Qiskit / qiskit / 10686234237

88%

Build Type

push

github

Committed by web-flow

Commit Message

Avoid `ExtraInstructionAttributes` allocation on `unit="dt"` (#13078)

The default value for `Instruction.unit` is `"dt"`.  Previously, the
`OperationFromPython` extraction logic would only suppress allocation of
the extra instruction attributes if all the contained fields were
`None`, but `None` is not actually a valid value of `Instruction.unit`
(which must be a string).  This meant that `OperationFromPython` would
always allocate and store extra attributes, even for the default cases.
This did not affect standard gates appended using their corresponding
`QuantumCircuit` methods (since no Python-space extraction is
performed in that case), but did affect standard calls to `append`, or
anything else that entered from Python space.

This drastically reduces the memory usage of circuits built by
`append`-like methods. Ignoring the inefficiency factor of the
heap-allocation implementation, this saves 66 bytes plus
small-allocation overhead for 2-byte heap allocations (another 14 bytes
on macOS, but will vary depending on the allocator) per standard
instruction, which is on the order of 40% memory-usage reduction.

Run Details

17 of 26 new or added lines in 2 files covered. (65.38%)

6 existing lines in 3 files now uncovered.

72447 of 81260 relevant lines covered (89.15%)

406282.77 hits per line