Qiskit / qiskit / 25445566101

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github

Committed by web-flow

Commit Message

Add a rust iterator implementation for a dag's nodes_on_wire (#15999)

* Add a rust iterator implementation for a dag's nodes_on_wire

The nodes_on_wire DAGCircuit rust method was needlessly allocating the
result into an intermediate vector. This was mostly an artifact of the
python interface which was needs to return a list to produce an iterator
(assuming the api doesn't actually return a list). But, in a rust context
we don't want to eagerly create a vector. The only current rust space
consumer is a pass that is just iterating over the nodes and the vector
is just adding extra overhead. This commit adds a new iterator method
that does the iteration over the nodes without any allocation. The
current method is left in place because it is used by the python
interface and also it doesn't panic if given an invalid wire and has an
option to only include op nodes. While this new method just returns the
iterator or panics.

This also updates the sole use of the DAGCircuit::nodes_on_wire() method
from rust since this method is being added for rust consumers to avoid
an unnecessary allocation.

* Replace the rust inner method with new iterator

This commit replaces the previously left intact rust method that built
an inner vec and replaces it with the new iterator returning method.
There wasn't really a need to keep the old method around as what was
really needed was just to preserve the python interface which was
trivial to do using the iterator in the python interface methods.

* Simplify iterator implementation

* Update size hint to be valid at all points in iteration

This commit updates the iterator's size_hint implementation to correctly
provide a hint at all points in iteration. Previously this incorrectly
only returned a hint for the start of the iterator.

Co-authored-by: Jake Lishman <jake.lishman@ibm.com>

---------

Co-authored-by: Jake Lishman <jake.lishman@ibm.com>

Coverage Stats

30 of 34 new or added lines in 2 files covered. (88.24%)

10 existing lines in 3 files now uncovered.

106947 of 122056 relevant lines covered (87.62%)

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