Rust Integration: Full find_min_cut Rust Integration

[ohjuny]

This PR follows #1 (and replaces #2 ), which sets up pyo3 integration and replaces calls to nx.maximum_flow with a Rust implementation.

This PR replaces the entire call to find_min_cut with an equivalent Rust version. In particular, this means that the pre/post-processing of the capacity DAG is performed in Rust, and no Python/Rust context-switch is required during the entirety of find_min_cut.

Profiling across 9 workloads:

• Compared to original full-Python version:
  • Avg speedup: 3.61x
  • Max speedup: 4.98x
• Compared to Rust Integration: Perform Max Flow in Rust instead of Python #1 version:
  • Avg speedup: 1.52x
  • Max speedup: 1.77x

Additional notes: this PR initially aimed to also provide implementations for Operation and CostModel in Rust, so that annotate_capacity and reduce_durations could also be offloaded to Rust. However, there were some issues with using pyo3 to represent a trait-bound CostModel - there is a more detailed comment in the PR about this. The next steps for full Rust integration are outlined in Issue #4.

[ohjuny]

(just noting down some things for myself)

Cost Model Issues
CostModel in Python is abstract base class - in Rust this is a trait. Operations have a cost model, which is generic over this trait. But pyo3 doesn't support passing in trait-bound objects. There are workarounds, in particular using Box<dyn ModelCost> where ModelCost is the trait - CostModel contains a dyn Box to ExponentialModel. But this makes the CostModel constructor weird, in that it needs to take in a dynamic type, which pyo3 doesn't support.

• Summary Doc: https://docs.google.com/document/d/1HwbvBKhANBGl3dqMQBkt3siUz9hYkipNH9atkt5IooA/
• Generic Classes: Question: How can I pass generic cutom classes to a method PyO3/pyo3#696
• Boxed Input: [Python] Support recursive shapes that are boxed in Rust smithy-lang/smithy-rs#2476
• Box in new: https://stackoverflow.com/questions/75159336/using-box-with-pyo3
• pyo3 trait bound function: https://pyo3.rs/main/trait-bounds
• Trait-bound input: https://stackoverflow.com/questions/77707102/how-to-use-a-trait-as-parameter-of-pymethod-in-pyo3

Edit: also found this dedicated trait bounds guide on the official pyo3 docs, didn't look through it deeply but could be helpful.

[ohjuny]

The maturin-generated CI test for macos-12, x86_64 fails for some reason (wasn't failing in #1 ) so I commented it out in e489444. The only config I changed since #1 is that I updated pyo3 from 0.22.0 to 0.23.3 (because some other test was failing due to out-of-date pyo3). I think this should be fine but thought I'd leave a note.

[jaywonchung]

Beautiful. Nothing major. Thanks for your work!

[jaywonchung]

LGTM, very cool. Thanks @ohjuny!

[jaywonchung]

Just realized some commits mentioned in #2 might be in branches? @ohjuny Please clean up only the branches that can be deleted.

[ohjuny]

Just realized some commits mentioned in #2 might be in branches? @ohjuny Please clean up only the branches that can be deleted.

Do you mean #4 ? If so, I think I can just keep this lowtime-rust-full-rust branch and delete the lowtime-rust-each-iter branch from #1 .

[jaywonchung]

Oh, you're right. Sounds good!