## Summary
- Replace the two-step `signal()` implementation (`incOutbound()` +
`atomicStore()`) with a single fire-and-forget PTX
`red.release.sys.global.add.u64` instruction
- This eliminates one local atomic fetch-add and replaces a remote store
with a remote atomic add that has no return value — more efficient on
both NVIDIA (PTX `red`) and AMD (compiler optimizes `(void)fetch_add` to
fire-and-forget `flat_atomic_add_x2`)
- Add a C++ perf test (`PERF_TEST`) in `mp_unit` for signal+wait
ping-pong latency
### Performance (H100, 2 ranks, signal+wait round-trip)
```
SemaphorePerfTest.SignalPingPong:
Store-based (old): 2.595 us/iter
Red-based (new): 2.345 us/iter
Speedup: 1.11x
```
## Test plan
- [x] Builds successfully (`make mp_unit_tests`)
- [x] `mpirun -np 2 ./build/bin/mp_unit_tests --filter
"SemaphorePerfTest"` — 1.11x speedup
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
The key purpose is handling all mscclpp objects' memory internally by
hiding shared pointers from user APIs.
* `Connection` class is now a wrapper of `BaseConnection` class that is
equivalent to the previous `Connection` class
* `connect()` methods now return `Connection` instead of
`std::shared_ptr<Connection>`
* Removed `connectOnSetup()` method
Provides two integration ways for MSCCL++ DSL.
1. Integrate with customized communication group
2. Integrate with NCCL API
Introduce new Python APIs to make it work:
```python
mscclpp.compile # compile dsl to json based execution plan
mscclpp.ExecutionPlanRegistry.register_plan(plan) # register the compiled plan to executionPlanRegistery
mscclpp.ExecutionPlanRegistry.set_selector(selector) # set the selector, the selector will return the best execution plan based on collection, message size, world size....
```
Fix#556
---------
Co-authored-by: Caio Rocha <caiorocha@microsoft.com>
Co-authored-by: Changho Hwang <changhohwang@microsoft.com>
