Qiskit / qiskit / 11702039606

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Commit Message

Add more default trials to sabre layout (#13360)

* Add more default trials to sabre layout

Right now sabre layout uses n random trials (as specified by the user or
defaulting to num_cpus) and since #12453 one additional trial taking the
qubits of the densest subgraph as a starting point. There are also a
couple of other trivial examples to try which may or may not produce
better results depending on the circuit, a trivial layout and a reverse
trivial layout. In the case of a hardware efficient circuit the trivial
layout will map exactly and would always be picked. When running in a
preset pass manager sabre should never be called in this scenario
because VF2Layout will find the mapping, but the incremental cost of
adding the trial is minimal. Similarly the cost of a reversed trivial
layout (where virtual qubit 0 -> n, 1 -> n - 1, etc.) is trivial and
may in some scenarios produce a better results.

* Update layouts for failing tests

* Add ring layouts for common connectivity graphs

* Add release notes and docs

* Apply suggestions from code review

Co-authored-by: Elena Peña Tapia <57907331+ElePT@users.noreply.github.com>

* Fix lint

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Co-authored-by: Elena Peña Tapia <57907331+ElePT@users.noreply.github.com>

Run Details

19 of 64 new or added lines in 1 file covered. (29.69%)

16 existing lines in 3 files now uncovered.

77066 of 86843 relevant lines covered (88.74%)

364673.8 hits per line