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From "Ismael Juma (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MATH-230) Implement Sparse Matrix Support
Date Sat, 13 Dec 2008 22:34:44 GMT

    [ https://issues.apache.org/jira/browse/MATH-230?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12656345#action_12656345
] 

Ismael Juma commented on MATH-230:
----------------------------------

After running the test suite a few times, I also got a failure. I should be able to create
a test case that does not involve randomness by adding some code to track puts, gets and removes.
By the way, the reason why the initial tests involved random numbers is precisely for their
ability to find weird corner cases like this (similar to QuickCheck and ScalaCheck, but done
manually). They are not the best way to narrow down the problem though. :)

> Implement Sparse Matrix Support
> -------------------------------
>
>                 Key: MATH-230
>                 URL: https://issues.apache.org/jira/browse/MATH-230
>             Project: Commons Math
>          Issue Type: Improvement
>    Affects Versions: 2.0
>         Environment: N/A
>            Reporter: Sujit Pal
>            Assignee: Luc Maisonobe
>            Priority: Minor
>             Fix For: 2.0
>
>         Attachments: math-230.diff, patch-2.txt, RealMatrixImplPerformanceTest.java,
SparseRealMatrix.java, SparseRealMatrixTest.java
>
>
> I needed a way to deal with large sparse matrices using commons-math RealMatrix, so I
implemented it. The SparseRealMatrixImpl is a subclass of RealMatrixImpl, and the backing
data structure is a Map<Point,Double>, where Point is a struct like inner-class which
exposes two int parameters row and column. I had to make some changes to the existing components
to keep the code for SparseRealMatrixImpl clean. Here are the details.
> 1) RealMatrix.java:
>    - added a new method setEntry(int, int, double) to set data into a matrix
> 2) RealMatrixImpl.java:
>    - changed all internal calls to data[i][j] to getEntry(i,j).
>    - for some methods such as add(), subtract(), premultiply(), etc, there
>      was code that checked for ClassCastException and had two versions,
>      one for a generic RealMatrix and one for a RealMatrixImpl. This has
>      been changed to have only one that operates on a RealMatrix. The 
>      result is something like auto-type casting. So if:
>        RealMatrixImpl.add(RealMatrix) returns a RealMatrixImpl
>        SparseRealMatrixImpl.add(RealMatrix) returns a SparseRealMatrixImpl
> 3) SparseRealMatrixImpl added as a subclass of RealMatrixImpl.
> 4) LUDecompositionImpl changed to use a clone of the passed in RealMatrix
>    instead of its data[][] block, and now it uses clone.getEntry(row,col)
>    calls instead of data[row][col] calls.
> 5) LUDecompositionImpl returned RealMatrixImpl for getL(), getU(), getP()
>    and solve(). It now returns the same RealMatrix impl that is passed 
>    in through its constructor for these methods.
> 6) New test for SparseRealMatrixImpl, mimics the tests in RealMatrixImplTest,
> 7) New static method to create SparseRealMatrixImpl out of a double[][] in
>    MatrixUtils.createSparseRealMatrix().
>    but using SparseRealMatrixImpl.
> 8) Verified that all JUnit tests pass.

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