Qiskit / qiskit / 10147014904

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github

Committed by web-flow

Commit Message

 Port `star_preroute` to rust (#12761)

* This commit ports the core logic of `star_preroute` from Python to Rust. The changes involve creating a new Rust module for the star prerouting algorithm and updating the corresponding Python code to integrate with this new Rust functionality.

Details:
- New Rust file: Added `star_preroute.rs` to handle the core logic of the function `star_preroute` from the python side. This file defines the type aliases for node and block representations, which matches the current block representation of the `StarBlock` (except that the center is just a bool, as we only need to know if there is a center), and the node representation matches how the nodes used in `SabreDAG`. The `star_preroute` function processes the star blocks witihin the `SabreDAG`  and finds the linear routing equivalent and then returns the result as a `SabreResult`. Thus we can use the same methods we used in Sabre, such as `_build_sabre_dag` and `_apply_sabre_result`.
- Node representation: A key part of this implementation is how it takes advantage of `SabreResult` and `SabreDAG`, so the node representation is a tuple of the node id, list of qubit indices, a set of classical bit indices, and a directive flag. However, once we update the regular DAG to rust, this part may change significantly.
- Updates in the SABRE rust module: To use `sabre_dag.rs` and `swap_map.rs` in `star_prerouting`, I change them to be public in `crates/accelerate/src/sabre/mod.rs`. Not sure if it makes more sense to do it this way or to move `star_prerouting` to `crates/accelerate/src/sabre/` since it mimics the methods used in Sabre to change the dag.
- Python side updates: Imported the necessary modules and only modified the function `star_preroute` so that now the function performs the heavy lifting of transforming the DAG within the Rust space, leveraging `_build_sabre_dag` and `_apply_sabre_result`.
- Possible issues: I was not sure how correctly handle control flow from ... (continued)

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