Commits on Feb 17, 2023

1. Improve efficiency of CouplingMap.make_symmetric (#9571) …

   * Improve efficiency of CouplingMap.make_symmetric
   
   Right now the CouplingMap.make_symmetric has a quadratic overhead. It
   was iterating over a list of each edgess' endpoints in the graph
   and for each edge it was iterating over the same list again to check
   whether the reverse edge is present or not. The overhead for this for
   large coupling maps can be quite large, for example with a 10497 qubit
   heavy hex coupling map the time it took to run this method as part of
   SabreLayout's initialization was 10x slower than actually running the
   pass (a equally sized Bernstein-Vazirani circuit). Instead of doing an
   O(n) contains check inside the loop this commit updates it to use a
   set which will be an O(1) lookup. This should address the performance
   issue with this method. In the future we should leverage the native
   rustworkx method to do this, which is being added in:
   Qiskit/rustworkx#814
   
   * Further reduce the overhead by avoiding CouplingMap.add_edge()
   
   The CouplingMap add_edge() method has similar overhead to check whether
   nodes need to be added. However, in the case of make_symmetric we don't
   need this checking because both endpoints are already in the graph. This
   commit further improves the performance of the method by just adding the
   reverse edge directly to the graph via the rustworkx api instead.
   
   (cherry picked from commit 5afbb0b)

   

   mtreinish authored and mergify[bot] committed Feb 17, 2023
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