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Identifier
Values
=>
Cc0020;cc-rep
([],1)=>0 ([],2)=>0 ([(0,1)],2)=>1 ([],3)=>0 ([(1,2)],3)=>1 ([(0,2),(1,2)],3)=>1 ([(0,1),(0,2),(1,2)],3)=>2 ([],4)=>0 ([(2,3)],4)=>1 ([(1,3),(2,3)],4)=>1 ([(0,3),(1,3),(2,3)],4)=>1 ([(0,3),(1,2)],4)=>2 ([(0,3),(1,2),(2,3)],4)=>2 ([(1,2),(1,3),(2,3)],4)=>2 ([(0,3),(1,2),(1,3),(2,3)],4)=>2 ([(0,2),(0,3),(1,2),(1,3)],4)=>1 ([(0,2),(0,3),(1,2),(1,3),(2,3)],4)=>2 ([(0,1),(0,2),(0,3),(1,2),(1,3),(2,3)],4)=>3 ([],5)=>0 ([(3,4)],5)=>1 ([(2,4),(3,4)],5)=>1 ([(1,4),(2,4),(3,4)],5)=>1 ([(0,4),(1,4),(2,4),(3,4)],5)=>1 ([(1,4),(2,3)],5)=>2 ([(1,4),(2,3),(3,4)],5)=>2 ([(0,1),(2,4),(3,4)],5)=>2 ([(2,3),(2,4),(3,4)],5)=>2 ([(0,4),(1,4),(2,3),(3,4)],5)=>2 ([(1,4),(2,3),(2,4),(3,4)],5)=>2 ([(0,4),(1,4),(2,3),(2,4),(3,4)],5)=>2 ([(1,3),(1,4),(2,3),(2,4)],5)=>1 ([(0,4),(1,2),(1,3),(2,4),(3,4)],5)=>2 ([(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>2 ([(0,4),(1,3),(2,3),(2,4),(3,4)],5)=>2 ([(0,4),(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>2 ([(0,3),(0,4),(1,3),(1,4),(2,3),(2,4)],5)=>1 ([(0,3),(0,4),(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>2 ([(0,4),(1,3),(2,3),(2,4)],5)=>2 ([(0,1),(2,3),(2,4),(3,4)],5)=>3 ([(0,3),(1,2),(1,4),(2,4),(3,4)],5)=>3 ([(0,3),(0,4),(1,2),(1,4),(2,4),(3,4)],5)=>3 ([(0,3),(0,4),(1,2),(1,4),(2,3)],5)=>3 ([(0,1),(0,4),(1,3),(2,3),(2,4),(3,4)],5)=>2 ([(0,3),(0,4),(1,2),(1,4),(2,3),(2,4),(3,4)],5)=>3 ([(0,4),(1,2),(1,3),(2,3),(2,4),(3,4)],5)=>3 ([(1,2),(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>3 ([(0,4),(1,2),(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>3 ([(0,3),(0,4),(1,2),(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>3 ([(0,3),(0,4),(1,2),(1,3),(1,4),(2,3),(2,4)],5)=>2 ([(0,2),(0,3),(0,4),(1,2),(1,3),(1,4),(2,4),(3,4)],5)=>2 ([(0,2),(0,3),(0,4),(1,2),(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>3 ([(0,1),(0,2),(0,3),(0,4),(1,2),(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>4 ([],6)=>0 ([(4,5)],6)=>1 ([(3,5),(4,5)],6)=>1 ([(2,5),(3,5),(4,5)],6)=>1 ([(1,5),(2,5),(3,5),(4,5)],6)=>1 ([(0,5),(1,5),(2,5),(3,5),(4,5)],6)=>1 ([(2,5),(3,4)],6)=>2 ([(2,5),(3,4),(4,5)],6)=>2 ([(1,2),(3,5),(4,5)],6)=>2 ([(3,4),(3,5),(4,5)],6)=>2 ([(1,5),(2,5),(3,4),(4,5)],6)=>2 ([(0,1),(2,5),(3,5),(4,5)],6)=>2 ([(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,5),(1,5),(2,5),(3,4),(4,5)],6)=>2 ([(1,5),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,5),(1,5),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(2,4),(2,5),(3,4),(3,5)],6)=>1 ([(0,5),(1,5),(2,4),(3,4)],6)=>2 ([(1,5),(2,3),(2,4),(3,5),(4,5)],6)=>2 ([(0,5),(1,5),(2,3),(3,4),(4,5)],6)=>2 ([(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(1,5),(2,4),(3,4),(3,5),(4,5)],6)=>2 ([(0,5),(1,5),(2,4),(3,4),(4,5)],6)=>2 ([(0,5),(1,5),(2,3),(2,4),(3,5),(4,5)],6)=>2 ([(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,5),(1,5),(2,4),(3,4),(3,5),(4,5)],6)=>2 ([(0,5),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(1,4),(1,5),(2,4),(2,5),(3,4),(3,5)],6)=>1 ([(0,5),(1,4),(2,4),(2,5),(3,4),(3,5)],6)=>2 ([(0,5),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5)],6)=>2 ([(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,5),(1,4),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,5),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,4),(0,5),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5)],6)=>1 ([(0,4),(0,5),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,5),(1,4),(2,3)],6)=>3 ([(1,5),(2,4),(3,4),(3,5)],6)=>2 ([(0,1),(2,5),(3,4),(4,5)],6)=>3 ([(1,2),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,4),(2,3),(3,5),(4,5)],6)=>3 ([(1,4),(2,3),(2,5),(3,5),(4,5)],6)=>3 ([(0,1),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,4),(1,5),(2,3),(2,5),(3,5),(4,5)],6)=>3 ([(1,4),(1,5),(2,3),(2,5),(3,5),(4,5)],6)=>3 ([(0,5),(1,4),(1,5),(2,3),(2,5),(3,5),(4,5)],6)=>3 ([(1,4),(1,5),(2,3),(2,5),(3,4)],6)=>3 ([(0,5),(1,4),(2,3),(2,4),(3,5),(4,5)],6)=>3 ([(1,2),(1,5),(2,4),(3,4),(3,5),(4,5)],6)=>2 ([(0,5),(1,2),(1,4),(2,3),(3,5),(4,5)],6)=>3 ([(1,5),(2,3),(2,4),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,4),(2,3),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,2),(1,5),(2,4),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(1,4),(1,5),(2,3),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,4),(1,5),(2,3),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,4),(2,3),(2,4),(3,5)],6)=>3 ([(0,1),(2,4),(2,5),(3,4),(3,5)],6)=>2 ([(0,5),(1,5),(2,3),(2,4),(3,4)],6)=>3 ([(0,4),(1,2),(1,3),(2,5),(3,5),(4,5)],6)=>2 ([(0,4),(1,2),(1,5),(2,5),(3,4),(3,5)],6)=>3 ([(0,4),(1,2),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,1),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,4),(1,4),(2,3),(2,5),(3,5),(4,5)],6)=>3 ([(0,3),(0,4),(1,2),(1,5),(2,5),(3,5),(4,5)],6)=>3 ([(0,3),(1,4),(1,5),(2,4),(2,5),(3,5),(4,5)],6)=>3 ([(0,4),(1,2),(1,5),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,1),(0,5),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,5),(2,3),(2,4),(3,4),(3,5),(4,5)],6)=>3 ([(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,1),(0,5),(1,4),(2,4),(2,5),(3,4),(3,5)],6)=>3 ([(0,3),(0,5),(1,3),(1,5),(2,4),(2,5),(3,4),(4,5)],6)=>2 ([(0,3),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,4),(1,5),(2,3),(2,4),(3,4),(3,5),(4,5)],6)=>3 ([(0,1),(0,5),(1,4),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,4),(0,5),(1,4),(1,5),(2,3),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5)],6)=>3 ([(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,4),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,4),(0,5),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5)],6)=>2 ([(0,4),(0,5),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,3),(1,4),(2,3),(2,4),(3,5),(4,5)],6)=>2 ([(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5)],6)=>2 ([(0,5),(1,3),(1,4),(2,3),(2,4),(2,5),(3,5),(4,5)],6)=>2 ([(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,5),(4,5)],6)=>2 ([(0,5),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,5),(4,5)],6)=>2 ([(0,4),(0,5),(1,2),(1,3),(2,5),(3,4)],6)=>3 ([(0,5),(1,2),(1,4),(2,3),(3,4),(3,5),(4,5)],6)=>2 ([(0,1),(0,2),(1,5),(2,4),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,4),(2,3),(2,4),(2,5),(3,4),(3,5)],6)=>3 ([(0,5),(1,3),(1,4),(2,4),(2,5),(3,4),(3,5)],6)=>3 ([(0,4),(1,3),(1,5),(2,3),(2,4),(2,5),(3,5),(4,5)],6)=>3 ([(0,5),(1,2),(1,3),(1,4),(2,3),(2,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,2),(1,3),(1,4),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,3),(1,4),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,4),(0,5),(1,2),(1,3),(2,3),(4,5)],6)=>4 ([(0,2),(1,4),(1,5),(2,3),(3,4),(3,5),(4,5)],6)=>3 ([(0,1),(0,5),(1,5),(2,3),(2,4),(3,4),(4,5)],6)=>4 ([(0,1),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>4 ([(0,1),(0,5),(1,5),(2,3),(2,4),(3,4),(3,5),(4,5)],6)=>4 ([(0,1),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>4 ([(0,1),(0,5),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>4 ([(0,4),(0,5),(1,2),(1,3),(1,4),(2,3),(2,5),(3,5),(4,5)],6)=>3 ([(0,3),(1,2),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>4 ([(0,1),(0,5),(1,4),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,3),(0,5),(1,2),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>4 ([(0,1),(0,5),(1,4),(2,3),(2,4),(2,5),(3,4),(3,5)],6)=>4 ([(0,3),(0,4),(1,2),(1,4),(1,5),(2,3),(2,5),(3,5),(4,5)],6)=>3 ([(0,3),(0,4),(0,5),(1,2),(1,4),(1,5),(2,3),(2,5),(3,5),(4,5)],6)=>4 ([(0,4),(0,5),(1,2),(1,3),(1,5),(2,3),(2,4),(3,4),(3,5),(4,5)],6)=>3 ([(0,2),(0,5),(1,3),(1,4),(1,5),(2,3),(2,4),(3,4),(3,5),(4,5)],6)=>3 ([(0,4),(0,5),(1,2),(1,3),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>4 ([(0,5),(1,2),(1,3),(1,4),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>4 ([(1,2),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>4 ([(0,5),(1,2),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>4 ([(0,4),(0,5),(1,2),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>4 ([(0,4),(0,5),(1,2),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5)],6)=>3
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Description
The biclique partition number of a graph.
The biclique partition number of a graph is the minimum number of pairwise edge disjoint complete bipartite subgraphs so that each edge belongs to exactly one of them. A theorem of Graham and Pollak [1] asserts that the complete graph $K_n$ has biclique partition number $n - 1$.
References
[1] Graham, R. L., Pollak, H. O. On the addressing problem for loop switching MathSciNet:0289210
Code
@cached_function
def statistic(G, certificate=False, verbose=False):
    """
    sage: [statistic(graphs.CompleteGraph(n)) for n in range(1,6)]
    [0, 1, 2, 3, 4]
    sage: [statistic(graphs.PathGraph(n)) for n in range(1,8)]
    [0, 1, 1, 2, 2, 3, 3]
    sage: [statistic(graphs.CycleGraph(n)) for n in range(1,8)]
    [0, 1, 2, 1, 3, 3, 4]
    sage: n=5; all(statistic(G) <= n-G.independent_set(value_only=True) for G in graphs(n))
    True
    """
    E = G.edges(labels=False)
    if not E:
        return 0
    for c in range(1, len(E)+1):
        for p in SetPartitions(E, c):
            if verbose: print("P", p)
            for b in p:
                V = [u for e in b for u in e]
                H = G.subgraph(edges=b, vertices=V)
                if verbose: print("V", H.vertices(), "E", H.edges(labels=False))
                is_bipartite, bipartition = H.is_bipartite(certificate=True)
                if is_bipartite:
                    if verbose: print(bipartition)
                    k = list(bipartition.values()).count(0)
                    l = H.num_verts() - k
                    B = graphs.CompleteBipartiteGraph(k, l)
                    if not H.is_isomorphic(B):
                        if verbose: print("not complete")
                        break
                else:
                    if verbose: print("not bipartite")                    
                    break
            else:
                if certificate:
                    return c, p
                return c
                
Created
Jun 28, 2022 at 12:09 by Martin Rubey
Updated
Aug 04, 2024 at 22:07 by Martin Rubey