Qiskit / qiskit / 11803930745

Pull #13425

github

Avoid overhead for synthesized nodes lookup (#13424)

After #12550 a hash implementation was added to the implementation
of DAGOpNode to be able to have identical instances of dag nodes used be
usable in a set or dict. This is because after #12550 changed the
DAGCircuit so the DAGOpNode instances were just a python view of the
data contained in the nodes of a dag. While prior to #12550 the actual
DAGOpNode objects were returned by reference from DAG methods. However,
this hash implementation has additional overhead compared to the object
identity based version used before. This has caused a regression in some
cases for high level synthesis when it's checking for nodes it's already
synthesized. This commit addresses this by changing the dict key to be
the node id instead of the node object. The integer hashing is
significantly faster than the object hashing.

(cherry picked from commit 8c6ad024c)

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