Add LayerSpec Support to ORTPipelineModule (microsoft#20410)

### Description
In Deepspeed's Pipeline Parallel Implementation, there is a class used
to instantiate the object after it's moved to the device and assigned in
a stage.

This approach helps reduce peak memory usage. 

In this PR, we're adding support to ORT for wrapping this LayerSpec.

orttraining/orttraining/python/training/ortmodule/experimental/pipe/_ort_pipeline_module.py

@@ -142,6 +142,18 @@ def _build(self):
             elif isinstance(layer, LayerSpec):
                 module = layer.build()
                 name = str(layer_idx)
+
+                if "debug_options" in self.ort_kwargs:
+                    new_onnx_prefix = name + "_" + self.ort_kwargs["debug_options"].onnx_prefix
+                    parallel_debug_options = DebugOptions(
+                        self.ort_kwargs["debug_options"].log_level,
+                        self.ort_kwargs["debug_options"].save_onnx,
+                        new_onnx_prefix,
+                    )
+                    module = ORTModule(module, parallel_debug_options)
+                else:
+                    module = ORTModule(module)
+
                 self.forward_funcs.append(module)
                 self.fwd_map.update({name: len(self.forward_funcs) - 1})
                 self.add_module(name, module)

orttraining/orttraining/test/python/orttraining_ortmodule_distributed_tests.py

@@ -56,7 +56,7 @@ def run_ortmodule_deepspeed_pipeline_parallel_tests(cwd, log):
     run_subprocess(command, cwd=cwd, log=log).check_returncode()
 
 
-def run_ort_pipeline_module_tests(cwd, log):
+def run_ort_pipeline_module_tests(cwd, log, layer_spec_flag=False):
     log.debug("Running: ORTPipelineModule tests")
 
     command = [
@@ -66,6 +66,9 @@ def run_ort_pipeline_module_tests(cwd, log):
         "orttraining_test_ortmodule_deepspeed_pipeline_parallel_config.json",
     ]
 
+    if layer_spec_flag:
+        command.append("--layer_spec=True")
+
     run_subprocess(command, cwd=cwd, log=log).check_returncode()
 
 
@@ -107,7 +110,11 @@ def main():
     run_ortmodule_deepspeed_zero_stage_1_tests(cwd, log, args.mnist)
 
     run_ortmodule_deepspeed_pipeline_parallel_tests(cwd, log)
+
+    # Deepspeed ORTPipelineModule Tests
     run_ort_pipeline_module_tests(cwd, log)
+    run_ort_pipeline_module_tests(cwd, log, layer_spec_flag=True)
+
     run_ortmodule_fairscale_sharded_optimizer_tests(cwd, log, args.mnist)
 
     run_distributed_cache_test(cwd, log)

orttraining/orttraining/test/python/orttraining_test_ort_pipeline_module.py

@@ -1,90 +1,135 @@
 import argparse
+from typing import Dict, Tuple
 
 import deepspeed
 import torch
-from torch import nn
+from deepspeed.pipe import LayerSpec
+from torch import nn, utils
 
 from onnxruntime.training.ortmodule.experimental.pipe import ORTPipelineModule
 
+# This script demonstrates how to set up a pipeline parallel training session
+# using DeepSpeed's ORTPipelineModule for a simple neural network model.
+
+
 # USAGE:
 # pip install deepspeed
 # deepspeed orttraining_test_ort_pipeline_module.py --deepspeed_config=orttraining_test_ortmodule_deepspeed_pipeline_parallel_config.json --pipeline-parallel-size 2 --steps=100
-# expected output : steps: 100 loss: 0.0585 iter time (s): 0.186 samples/sec: 53.694
+def get_args() -> argparse.Namespace:
+    """Parse and return command line arguments."""
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--local_rank", type=int, default=-1, help="Local rank passed from distributed launcher")
+    parser.add_argument("--steps", type=int, default=100, help="Number of training steps to run")
+    parser.add_argument("--pipeline-parallel-size", type=int, default=2, help="Number of pipeline stages")
+    parser.add_argument("--backend", type=str, default="nccl", help="Distributed backend")
+    parser.add_argument("--seed", type=int, default=0, help="Random seed for reproducibility")
+    parser.add_argument("--layer_spec", type=bool, default=False, help="Use LayerSpec for layer specification")
+
+    parser = deepspeed.add_config_arguments(parser)
+    return parser.parse_args()
+
 
+class SampleData(utils.data.Dataset):
+    """Custom dataset to facilitate loading and batching of data."""
 
