndexedLinkedListBenchmark</a></div>
<div><br>
</div>
<div dir="auto">I have profiled my data structure
and it seems it’s more performant than
java.util.LinkedList or TreeList, if nothing
else.</div>
<div dir="auto"><br>
</div>
<div dir="auto">So, is there any chance of
including IndexedLinkedList to JDK?</div>
<div dir="auto"><br>
</div>
<div dir="auto">Best regards,</div>
<div dir="auto">rodde</div>
</blockquote>
</div>
</blockquote>
</div>
</blockquote>
</div>
</div>
</div>
</blockquote>
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