dwave_networkx.algorithms.elimination_ordering.pegasus_elimination_order#

pegasus_elimination_order(n, coordinates=False)[source]#

Provides a variable elimination order for the Pegasus graph.

The treewidth of a Pegasus graph pegasus_graph(n) is lower-bounded by \(12n-11\) and upper bounded by \(12n-4\) [BBRR] .

Simple pegasus variable elimination order rules:

  • eliminate vertical qubits, one column at a time

  • eliminate horizontal qubits in each column once their adjacent vertical qubits have been eliminated

Parameters:

  • n (int) – The size parameter for the Pegasus lattice.

  • coordinates (bool, optional (default False)) – If True, the elimination order is given in terms of 4-term Pegasus coordinates, otherwise given in linear indices.

Returns:

order – An elimination order that provides an upper bound on the treewidth.

Return type:

list