Proposal for two new samples

[Michael Mirwaldt]

Hi Aleksey,
thank you for your reply.

Sorry that contributing my code takes so long.

I have read http://openjdk.java.net/contribute/ and checked out the 
project and build it locally.
How can I submit my code? Do I just commit it or do I need a new branch?

I have not run a "big" test yet because I miss a linux machine at home 
where I can use "perf".
I will have one very soon.

Best regards,
Michael

Am 27.07.2015 um 23:52 schrieb Aleksey Shipilev:
> Hi Michael,
>
> On 07/28/2015 12:22 AM, Michael Mirwaldt wrote:
>> I would like to add two samples I miss in the jmh repository.
>> They could help jmh users to experience the effect and demonstrate that
>> on their lectures.
>>
>> 1) Branch prediction
>> - it demonstrates how branch prediction/misprediction can lead to
>> better/worse performance.
> Yes, that one is sure missing. This touches on benchmarking methodology
> that tells you might need to feed the benchmark with the data arranged
> in a way you have it in a real world. Therefore, it is a good addendum
> to JMH Samples.
>
>
>> - I could not check whether the branch misses ratio increases.
>> If you are interested I will do so and should observe that with the
>> command line tool perf on a linux machine.
> It would make sense to employ -prof perfnorm or -prof perfasm in the
> explanation for the effect.
>
>
>> 2) Matrix copy
> The cache behavior example is interesting, but I wonder if we can
> somehow construct an example where an innocuously looking *methodology*
> omission backfires a lot. Walking the matrix in one way or the other
> seems to be a code-under-test implementation issue, not the methodology
> quirk?
>
> For example, could the similar cache unfriendliness be demonstrated on
> comparing iteration through HashMap and TreeMap with the same number of
> elements (under the misguided assumption both have the same memory
> footprint)?
>
>> Are the results 'significant in numbers' for you?
> Yes, they are.
>
>> How can I submit my sample code so that you can try it out/review them?
> Sure. The contributions to JMH are governed by the same rules as
> OpenJDK. I see you have the OCA signed and submitted, so we are in
> clear. Show us your code!
>
> Thanks,
> -Aleksey
>