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From: Cecil Westerhof <Cecil@decebal.nl>
Newsgroups: comp.lang.java.programmer
Subject: Re: One code is aggressively optimised, while another not. Why?
Date: Thu, 13 Jul 2017 09:51:51 +0200
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Eric Sosman <esosman@comcast-dot-net.invalid> writes:

> On 7/12/2017 4:07 AM, Cecil Westerhof wrote:
>> I am looking into some performance metrics. I have the following code:
>> [... incomplete code fragments deleted; see up-thread ...]
>>
>> The second code takes about 50% more time to execute. No surprise
>> there. But the first code is aggressively optimised [...]
>>
>> Why the difference?
>
>     Perhaps someone could suggest an answer were the complete
> program made available for inspection.  Hint, hint.

I uploaded the current program to:
    https://github.com/CecilWesterhof/JavaExamples/blob/master/BoxedTest.java

Originally it was to show the risks of using autoboxing, but when
using an integer instead of a long I got this surprising result.

Only with long int I see an improvement in the performance. And quit a
big one.

The output I get on my system is:
    09:02:30: Timing long int    
    09:02:30: took 2.06E+00 seconds.
    09:02:32: took 1.21E-03 seconds.
    09:02:32: took 1.01E-04 seconds.
    09:02:32: took 7.38E-07 seconds.
    09:02:32: took 7.13E-07 seconds.

    09:02:32: Timing long long   
    09:02:32: took 3.06E+00 seconds.
    09:02:35: took 3.05E+00 seconds.
    09:02:38: took 3.79E+00 seconds.
    09:02:42: took 3.84E+00 seconds.
    09:02:46: took 3.81E+00 seconds.

    09:02:50: Timing Long int    
    09:02:50: took 3.46E+01 seconds.
    09:03:24: took 3.75E+01 seconds.
    09:04:02: took 3.62E+01 seconds.
    09:04:38: took 3.62E+01 seconds.
    09:05:14: took 3.97E+01 seconds.

    09:05:54: Timing Long long   
    09:05:54: took 3.61E+01 seconds.
    09:06:30: took 3.69E+01 seconds.
    09:07:07: took 3.65E+01 seconds.
    09:07:43: took 3.66E+01 seconds.
    09:08:20: took 3.75E+01 seconds.

    09:08:57: Timing long Integer
    09:08:57: took 2.63E+01 seconds.
    09:09:24: took 2.49E+01 seconds.
    09:09:49: took 2.57E+01 seconds.
    09:10:14: took 2.52E+01 seconds.
    09:10:40: took 2.49E+01 seconds.

    09:11:05: Timing long Long   
    09:11:05: took 3.63E+01 seconds.
    09:11:41: took 3.67E+01 seconds.
    09:12:18: took 3.41E+01 seconds.
    09:12:52: took 3.39E+01 seconds.
    09:13:26: took 3.41E+01 seconds.

    09:14:00: Timing Long Integer
    09:14:00: took 5.49E+01 seconds.
    09:14:55: took 5.47E+01 seconds.
    09:15:49: took 5.77E+01 seconds.
    09:16:47: took 5.68E+01 seconds.
    09:17:44: took 5.71E+01 seconds.

    09:18:41: Timing Long Long   
    09:18:41: took 6.68E+01 seconds.
    09:19:48: took 6.68E+01 seconds.
    09:20:54: took 6.64E+01 seconds.
    09:22:01: took 6.63E+01 seconds.
    09:23:07: took 7.30E+01 seconds.

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof