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https://issues.apache.org/jira/browse/MATH-1170?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gilles resolved MATH-1170.
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Resolution: Incomplete
Old issue, no patch, not discussed on the ML.
> Add more in-place operations to RealMatrix and RealVector
> ---------------------------------------------------------
>
> Key: MATH-1170
> URL: https://issues.apache.org/jira/browse/MATH-1170
> Project: Commons Math
> Issue Type: Wish
> Reporter: Brian
> Priority: Minor
>
> It would be nice if for some methods of RealMatrix and RealVector there were
> in-place versions of the methods - that would use the existing structures
> rather than creating new ones. In some situations it might be more efficient
> to use the same vector instead of creating many temporary ones each time
> which then have to be garbage collected, so it would be nice to provide the
> option.
> An example of a method that could benefit from in-place versions:
> RealVector.add.
> There was also a question on stack overflow about this for matrix operations:
> http://stackoverflow.com/questions/20529484/performing-in-place-calculations-with-commons-maths-realmatrix
> There is also a lot of precedents for this kind of behavior, in other
> languages.
> In other languages, this is sometimes handled behind the scenes - when a
> self-assignment is found, a new variable is not created - in order to improve
> performance. E.g., some functional languages perform such optimizations
> behind the scenes, and it is used in MATLAB:
> http://blogs.mathworks.com/loren/2007/03/22/in-place-operations-on-data/
> http://undocumentedmatlab.com/blog/internal-matlab-memory-optimizations
> In some ways directly providing the option for in-place operations is
> preferable because then we could control when it is applied. It could be
> used where appropriate within the internals of other methods as well.
> Similarly there is also a convention in Ruby to have a special version of a
> method, marked with an exclamation point to indicate it is "dangerous" -
> usually meaning it changes its input - so-called "bang methods". Many of
> these are built into the core Ruby, e.g., sort/sort! for arrays,
> upcase/upcase!, chomp/chomp!, and reverse/reverse! for strings.
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