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Re: stream concat distinct indeterministic

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On 2/15/2016 3:54 PM, Philipp Kraus wrote:
> Am Montag, 15. Februar 2016 17:30:23 UTC+1 schrieb Arne Vajhøj:
>> On 2/15/2016 11:08 AM, Philipp Kraus wrote:
>>> I run Stream.concat to concat two streams. These two streams are
>>> "stream" and use a flatMap call. After the concat I run distinct() to
>>> create an unique stream of elements, but I get an indeterministic
>>> behaviour of my concated stream, so my question is how can I create a
>>> concated and distinct stream?
>>
>> Docs for distinct says:
>>
>> "For ordered streams, the selection of distinct elements is stable (for
>> duplicated elements, the element appearing first in the encounter order
>> is preserved.) For unordered streams, no stability guarantees are made."
>>
>> so I would guess that you would need to do .sorted().distinct() instead
>> of just .distinct().
>
> Thanks, this seems to be working, I have added a compareTo (overload) and run sorted() before distinct().

     Let's review for a moment.  From bits and pieces of several posts,
it seems you began with

	Stream.concat(str1, str2).distinct().count();

... and reported that the same str1/2 produced different counts in
different runs.  Now you've changed to

	Stream.concat(str1, str2).sorted().distinct().count();

... which shouldn't ("shouldn't") change anything, yet you now report
that everything appears to be working.

     Except, of course, that there's no obvious reason why the original
pipeline would misbehave, and no obvious reason why sorted() should make
any difference (there are exactly as many elements in ACDB as in ABCD).
So I *strongly* encourage you not to let the matter rest, but to look
deeper and see what's really going on.

     You may have uncovered a serious bug in the streams framework --
or you may have made a slip-up elsewhere.  The former is possible, but
to me the latter seems far more likely.

     For the last time: SSCCE?  <http://www.sscce.org/>

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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stream concat distinct indeterministic Philipp Kraus <philipp.kraus.flashpixx@gmail.com> - 2016-02-15 08:08 -0800
  Re: stream concat distinct indeterministic Arne Vajhøj <arne@vajhoej.dk> - 2016-02-15 11:30 -0500
    Re: stream concat distinct indeterministic Philipp Kraus <philipp.kraus.flashpixx@gmail.com> - 2016-02-15 12:54 -0800
      Re: stream concat distinct indeterministic Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-15 16:13 -0500
        Re: stream concat distinct indeterministic Martin Gregorie <martin@address-in-sig.invalid> - 2016-02-15 21:58 +0000
          Re: stream concat distinct indeterministic Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-15 17:45 -0500
            Re: stream concat distinct indeterministic Martin Gregorie <martin@address-in-sig.invalid> - 2016-02-15 23:29 +0000
              Re: stream concat distinct indeterministic Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-16 07:47 -0500
        Re: stream concat distinct indeterministic Arne Vajhøj <arne@vajhoej.dk> - 2016-02-15 21:45 -0500
  Re: stream concat distinct indeterministic Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-15 11:38 -0500
    Re: stream concat distinct indeterministic Philipp Kraus <philipp.kraus.flashpixx@gmail.com> - 2016-02-15 09:05 -0800
      Re: stream concat distinct indeterministic Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-15 14:08 -0500
      Re: stream concat distinct indeterministic Andreas Leitgeb <avl@logic.at> - 2016-02-16 18:40 +0000

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