[Cherry-pcik]add release for color sharding (#68826)

python/paddle/distributed/fleet/meta_optimizers/dygraph_optimizer/dygraph_sharding_optimizer.py

@@ -810,7 +810,8 @@ def clear_grad_func(p):
 
         if self.sd_release_grads and not self.pp_overlap:
             for comm_buffer in self._comm_buffer_list:
-                comm_buffer._clear_grad_storage()
+                if comm_buffer.need_reduce_scale_sync():
+                    comm_buffer._clear_grad_storage()
 
     def filter_parameters(self, parameter_list, hcg):
         parameter_list = [
@@ -834,8 +835,9 @@ def reduce_gradients(self, parameter_list, hcg):
         with framework.no_grad():
             for comm_buffer in self._comm_buffer_list:
                 if self.sd_release_grads and comm_buffer.grad_storage is None:
-                    for param in comm_buffer.params:
-                        comm_buffer._copy_grad_to_buffer(param)
+                    if comm_buffer.need_reduce_scale_sync():
+                        for param in comm_buffer.params:
+                            comm_buffer._copy_grad_to_buffer(param)
 
             if g_sharding_v2_check_zero_padding:
                 self._check_padding_zero()

python/paddle/distributed/fleet/utils/tensor_fusion_helper.py

@@ -553,6 +553,9 @@ def _copy_grad_to_buffer(self, param):
             )
 
         grad_var = param.main_grad if self.use_main_grad else param.grad
+        assert (
+            grad_var is not None
+        ), f"The current parameter[{param.name}] has no gradient, its stop_grdient is {param.stop_gradient}"
         grad_var.stop_gradient = True
         grad_var.flatten_()