chore: import upstream snapshot with attribution

swift/sequence_parallel/ring_utils.py

@@ -0,0 +1,58 @@
+# Some code borrowed from the awesome work: https://github.com/zhuzilin/ring-flash-attention
+# Copyright (c) ModelScope Contributors. All rights reserved.
+import torch
+import torch.distributed as dist
+from typing import Optional, Tuple
+
+
+class RingComm:
+
+    def __init__(self, process_group: dist.ProcessGroup):
+        self._process_group = process_group
+        self._ops = []
+        self.rank = dist.get_rank(self._process_group)
+        self.world_size = dist.get_world_size(self._process_group)
+        self._reqs = None
+
+        self.send_rank = (self.rank + 1) % self.world_size
+        self.recv_rank = (self.rank - 1) % self.world_size
+
+        if process_group is not None:
+            self.send_rank = dist.get_global_rank(self._process_group, self.send_rank)
+            self.recv_rank = dist.get_global_rank(self._process_group, self.recv_rank)
+
+    def send_recv(self, to_send: torch.Tensor, recv_tensor: Optional[torch.Tensor] = None) -> torch.Tensor:
+        if recv_tensor is None:
+            res = torch.empty_like(to_send)
+        else:
+            res = recv_tensor
+
+        send_op = dist.P2POp(dist.isend, to_send, self.send_rank, group=self._process_group)
+        recv_op = dist.P2POp(dist.irecv, res, self.recv_rank, group=self._process_group)
+        self._ops.append(send_op)
+        self._ops.append(recv_op)
+        return res
+
+    def commit(self):
+        if self._reqs is not None:
+            raise RuntimeError('commit called twice')
+        self._reqs = dist.batch_isend_irecv(self._ops)
+
+    def wait(self):
+        if self._reqs is None:
+            raise RuntimeError('wait called before commit')
+        for req in self._reqs:
+            req.wait()
+        self._reqs = None
+        self._ops = []
+
+    def send_recv_kv(
+        self,
+        k: torch.Tensor,
+        v: torch.Tensor,
+        k_buffer: Optional[torch.Tensor] = None,
+        v_buffer: Optional[torch.Tensor] = None,
+    ) -> Tuple[torch.Tensor, torch.Tensor]:
+        next_k, next_v = self.send_recv(k, k_buffer), self.send_recv(v, v_buffer)
+        self.commit()
+        return next_k, next_v