Where and why to ignore 0 in VI?

[Keep-Passion]

Thank you for sharing your code.
And I found that the codes of vi in skimage and cremi are also based on gala's code.
*gala:https://github.com/janelia-flyem/gala/blob/master/gala/evaluate.py
*skimage: https://github.com/scikit-image/scikit-image/blob/master/skimage/metrics/_variation_of_information.py
*cremi: https://github.com/cremi/cremi_python/blob/master/cremi/evaluation/voi.py
But there is a tiny question: Where and why to ignore 0 in VI?
For your code, gala, you ignore 0 both in gt and pred (Default)
For cremi code, they only ignore 0 in gt, not in pred (Deafult)
For skimage, they did not ignore 0 in gt and pred (Default)
I made a simple comparison below, and i found that different setting will draw out different result. Can you tell what should i do in the task of neuron segmentation? Do i need to ignore 0 label in both gt and pred?