-class SampleData(torch.utils.data.Dataset):
-    def __init__(self, x, y):
+    def __init__(self, x: torch.Tensor, y: torch.Tensor):
         self.x = x
         self.y = y
 
-    def __len__(self):
-        return x.size()[0]
+    def __len__(self) -> int:
+        return self.x.size(0)
 
-    def __getitem__(self, idx):
+    def __getitem__(self, idx: int) -> Tuple[torch.Tensor, torch.Tensor]:
         return self.x[idx], self.y[idx]
 
 
-def get_args():
-    parser = argparse.ArgumentParser()
-    parser.add_argument("--local_rank", type=int, default=-1, help="local rank passed from distributed launcher")
-    parser.add_argument("-s", "--steps", type=int, default=100, help="quit after this many steps")
-    parser.add_argument("-p", "--pipeline-parallel-size", type=int, default=2, help="pipeline parallelism")
-    parser.add_argument("--backend", type=str, default="nccl", help="distributed backend")
-    parser.add_argument("--seed", type=int, default=0, help="PRNG seed")
-    parser.add_argument("--fp16", type=bool, default=False, help="fp16 run")
+class SimpleNetPipeInput(nn.Module):
+    """First stage of the pipeline, responsible for initial processing."""
 
-    parser = deepspeed.add_config_arguments(parser)
-    args = parser.parse_args()
-    return args
+    def __init__(self, config: Dict[str, int]):
+        super().__init__()
+        self.linear = nn.Linear(config["input_size"], config["hidden_size"])
+        self.activation = nn.ReLU()
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        x = self.linear(x)
+        x = self.activation(x)
+        return x
+
+
+class SimpleNetPipeBlock(nn.Module):
+    """Intermediate stage of the pipeline, can be duplicated to deepen the network."""
+
+    def __init__(self, config: Dict[str, int]):
+        super().__init__()
+        self.linear = nn.Linear(config["hidden_size"], config["hidden_size"])
+        self.activation = nn.ReLU()
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        x = self.linear(x)
+        x = self.activation(x)
+        return x
+
+
+class SimpleNetPipeOutput(nn.Module):
+    """Final stage of the pipeline, producing the output."""
+
+    def __init__(self, config: Dict[str, int]):
+        super().__init__()
+        self.linear = nn.Linear(config["hidden_size"], config["output_size"])
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        x = self.linear(x)
+        return x
+
+
+def build_model(config: Dict[str, int], n: int, layer_spec: bool) -> nn.Module:
+    """Constructs and returns the model either using LayerSpec or nn.Sequential."""
+    if layer_spec:
+        print("Wrapping layers with LayerSpec")
+        model = (
+            [LayerSpec(SimpleNetPipeInput, config)]
+            + [LayerSpec(SimpleNetPipeBlock, config) for _ in range(n)]
+            + [LayerSpec(SimpleNetPipeOutput, config)]
+        )
+    else:
+        print("Wrapping layers with nn.Sequential")
+        model = nn.Sequential(
+            SimpleNetPipeInput(config),
+            SimpleNetPipeBlock(config),
+            SimpleNetPipeBlock(config),
+            SimpleNetPipeOutput(config),
+        )
+    return model
 
 
-n = 10
-d_in = 4
-d_hidden = 8
-d_out = 3
 args = get_args()
 torch.cuda.set_device(args.local_rank)
 device = torch.device("cuda", args.local_rank)
-
-# dist.init_process_group(backend=args.backend)
 deepspeed.init_distributed(dist_backend=args.backend)
 torch.manual_seed(args.seed)
-# Model.
-
-model = nn.Sequential(
-    nn.Linear(d_in, d_hidden),  # Stage 1
-    nn.ReLU(),  # Stage 1
-    nn.Linear(d_hidden, d_hidden),  # Stage 1
-    nn.ReLU(),  # Stage 1
-    nn.Linear(d_hidden, d_hidden),  # Stage 2
-    nn.ReLU(),  # Stage 2
-    nn.Linear(d_hidden, d_out),  # Stage 2
-)
+
+model = build_model({"input_size": 4, "hidden_size": 8, "output_size": 3}, n=10, layer_spec=args.layer_spec)
 
 model = ORTPipelineModule(
     layers=model,
     loss_fn=torch.nn.CrossEntropyLoss(),
     num_stages=args.pipeline_parallel_size,
-    partition_method="uniform",  #'parameters',
+    partition_method="uniform",
     activation_checkpoint_interval=0,
 )
 
-params = [p for p in model.parameters() if p.requires_grad]
-
-# Input.
-x = torch.rand((n, d_in))
-if args.fp16:
-    x = x.half()
-# Output.
-y = torch.randint(0, d_out, (n,))
-ds = SampleData(x, y)
+# Setup input data
+x = torch.rand((10, 4))
+y = torch.randint(0, 3, (10,))
+dataset = SampleData(x, y)
 
 print("Initialize deepspeed")
 model_engine, optimizer, _, _ = deepspeed.initialize(
-    args=args, model=model, model_parameters=params, training_data=ds  # (x,y)#
+    args=args, model=model, model_parameters=model.parameters(), training_data=dataset
 )
 
 for step in range(args.steps):
     loss = model_engine.train_batch()
     if step % 10 == 0:
-        print("step = ", step, ", loss = ", loss)
+        print(f"step = {step}, loss = {loss}")