wehub-resource-sync
70 lines
1.4 KiB
Python
70 lines
1.4 KiB
Python
"""Generators for some lattice hypergraphs.
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All the functions in this module return a Hypergraph class (i.e. a simple, undirected
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hypergraph).
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"""
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from warnings import warn
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from easygraph.utils.exception import EasyGraphError
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__all__ = [
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"ring_lattice",
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]
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def ring_lattice(n, d, k, l):
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"""A ring lattice hypergraph.
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A d-uniform hypergraph on n nodes where each node is part of k edges and the
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overlap between consecutive edges is d-l.
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Parameters
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----------
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n : int
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Number of nodes
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d : int
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Edge size
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k : int
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Number of edges of which a node is a part. Should be a multiple of 2.
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l : int
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Overlap between edges
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Returns
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-------
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Hypergraph
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The generated hypergraph
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Raises
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------
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EasyGraphError
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If k is negative.
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Notes
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-----
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ring_lattice(n, 2, k, 0) is a ring lattice graph where each node has k//2 edges on
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either side.
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"""
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from easygraph.classes.hypergraph import Hypergraph
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if k < 0:
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raise EasyGraphError("Invalid k value!")
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if k < 2:
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warn("This creates a completely disconnected hypergraph!")
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if k % 2 != 0:
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warn("k is not divisible by 2")
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edges = [
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[node] + [(start + l + i) % n for i in range(d - 1)]
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for node in range(n)
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for start in range(node + 1, node + k // 2 + 1)
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]
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H = Hypergraph(num_v=n)
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H.add_hyperedges(edges)
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return H
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