Qiskit / qiskit / 16988585462

88%

Build Type

push

github

Committed by web-flow

Commit Message

Fix non-determinism in `CommutativeCancellation` (#14763)

The use of `HashMap` and `HashSet` for internal tracking structures in
the pass, which were subsequently iterated over, caused node removals
to happen in a non-deterministic order, which in turn could cause the
edge structure of the `DAGCircuit` to be non-deterministic.  This did
not affect a topological iteration over the nodes when canonicalised by
the `qargs` and `cargs`, but passes (such as Rust-space Sabre) that
iterate over the edge structure themselves can observe the
non-determinism.

Sabre wants to iterate over the edges itself because, as a routing
algorithm, it is implementing its own coroutine variant of topological
ordering on a related graph.

Run Details

6 of 6 new or added lines in 3 files covered. (100.0%)

10 existing lines in 3 files now uncovered.

87899 of 99568 relevant lines covered (88.28%)

510112.62 hits per line