chore: import upstream snapshot with attribution

python/ray/util/collective/examples/nccl_allreduce_example.py

@@ -0,0 +1,37 @@
+import cupy as cp
+
+import ray
+import ray.util.collective as collective
+
+
+@ray.remote(num_gpus=1)
+class Worker:
+    def __init__(self):
+        self.send = cp.ones((4,), dtype=cp.float32)
+        self.recv = cp.zeros((4,), dtype=cp.float32)
+
+    def setup(self, world_size, rank):
+        collective.init_collective_group(world_size, rank, "nccl", "default")
+        return True
+
+    def compute(self):
+        collective.allreduce(self.send, "default")
+        return self.send
+
+    def destroy(self):
+        collective.destroy_group()
+
+
+if __name__ == "__main__":
+    send = cp.ones((4,), dtype=cp.float32)
+    ray.init(num_gpus=2)
+    num_workers = 2
+    workers = []
+    init_rets = []
+    for i in range(num_workers):
+        w = Worker.remote()
+        workers.append(w)
+        init_rets.append(w.setup.remote(num_workers, i))
+    _ = ray.get(init_rets)
+    results = ray.get([w.compute.remote() for w in workers])
+    ray.shutdown()