Re: [january-dev] clone() vs System.arraycopy

[Jonah Graham <jonah@xxxxxxxxxxxxxxxx>]

A timely reminder, now that the 2.1 release is out I have requested
conversion to JIPP:
https://bugs.eclipse.org/bugs/show_bug.cgi?id=526133
~~~
Jonah Graham
Kichwa Coders Ltd.
www.kichwacoders.com


On 17 October 2017 at 11:53,  <Peter.Chang@xxxxxxxxxxxxx> wrote:
>
>
> Well, once we move to a JIPP then we can integrate the micro benchmarking
> and end these “optimisations” ;-) Well, at least for one JVM.
>
>
>
> Peter
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> From: january-dev-bounces@xxxxxxxxxxx
> [mailto:january-dev-bounces@xxxxxxxxxxx] On Behalf Of Matthew Gerring
> Sent: 17 October 2017 11:49
> To: Filik, Jacob (DLSLtd,RAL,LSCI) <Jacob.Filik@xxxxxxxxxxxxx>
> Cc: january developer discussions <january-dev@xxxxxxxxxxx>
> Subject: Re: [january-dev] clone() vs System.arraycopy
>
>
>
> Thanks for reading that. He also says:
>
>
>
> "Oops, it seems that once the array becomes longer, the performance of the
> two is almost equal! Infact, the cloning seems marginally faster. Aren't you
> glad that you have not changed all your code yet?"
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>
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> :)
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>
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> On 17 October 2017 at 11:45, <Jacob.Filik@xxxxxxxxxxxxx> wrote:
>
> I have only skimmed the article but he concludes:
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>
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> This leads me to conclude that the only reason why Paul's test seemed so
> much faster was because he picked a byte[] size that was small enough that
> the actual copying was dwarfed by the two if statements. Using clone() for
> copying arrays is less code and the performance difference is, as we saw,
> only significant for tiny arrays. I think that in future I will rather use
> clone() than System.arrayCopy().
>
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> From: january-dev-bounces@xxxxxxxxxxx
> [mailto:january-dev-bounces@xxxxxxxxxxx] On Behalf Of Matthew Gerring
> Sent: 17 October 2017 11:35
> To: january developer discussions <january-dev@xxxxxxxxxxx>
> Subject: [january-dev] clone() vs System.arraycopy
>
>
>
> Hello,
>
>
>
> January uses clone() quite a bit when duplicating large primitive arrays.
> For one of many instances see FloatDataset:
>
> odata = data = dataset.data.clone()
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>
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> However System.arraycopy is ~5x faster according to:
>
> http://www.javaspecialists.co.za/archive/Issue124.html
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> Are there any plans to migrate from clone to arraycopy? Or do I have to
> submit a PR to do that? I might ask one of the team here to submit that
> change if you agree, please let me know you thoughts.
>
>
>
> Matt
>
>
>
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