Need method for extracting a initial Layout without running PassManager

[nonhermitian]

What is the expected behavior?

I would like to see what the Layout from virtual to physical qubits is without having to construct and run a PassManager. i.e. I want to be able to easily plot something like this:

[ajavadia]

Even with a PassManager this is a bit unreliable right now, need to resolve #2066 and #1831 first and make all mappers consistent in how they use Layout.

During the transpilation process a few things can happen that can make the above visualization hard to achieve:

• ancilla allocation: extra qubits may be used as scratch space for swaps
• final layout vs. initial layout: the final layout of qubits may be permuted (in fact it usually is)

[nonhermitian]

Yes, I should have been a bit more specific in my title. I would like to extract the initial layout that is chosen without actually doing a full transpile. i.e. I want to see the difference in qubit selection between DenseLayout and NoiseAdapativeLayout without transpiling both.

[1ucian0]

After #2736, the layout is saved as circuit.layout after transpilation. Is this solving this issue?

[nonhermitian]

yep

[1ucian0]

Reopening, because #2736 was kinda reverted by #2928

[1ucian0]

Is this a 0.9 issue @ajavadia ?

[nonhermitian]

This can be closed.