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From Mark Thomas <ma...@apache.org>
Subject Re: svn commit: r1166099 - /commons/proper/math/trunk/src/main/java/org/apache/commons/math/linear/LUDecompositionImpl.java
Date Wed, 07 Sep 2011 12:16:03 GMT
On 07/09/2011 12:49, Gilles Sadowski wrote:
> On Wed, Sep 07, 2011 at 11:39:37AM +0100, Mark Thomas wrote:
>> On 07/09/2011 11:34, erans@apache.org wrote:
>>> Author: erans
>>> Date: Wed Sep  7 10:34:49 2011
>>> New Revision: 1166099
>>>
>>> URL: http://svn.apache.org/viewvc?rev=1166099&view=rev
>>> Log:
>>> Added "final".
>>> Moved declaration of "sum" where it is used.
>>
>> You might want to re-consider that. I suspect sum was declared outside
>> of the inner loops to save allocating memory for a new double on every
>> iteration of the loop. It may be worth moving the declaration outside
>> the outer loop too.
> 
> Reducing scope makes for clearer code and can lead to _more_ optimized code.

Cleaner code, certainly.

As far as optimisation goes I'm not so sure with a primitive. On further
research it looks like the performance should be identical. For an
"interesting" discussion on what exactly is going on I found this:
http://www.javalobby.org/java/forums/t16730.html?start=0

Mark

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