Improve SabreSwap error message on unexpanded circuits #9909
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`SabreSwap` requires that the input circuit is exactly the same size as the system implied by the coupling map, since this is used internally in Rust for the virtual-to-physical mapping. Failure to ensure this can lead to panics in the Rust code. This commit catches the failure case (for free) in Python space, and attempts to help the user work out what they needed.
jakelishman
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LGTM, this is straightforward enough. I was going to ask that we wait until after #9840 to ensure the conditions match in the case of disjoint coupling map. But I don't think it'll be an issue because layout should work and also at least in the preset pass managers we don't ever run this pass in practice. It does remind me that for #9840 after I rebase it I should probably add a release note for layout pass authors about the disconnected coupling maps and how to handle them.
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I'd actually forgotten that we had #9840 on the go when I wrote this. Yeah, for sure we can revisit the error messages as part of that too. |
`SabreSwap` requires that the input circuit is exactly the same size as the system implied by the coupling map, since this is used internally in Rust for the virtual-to-physical mapping. Failure to ensure this can lead to panics in the Rust code. This commit catches the failure case (for free) in Python space, and attempts to help the user work out what they needed.
`SabreSwap` requires that the input circuit is exactly the same size as the system implied by the coupling map, since this is used internally in Rust for the virtual-to-physical mapping. Failure to ensure this can lead to panics in the Rust code. This commit catches the failure case (for free) in Python space, and attempts to help the user work out what they needed.
Summary
SabreSwaprequires that the input circuit is exactly the same size as the system implied by the coupling map, since this is used internally in Rust for the virtual-to-physical mapping. Failure to ensure this can lead to panics in the Rust code. This commit catches the failure case (for free) in Python space, and attempts to help the user work out what they needed.Details and comments
This was prompted by a discussion in Slack about the confusing error, though I've done approximately the same thing myself before and got confused.