Hi again,
I'm using boolean PropertyMaps to represent subsets of graph vertices
in combination with `GraphView(g, vfilt=Mask).vertices()` for iteration.
I often need the complement of such sets and would like to complement
a mask using `numpy.invert`, for efficiency:
"""
Mask = graph.new_vertex_property('bool')
# this fails
import numpy
notm = numpy.invert(M.ma)
NotMask = graph.new_vertex_property('bool', vals=notm)
# this works, but is O(|V|)
it = imap(lambda x:not Mask[x], graph.vertices())
NotMask = graph.new_vertex_property("bool", vals=it)
"""
The issue seems to be that in boolean PropertyMap internally
uses a PropertyArray of dtype `uint8`, and not `bool`:
In the example above (my graph has 6 nodes), Mask.ma is
PropertyArray([0, 0, 0, 0, 0, 0], dtype=uint8)
So of course, numpy.invert(M.ma) yields
PropertyArray([255, 255, 255, 255, 255, 255], dtype=uint8)
and not, as expected, the array with only 1's.
Is there a reason for using uint8 instead of booleans?
And is there a O(1) operation to invert masks?
Thanks,
Patrick
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