update pipelining tutorial (#3182)

* update pipelining tutorial

* Update intermediate_source/pipelining_tutorial.rst

Co-authored-by: Svetlana Karslioglu <svekars@meta.com>

* Update intermediate_source/pipelining_tutorial.rst

Co-authored-by: Svetlana Karslioglu <svekars@meta.com>

* Update intermediate_source/pipelining_tutorial.rst

Co-authored-by: Svetlana Karslioglu <svekars@meta.com>

---------

Co-authored-by: Svetlana Karslioglu <svekars@meta.com>

Author: H-Huang

intermediate_source/pipelining_tutorial.rst

@@ -67,7 +67,7 @@ chunks. First, let us define the model:
                h = layer(h, h)
 
          h = self.norm(h) if self.norm else h
-         output = self.output(h).float() if self.output else h
+         output = self.output(h).clone() if self.output else h
          return output
 
 Then, we need to import the necessary libraries in our script and initialize the distributed training process. In this case, we are defining some global variables to use
@@ -109,32 +109,29 @@ Step 1: Partition the Transformer Model
 There are two different ways of partitioning the model:
 
 First is the manual mode in which we can manually create two instances of the model by deleting portions of
-attributes of the model. In this example for a 2 stage (2 ranks) the model is cut in half.
+attributes of the model. In this example for two stages (2 ranks), the model is cut in half.
 
 .. code:: python
 
-   def manual_model_split(model, example_input_microbatch, model_args) -> PipelineStage:
+   def manual_model_split(model) -> PipelineStage:
       if stage_index == 0:
          # prepare the first stage model
          for i in range(4, 8):
                del model.layers[str(i)]
          model.norm = None
          model.output = None
-         stage_input_microbatch = example_input_microbatch
 
       elif stage_index == 1:
          # prepare the second stage model
          for i in range(4):
                del model.layers[str(i)]
          model.tok_embeddings = None
-         stage_input_microbatch = torch.randn(example_input_microbatch.shape[0], example_input_microbatch.shape[1], model_args.dim)
 
       stage = PipelineStage(
          model,
          stage_index,
          num_stages,
          device,
-         input_args=stage_input_microbatch,
       )
       return stage
 
@@ -181,18 +178,19 @@ as well as multiple-stage-per-rank schedules such as ``Interleaved1F1B`` and ``L
       example_input_microbatch = x.chunk(num_microbatches)[0]
 
       # Option 1: Manual model splitting
-      stage = manual_model_split(model, example_input_microbatch, model_args)
+      stage = manual_model_split(model)
 
       # Option 2: Tracer model splitting
       # stage = tracer_model_split(model, example_input_microbatch)
 
+      model.to(device)
       x = x.to(device)
       y = y.to(device)
 
       def tokenwise_loss_fn(outputs, targets):
          loss_fn = nn.CrossEntropyLoss()
-         outputs = outputs.view(-1, model_args.vocab_size)
-         targets = targets.view(-1)
+         outputs = outputs.reshape(-1, model_args.vocab_size)
+         targets = targets.reshape(-1)
          return loss_fn(outputs, targets)
 
       schedule = ScheduleGPipe(stage, n_microbatches=num_microbatches, loss_fn=tokenwise_loss_fn)
@@ -202,6 +200,7 @@ as well as multiple-stage-per-rank schedules such as ``Interleaved1F1B`` and ``L
       elif rank == 1:
          losses = []
          output = schedule.step(target=y, losses=losses)
+         print(f"losses: {losses}")
       dist.destroy_process_group()
 
 In the example above, we are using the manual method to split the model, but the code can be uncommented to also try the
@@ -232,5 +231,10 @@ We discussed two methods of model partitioning, manual and tracer-based, and dem
 micro-batches across different stages. Finally, we covered the execution of the pipeline schedule and the launch of distributed
 processes using ``torchrun``.
 
-For a production ready usage of pipeline parallelism as well as composition with other distributed techniques, see also
+Additional Resources
+--------------------
+
+We have successfully integrated ``torch.distributed.pipelining`` into the `torchtitan repository <https://github.com/pytorch/torchtitan>`__. TorchTitan is a clean, minimal code base for
+large-scale LLM training using native PyTorch. For a production ready usage of pipeline
+parallelism as well as composition with other distributed techniques, see
 `TorchTitan end to end example of 3D parallelism <https://github.com/pytorch/torchtitan>`__.