Qiskit / qiskit / 17940378364

88%

Build Type

push

github

Committed by web-flow

Commit Message

Fix edge-order non-determinism when adding DAG nodes (#15040)

All of `DAGCircuit::push_back`, `DAGCircuit::push_front` and
`DAGCircuitBuilder::push_back` had non-determinisms in the precise order
that edges were added.  The two `DAGCircuit` methods had diverged, so
exhibited _different_ behaviour.  Most of the effects were limited to
nodes with multiple classical in edges, though `DAGCircuit::push_back`
did have some problems with high-degree quantum nodes (like barriers) as
well.

This commit unifies the code handled the two `DAGCircuit` methods to try
and prevent divergences (especially since `apply_operation_front` is
currently little used and little tested).  As a side effect, this fixed
a bug in `apply_operation_front` around handling multiple references to
the same clbit or var in classical expressions that was fixed in
`apply_operation_back` some time prior.

Run Details

34 of 34 new or added lines in 1 file covered. (100.0%)

12 existing lines in 4 files now uncovered.

92722 of 105017 relevant lines covered (88.29%)

934765.26 hits per line