Feed an array comprised of non trivial equal numbers (e.g. a 1,000 values of 1.2345) to the Std Deviation and Variance.vi of the Mathematics>>Probability & Statistics palette and look at the standard deviation output using a display format such as that shown below:
You will be surprised to see that the standard deviation is non zero and within the range of the precision for the type (~1E-15).
While this might not be an issue in most use cases, it is still not an optimal result, and suggests that the calculation done in the called DLL is not optimal (it probably uses the standard formula, but because of round-off errors, the outcome is non-zero).
I am posting this in the "bug" category, although it is not strictly speaking one, just to warn unsuspecting users (like me), that dealing with floating point numbers comes with its load of gotchas.
Here is a snippet to experiment with the phenomenon:
Again the display format of the standard deviation indicator needs to be chosen wisely to reveal the round off error.