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https://issues.apache.org/jira/browse/MATH-1134?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14051943#comment-14051943
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Gilles commented on MATH-1134:
------------------------------

Phil,

You seem always reluctant to let the code throw a NPE. Although I think that it 
is perfectly fine behaviour to signal a programming error, would you like it 
better if we change the exception type to "MathIllegalStateException"?


> unsafe initialization in BicubicSplineInterpolatingFunction
> -----------------------------------------------------------
>
>                 Key: MATH-1134
>                 URL: https://issues.apache.org/jira/browse/MATH-1134
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 3.3
>            Reporter: Derek Scherger
>            Priority: Minor
>         Attachments: MATH-1134.patch
>
>
> The lazy initialization of the internal array of partialDerivatives in 
> BicubicSplineInterpolatingFunction is not thread safe. If multiple threads 
> call any of the partialDerivative functions concurrently one thread may start 
> the initialization and others will see the array is non-null and assume it is 
> fully initialized. If the internal array of partial derivatives was 
> initialized in the constructor this would not be a problem.
> i.e. the following check in partialDerivative(which, x, y)
>         if (partialDerivatives == null) {
>             computePartialDerivatives();
>         }
> will start the initialization. However in computePartialDerivatives()
>         partialDerivatives = new BivariateFunction[5][lastI][lastJ];
> makes it appear to other threads as the the initialization has completed when 
> it may not have.



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