Graph Isomorphism with VertexPropertyMap of type long

Bug reports:

Informations

• graph-tool version: 2.31 (commit 8561bac9, Fri Mar 27 23:59:57 2020 +0100)
• System: Debian 10 / 5.4.0-0.bpo.4-amd64 / Python version 3.7.3

Bug description

I want to compute an isomorphism between two graph using an invariant. This does not work if the type of the VertexPropertyMap is long (while it works for int or bool).

Reproducible example (may not be minimal)

import graph_tool

# Create g
g: graph_tool.Graph = graph_tool.Graph()
g.add_vertex(3)
g.vp.prop_int = g.new_vertex_property('int')
g.vp.prop_long = g.new_vertex_property('long')

g.vp.prop_int.get_array()[:] = [3, 1, 2]
g.vp.prop_long.get_array()[:] = [2**32, 2**32-1, 2**32-5]

g.add_edge_list([(0, 1), (1, 2)])

# Create g2
g2: graph_tool.Graph = graph_tool.Graph()
g2.add_vertex(3)
g2.vp.prop_int = g2.new_vertex_property('int')
g2.vp.prop_long = g2.new_vertex_property('long')

g2.vp.prop_int.get_array()[:] = [3, 1, 2]
g2.vp.prop_long.get_array()[:] = [2**32, 2**32-1, 2**32-5]

g2.add_edge_list([(0, 1), (1, 2)])


# Works as expected
graph_tool.topology.isomorphism(g, g2, vertex_inv1=g.vp.prop_int, vertex_inv2=g2.vp.prop_int)

# This fails:
graph_tool.topology.isomorphism(g, g2, vertex_inv1=g.vp.prop_long, vertex_inv2=g2.vp.prop_long)

Python error

MemoryError                               Traceback (most recent call last)
<ipython-input-34-0535769d768c> in <module>
----> 1 graph_tool.topology.isomorphism(g1, g2, vertex_inv1=g1.vp.prop_long, vertex_inv2=g2.vp.prop_long)

/usr/lib/python3/dist-packages/graph_tool/topology/__init__.py in isomorphism(g1, g2, vertex_inv1, vertex_inv2, isomap)
    624                              _prop("v", g2, vertex_inv2),
    625                              inv_max,
--> 626                              _prop("v", g1, imap))
    627     if isomap:
    628         return iso, imap

MemoryError: