the L_infinity norm of a finite dimensional vector is just the max of the absolute value of its entries.
The current implementation in ArrayRealVector has a typo:
the += should just be an =.
There is sadly a unit test assuring us that this is the correct behavior (effectively a regression-only test, not a test for correctness).
Worse, the implementation in OpenMapRealVector is not even positive semi-definite:
I would suggest that this method be moved up to the AbstractRealVector superclass and implemented using the sparseIterator():
Unit tests with negative valued vectors would be helpful to check for this kind of thing in the future.