[dtensor][experiment] experimenting with displaying distributed model…

… parameters and printing sharding info (#127987)

**Summary**
Example code to display distributed model parameters and verify them against ground truth. Also prints sharding information.

**Test Plan**
torchrun --standalone --nnodes=1 --nproc-per-node=4 torch/distributed/_tensor/examples/display_sharding_example.py

Pull Request resolved: #127987
Approved by: https://github.com/XilunWu
ghstack dependencies: #127358, #127360, #127630

torch/distributed/_tensor/debug/comm_mode.py

@@ -61,6 +61,7 @@ class ModuleParamaterShardingTracker(ModuleTracker):
     def __init__(self):
         super().__init__()
         self.module_parameters_dict = {}
+        self.sharding_dict = {}
 
     def _fw_pre_hook(self, mod, input):
         name = super()._get_mod_name(mod)
@@ -77,14 +78,26 @@ def _fw_pre_hook(self, mod, input):
 
             self.module_parameters_dict[name][param_name] = param.data
 
+            if isinstance(param.data, DTensor):
+                key_name = name + "." + param_name
+                self.sharding_dict[key_name] = param.data.placements
+
     def __enter__(self):
         self.module_parameters_dict.clear()
+        self.sharding_dict.clear()
         self._fw_pre_handle = register_module_forward_pre_hook(self._fw_pre_hook)
         self._fw_post_handle = register_module_forward_hook(super()._fw_post_hook)
 
     def __exit__(self, *args):
         super().__exit__(*args)
 
+    def print_paramater_info(self):
+        print(self.module_parameters_dict)
+
+    def print_sharding_info(self):
+        for key, value in self.sharding_dict.items():
+            print(key + ": " + str(value))
+
 
 class CommDebugMode(TorchDispatchMode):
     """
@@ -130,6 +143,9 @@ def get_comm_counts(self) -> Dict[Any, int]:
     def get_parameter_info(self) -> Dict[str, Dict[str, Any]]:
         return self.advanced_module_tracker.module_parameters_dict
 
+    def get_sharding_info(self) -> Dict[str, Dict[str, Any]]:
+        return self.advanced_module_tracker.sharding_dict
+
     def __enter__(self):
         self.comm_counts.clear()
         super().__enter__()
@@ -140,6 +156,12 @@ def __exit__(self, *args):
         self.advanced_module_tracker.__exit__()
         super().__exit__(*args)
 
+    def print_paramater_info(self):
+        self.advanced_module_tracker.print_paramater_info()
+
+    def print_sharding_info(self):
+        self.advanced_module_tracker.print_sharding_info()
+
     def __torch_dispatch__(self, func, types, args=(), kwargs=None):
         # When running this mode with DTensor, ordinarily all modes will
         # run **before** subclasses get a chance to run.

torch/distributed/_tensor/examples/display_sharding_example.py

@@ -1,23 +1,50 @@
+import os
 from typing import Any, Dict
 
 import torch
 
+from torch.distributed._tensor import DeviceMesh, Shard
 from torch.distributed._tensor.debug import CommDebugMode
-
 from torch.distributed._tensor.debug.comm_mode import ModuleParamaterShardingTracker
 
+from torch.distributed.tensor.parallel import (
+    ColwiseParallel,
+    parallelize_module,
+    RowwiseParallel,
+)
+
 from torch.testing._internal.distributed._tensor.common_dtensor import (
     MLPModule,
     MLPStacked,
+    NUM_DEVICES,
 )
 
 
+def get_device_type():
+    return (
+        "cuda"
+        if torch.cuda.is_available() and torch.cuda.device_count() >= 4
+        else "cpu"
+    )
+
+
+c10d_functional = torch.ops.c10d_functional
+
+aten = torch.ops.aten
+supported_ops = [aten.view.default, aten._to_copy.default]
+
+
 class DisplayShardingExample:
     """
     Checks if the set of keys in ground truth dictionary and the set
     produced in advanced_module_tracker are in the same order
     """
 
+    def __init__(self, world_size, rank):
+        self.world_size = world_size
+        self.rank = rank
+        self.device_type = get_device_type()
+
     def same_set_of_keys(self, dict1, dict2):
         dict1_keys = []
         dict2_keys = []
@@ -54,9 +81,7 @@ def ground_truth(self, model):
         return module_parameters_dict
 
     def test_display_parameters_MLP(self):
-        """
-        Example of using obtaining all module's FQN and parameters for a given model
-        """
+        """Example of obtaining all module's FQN and parameters for a given model"""
 
         inp_size = [8, 10]
 
@@ -67,7 +92,6 @@ def test_display_parameters_MLP(self):
 
         LR = 0.25
 
-        optim = torch.optim.SGD(model.parameters(), lr=LR)
         comm_mode = CommDebugMode()
         module_tracker = ModuleParamaterShardingTracker()
 
@@ -91,7 +115,61 @@ def test_display_parameters_MLP(self):
             )
         )
 
+    def test_display_parameters_MLP_distributed(
+        self, is_seq_parallel=False, recompute_activation=False
+    ):
+        "Example of obtaining all module's FQN and parameters for a given distributed model and printing the sharding info"
+        device_mesh = DeviceMesh(
+            self.device_type,
+            torch.arange(0, NUM_DEVICES),
+        )
+        inp_size = [8, 10]
+        rng_seed = self.rank if is_seq_parallel else 0
+        torch.manual_seed(rng_seed)
+        inp = torch.rand(*inp_size, device=self.device_type)
+        model = MLPModule(self.device_type)
+
+        LR = 0.25
+
+        parallelize_plan = {
+            "net1": ColwiseParallel(input_layouts=Shard(0))
+            if is_seq_parallel
+            else ColwiseParallel(),
+            "net2": RowwiseParallel(output_layouts=Shard(0))
+            if is_seq_parallel
+            else RowwiseParallel(),
+        }
+
+        model = parallelize_module(model, device_mesh, parallelize_plan)
+
+        comm_mode = CommDebugMode()
+
+        with comm_mode:
+            output_tp = model(inp)
+            output_tp.sum().backward()
+
+        print(
+            self.same_set_of_keys(
+                self.ground_truth(model), comm_mode.get_parameter_info()
+            )
+        )
+
+        comm_mode.print_sharding_info()
+
+
+def run_example(world_size, rank):
+    # set manual seed
+    torch.manual_seed(0)
+
+    # run the example
+    instantiated_test = DisplayShardingExample(world_size, rank)
+    instantiated_test.test_display_parameters_MLP_distributed()
+
 
 if __name__ == "__main__":
-    instantiated_test = DisplayShardingExample()
-    instantiated_test.test_display_parameters_MLP()
+    # this script is launched via torchrun which automatically manages ProcessGroup
+    rank = int(os.environ["RANK"])
+    world_size = int(os.environ["WORLD_SIZE"])
+    assert world_size == 4  # our example uses 4 worker ranks
+
+    run_example(world_size, rank)