Jake Lishman

The Python `graphviz` package is not the actual Graphviz executable, which is what's required - the error message should hopefully explain this.

Not really, unfortunately - we don't use the Python wrapper from within Qiskit, and installing the wrapper doesn't install Graphviz, so it wouldn't really change the situation. If you've got...

The most immediate problem here is (I believe) in the drawers, not in `compose`. > Eg in the composed circuit, while the CircuitInstruction has updated qubits and clbits, the operation...

I said I'd come here from #12084 and comment, not realising I already had. To expand more, since my previous comment didn't go into enough detail: The `if_test` version is...

ASV highlighted an unexpected change in the benchmarks - the output from Sabre has changed somewhat from #11977, which wasn't intended to have affected the output in any way. I'll...

Ok, with #12172 cherry-picked on top of this branch, the same set of benchmarks that I ran in #12172 show RNG compatibility with `main` from before #11977 (and so with...

There seems to be a weird interaction with the default sort key of the `DAGInNode` and `DAGOutNode` instances, which are prefixed by a single letter (probably why your prefix thing...

No wait, `DAGInNode` and `DAGOutNode` override their `sort_key` to `"[]"`, nothing dependent on the wires. `"["` sorts lexicographically _after_ numbers but before lower-case letters in ASCII, so that seems to...

Ah ok, I think I've got it. Consider that the graphs contain `DAGInNode` and `DAGOutNode` instances, which have a non-zero sort key. When we start the topological sort, we first...

Sorry, I forgot to come back and answer the next day. The crux of the matter is that `topological_op_nodes` does _post_ selection from a complete topological order (including the in/out...