[Numpy-discussion] Problem with absolute value

Hameer Abbasi einstein.edison at gmail.com
Wed Jul 3 11:07:52 EDT 2019


It turns out you're running into a bit-error. In general, the two's complement of -2 ** (n-1) with the bit-length being limited to n bits is itself... No way around that. And integers don't set hardware exceptions so checking for errors like these is hard as well.

TL;DR: It's an error with how the integer is stored in memory and how you're running out of space.

Hameer Abbasi

On 03.07.19, 17:03, "NumPy-Discussion on behalf of Nicolas Rougier" <numpy-discussion-bounces+einstein.edison=gmail.com at python.org on behalf of Nicolas.Rougier at inria.fr> wrote:

    I’m a bit surprised with the following code:
    >>> import numpy as np
    >>> np.seterr(all='warn')
    >>> Z = np.array([-128], dtype=np.byte)
    >>> print(np.abs(Z))
    Obviously, it does not return the absolute value and I get no warning.
    Is it something expected ? (numpy 1.16.4, python 3.7.3)
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