Qiskit / qiskit / 26254975289

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github

Committed by web-flow

Commit Message

Use `ParameterVector(uuid=...)` in QPY deserialisation (#16221)

When QPY deserialises `ParameterVectorElement`s, it first created a
dummy `ParameterVectorElement` with a random UUID, then mutated an
internal Python-space cache of the elements individually, as they were
encountered, to reset them to the `root_uuid + offset` form.

The idea that we _can_ find the root vector during deserialisation is
predicated on the assumption that the `root_uuid + offset` form _must_
hold; if it doesn't, then the attempt to look up a cached version of the
vector by looking at the `element_uuid - offset` would fail, so we'd
never return the same vector.

When `ParameterVectorElement` serialisation was introduced in QPY
v3[^1], vectors were still being looked up by name, and the elements had
completely disconnected UUIDs, which motivated the original system.
This is no longer the case on both counts; it is now much easier simply
to generate the vector correctly from the start, and never need to
mutate internal private state.

[^1]: 5c4cd2bbcf: Fix ParameterVector handling in QPY serialization (gh-7381)

Coverage Stats

12 of 12 new or added lines in 2 files covered. (100.0%)

22 existing lines in 4 files now uncovered.

108380 of 123872 relevant lines covered (87.49%)

955912.35 hits per line