Qiskit / qiskit / 13000669575

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push

github

Committed by web-flow

Commit Message

Remove sort_key attribute from DAGNode (#13736)

* Remove sort_key attribute from DAGNode

Prior to having the DAGCircuit in rust the `sort_key` attribute was added
as a cache to speed up the lexicographical topological sort. Prior to
having this attribute the topological sort method would compute the sort
key as a string on the fly which ended up being a large bottleneck in
transpilation (see: #4040 for more details). However, since migrating
the DAGCircuit implementation to Rust this sort_key attribute isn't
needed anymore because we call the rustworkx-core function with a tuple
of bit objects instead of a string. The `sort_key` atribute was left on
in place for backwards compatibility (it shouldn't have been public,
this was a mistake in #4040) and when we create a python DAGNode object
that will be returned to Python the creation of the sort key is
unnecessary overhead (it takes roughly 1% of profile time to format the
sort_key string during transpilation). Since nothing in DAGCircuit is
actually using it this commit removes it to save the CPU cycles
creating the string on each dag creation. We will need to add a
deprecation to 1.4.0 to mark this removal for 2.0.0 since this was
missed in 1.3.0.

* Simplify star pre-routing sort_key logic

Run Details

32 of 32 new or added lines in 4 files covered. (100.0%)

3 existing lines in 2 files now uncovered.

79671 of 89589 relevant lines covered (88.93%)

351726.68 hits per line