Fix transformer kernel CUDA illegal memory access error (#765)

csrc/transformer/ds_transformer_cuda.cpp

@@ -877,7 +877,11 @@ std::vector<torch::Tensor> ds_transformer_backward(int layer_id,
         seq_len = g_output.size(1);
         layer->SetSeqLength(seq_len);
     }
-
+    auto options = torch::TensorOptions()
+                       .dtype(g_output.options().dtype())
+                       .layout(torch::kStrided)
+                       .device(torch::kCUDA)
+                       .requires_grad(true);
     auto workspace = torch::empty({get_workspace_size<T>(bsz,
                                                          seq_len,
                                                          layer->GetHiddenSize(),
@@ -885,7 +889,7 @@ std::vector<torch::Tensor> ds_transformer_backward(int layer_id,
                                                          layer->GetNumHeads(),
                                                          layer->IsTrainingMode(),
                                                          layer->GeluCheckpoint())},
-                                  grad_output.options());
+                                  options);
     Context::Instance().SetWorkSpace((T*)workspace.data_ptr());
 
     auto grad_input = torch::empty_like(input);