Affects Version/s: 3.3
Fix Version/s: 3.4
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)
will start the initialization. However in computePartialDerivatives()
partialDerivatives = new BivariateFunction[lastI][lastJ];
makes it appear to other threads as the the initialization has completed when it may not have.