support stage2 for gradient merge. (#47711)

python/paddle/distributed/fleet/meta_parallel/sharding/group_sharded_stage2.py

@@ -418,17 +418,6 @@ class GroupShardedStage2(nn.Layer):
                         )
                     )
 
-                    if self._dp_group and self._dp_group.nranks > 1:
-                        assert (
-                            not self._reduce_overlap
-                        ), 'dp + stage2 hybrid parallel only Synchronize due to the new communication lib.'
-                        # TODO(wuhuachao):after the new communication lib upgrading, overlapping the comm of dp + stage2.
-                        dist.all_reduce(
-                            tensor=param.grad,
-                            group=self._dp_group,
-                            sync_op=True,
-                        )
-
                     # Clear the task flow and trigger callback to clear the redundant gradient
                     # self._clear_task_flow()
 
@@ -485,17 +474,6 @@ class GroupShardedStage2(nn.Layer):
                             )
                         )
 
-                        if self._dp_group and self._dp_group.nranks > 1:
-                            assert (
-                                not self._reduce_overlap
-                            ), 'dp + stage2 hybrid parallel only Synchronize due to the new communication lib.'
-                            # TODO(wuhuachao):after the new communication lib upgrading, overlapping the comm of dp + stage2.
-                            dist.all_reduce(
-                                tensor=grad_storage.buffer,
-                                group=self._dp_group,
-                                sync_op=True,
-                            )
-
                         cleanup()
 
                     # Clear the task flow and trigger callback to clear the redundant gradient
@@ -648,8 +626,34 @@ class GroupShardedStage2(nn.Layer):
             )
         return rank_buffer_size
 
+    def _dp_allreduce(self):
+        # do dp allreduce here for gradient merge.
+        if self._dp_group and self._dp_group.nranks > 1:
+            for dtype in self._grad_storages.keys():
+                for rank, g in sorted(
+                    self._grad_storages[dtype].items(), key=lambda x: x[0]
+                ):
+                    if g.destination == self._rank:
+                        assert g.buffer._is_initialized()
+                        dist.all_reduce(
+                            tensor=g.buffer,
+                            group=self._dp_group,
+                            sync_op=True,
+                        )
+            for param in self._trainable_params:
+                if param.name in self._param_grads and param.grad is not None:
+                    dst_rank = self._trainable_param2rank[param.name]
+                    if dst_rank == self._rank:
+                        dist.all_reduce(
+                            tensor=param.grad,
+                            group=self._dp_group,
+                            sync_op=True,
+                        )
+
     def _redefine_opt_step(self):
         grad_func = self._grad_scale
+        dp_allreduce_func = self._dp_allreduce
+
         for opt in self._sharding_optimizers:
             opt_step = opt.step
 
@@ -658,7 +662,9 @@ class GroupShardedStage2(nn.Layer):
                     # Wait for the last reduce task. This wait must before grad scale function.
                     assert self._comm_task is not None
                     self._comm_task.wait()
+
                 grad_func()
+                dp_allreduce_func()
                 opt_step()
 
             opt.step = MethodType(_opt_step, opt)

python/paddle/distributed/fleet/meta_parallel/sharding/group_sharded_utils.py

@@ -23,7 +23,6 @@ from paddle.fluid import core
 from paddle.fluid import layers
 from paddle.fluid.dygraph import to_variable
 from paddle.fluid.framework import dygraph_only
-from paddle.distributed import fleet, ParallelMode
 
 
 class Taskflow:
@@ -245,18 +244,8 @@ def GroupShardedScaler(scaler):
         self._found_inf = 1 if temp_found_inf_fp16 or temp_found_inf_fp32 else 0
         is_found_inf = paddle.to_tensor([self._found_inf], dtype="int32")
 
-        hcg = fleet.fleet._hcg if hasattr(fleet.fleet, "_hcg") else None
-        hybrid_parallel = (
-            hcg is not None
-            and hcg.get_parallel_mode() is not ParallelMode.DATA_PARALLEL
-        )
-
         paddle.distributed.all_reduce(
-            is_found_inf,
-            op=paddle.distributed.ReduceOp.MAX,
-            group=hcg.get_check_parallel_group()
-            if hybrid_parallel
-            else optimizer._group,
+            is_found_inf, op=paddle.distributed.ReduceOp.MAX, group=None
         )
         self._found_inf = is_found_inf.numpy()[0]
 

python/paddle/fluid/tests/unittests/collective/fleet/dygraph_group_sharded_api_eager.py

@@ -148,11 +148,6 @@ def test_sharding_api():
 
     output_dir = tempfile.mkdtemp()
 
-    # test sharding + dp, just for test
-    dp_group = paddle.distributed.new_group(
-        list(range(paddle.distributed.get_world_size()))
-    )
-
     # fp16
     stage2_params = train_mlp(
         mlp1,