Adjust graphviz options for better layout with plot_gate_map()

[mtreinish]

Summary

This commit fixes an issue with the visualizations of some backends/coupling maps. The default neato settings worked well in most cases but for some graphs it was not generating a good layout. This tweaks the settings a bit so that layouts work with more classes of graphs.

Details and comments

[qiskit-bot]

One or more of the following people are relevant to this code:

• @enavarro51
• @Qiskit/terra-core

[1ucian0]

ibm_fez

[mtreinish]

Based on that image I'm wondering if we want to scale up the fontsize a bit?

[coveralls]

Pull Request Test Coverage Report for Build 10705646259

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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Details

• 0 of 15 (0.0%) changed or added relevant lines in 1 file are covered.
• 22 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.03%) to 89.16%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit/visualization/gate_map.py	0	15	0.0%

Files with Coverage Reduction	New Missed Lines	%
qiskit/visualization/gate_map.py	1	6.69%
qiskit/transpiler/passes/synthesis/unitary_synthesis.py	2	88.43%
qiskit/synthesis/two_qubit/xx_decompose/decomposer.py	7	90.84%
crates/qasm2/src/parse.rs	12	97.15%

Totals
Change from base Build 10691830429:	-0.03%
Covered Lines:	72526
Relevant Lines:	81344

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💛 - Coveralls

[1ucian0]

ibm_quebec

[mtreinish]

That second example looks like we should condition:

https://github.com/Qiskit/qiskit/pull/12770/files#diff-ff70fb816cde3f453d870891f47ede8245855a9e156228201a53fd613ad00659R1096-R1100

on if not qubit_coordinates and only use these graph attributes if we're doing an algorithmic layout.

[1ucian0]

In the last change, I changed to prism and I got the following results:

ibm_fez

ibm_cusconazca

ibm_torino

ibm_kyiv

If you are happy when them, I will update the image references and merge.

[mtreinish]

If you are happy when them, I will update the image references and merge.

Those look fine to me, the ibm_torino one is maybe a bit less pretty than ibm_fez and ibm_cusconazca but it looks fine. So let's just go with this.

[ElePT]

It looks like the font size still needs some tweaking:

[1ucian0]

[Cryoris]

Thanks for the final tweaks @1ucian0 !