Fix for stage3 when setting different communication data type (micros…

…oft#4540)

Co-authored-by: Olatunji Ruwase <[email protected]>

deepspeed/runtime/zero/stage3.py

@@ -1217,7 +1217,7 @@ def __reduce_and_partition_ipg_grads(self, safe_mode: bool = False) -> None:
     @instrument_w_nvtx
     def __avg_scatter_contiguous_grads(self, buffer_to_reduce: Tensor) -> List[Tensor]:
         dtype = buffer_to_reduce.dtype
-        if self.communication_data_type == self.dtype:
+        if self.communication_data_type != dtype:
             buffer_to_reduce = buffer_to_reduce.to(self.communication_data_type)
         if self.postscale_gradients and self.gradient_predivide_factor != 1.0:
             buffer_to_reduce = buffer_to_reduce.div_(self.gradient_predivide_factor)