[dtensor] updated api and doc (#3845)

colossalai/device/README.md

+# 🗄 Device
+
+## 📚 Table of Contents
+
+- [🗄 Device](#-device)
+  - [📚 Table of Contents](#-table-of-contents)
+  - [🔗 Introduction](#-introduction)
+  - [📝 Design](#-design)
+  - [🔨 Usage](#-usage)
+
+## 🔗 Introduction
+
+This module contains the implementation of the abstraction of the device topology. It is used to represent the device topology and manage the distributed information related to the network.
+
+## 📝 Design
+
+
+This module is inspired by the DeviceMesh in the [Alpa project](https://github.com/alpa-projects/alpa) and the device array can be represented as a 1D or 2D mesh. We will be extending the device mesh to support 3D mesh in the future.
+
+
+## 🔨 Usage
+
+- Create a device mesh
+
+```python
+# this is the list of global ranks involved in the device mesh
+# assume we have 4 GPUs and the global ranks for these GPUs are 0, 1, 2, 3
+physical_mesh_id = torch.arange(4)
+mesh_shape = [2, 2]
+device_mesh = DeviceMesh(physical_mesh_id, mesh_shape)
+```
+
+- View the mesh
+
+
+```python
+# view the mesh shape
+# expect output
+# [2, 2]
+print(device_mesh.shape)
+
+
+# view the logical mesh with global ranks
+# expect output
+# [
+#   [0, 1],
+#   [2, 3]
+# ]
+print(device_mesh.logical_mesh_id)
+
+# view the number of devices in the mesh
+# expect output
+# 4
+print(device_mesh.num_devices)
+
+```
+
+- Initialize the process group
+
+```python
+# intialize process group
+device_mesh.init_logical_process_group()
+
+
+# get the process group for a rank with respect to an axis
+# this is the process group involving global ranks 0 and 2
+print(device_mesh.get_process_group(axis=0, global_rank=0))
+
+# get the ranks in the process with respect to an axis
+# expect output
+# [0, 2]
+print(device_mesh.get_ranks_in_process_group(axis=0, global_rank=0))
+```

colossalai/lazy/lazy_init.py

 from types import MethodType
-from typing import Callable, Optional, Union
+from typing import Callable, Dict, Optional, Union
 
 import torch
 import torch.distributed as dist
@@ -8,8 +8,9 @@ from torch import Tensor
 from torch.utils._pytree import tree_map
 
 from colossalai._analyzer._subclasses import MetaTensor
+from colossalai.device.device_mesh import DeviceMesh
 from colossalai.tensor.d_tensor.d_tensor import DTensor
-from colossalai.tensor.d_tensor.layout import Layout
+from colossalai.tensor.d_tensor.sharding_spec import ShardingSpec
 
 # reference: https://pytorch.org/cppdocs/notes/tensor_creation.html
 _NORMAL_FACTORY = [
@@ -172,7 +173,7 @@ class LazyTensor(torch.Tensor):
         self.clean()
         return _convert_cls(self, target)
 
-    def distribute(self, layout: Layout) -> torch.Tensor:
+    def distribute(self, device_mesh: DeviceMesh, sharding_spec: ShardingSpec) -> torch.Tensor:
         """Distribute the ``LazyTensor`` to ``torch.Tensor`` by modifying __class__ (inplace), according to the layout.
 
         Args:
@@ -183,7 +184,7 @@ class LazyTensor(torch.Tensor):
         """
         target = self._materialize_data()
         self.clean()
-        local_tensor = DTensor(target, layout).local_tensor
+        local_tensor = DTensor(target, device_mesh, sharding_spec).local_tensor
         return _convert_cls(self, local_tensor)
 
     def clean(self) -> None:
@@ -536,7 +537,10 @@ class LazyInitContext:
         return _apply_to_lazy_module(module, apply_fn, verbose)
 
     @staticmethod
-    def distribute(module: nn.Module, layout_dict: dict, verbose: bool = False) -> nn.Module:
+    def distribute(module: nn.Module,
+                   device_mesh: DeviceMesh,
+                   sharding_spec_dict: Dict[str, ShardingSpec],
+                   verbose: bool = False) -> nn.Module:
         """Distribute all ``nn.Parameter`` from ``LazyTensor``. This function will modify the module in-place.
 
         Args:
@@ -546,7 +550,7 @@ class LazyInitContext:
         """
 
         def apply_fn(name: str, p: LazyTensor):
-            p.distribute(layout_dict[name])
+            p.distribute(device_mesh, sharding_spec_dict[name])
 
         return _apply_to_lazy_module(module, apply_fn, verbose)
 

colossalai/tensor/comm_spec.py

@@ -16,69 +16,66 @@ def _all_gather(tensor, comm_spec):
     '''
     Implement all gather operation on device mesh based on information provided by comm_spec.
     '''
-    process_groups_list = comm_spec.device_mesh.process_groups_dict[comm_spec.logical_process_axis]
-    for rank_list, process_group in process_groups_list:
-        if dist.get_rank() in rank_list:
-            tensor_list = [
-                torch.zeros(tensor.shape, dtype=tensor.dtype, device=tensor.device)
-                for _ in range(comm_spec.device_mesh.mesh_shape[comm_spec.logical_process_axis])
-            ]
-            # without this contiguous operation, the all gather may get some unexpected results.
-            tensor = tensor.contiguous()
-            dist.all_gather(tensor_list, tensor, group=process_group)
-            output = torch.cat(tuple(tensor_list), comm_spec.gather_dim).contiguous()
-            return output
+    process_groups = comm_spec.device_mesh.get_process_group_for_all_axes()
+    process_group = process_groups[comm_spec.logical_process_axis]
+
+    tensor_list = [
+        torch.zeros(tensor.shape, dtype=tensor.dtype, device=tensor.device)
+        for _ in range(comm_spec.device_mesh.mesh_shape[comm_spec.logical_process_axis])
+    ]
+    # without this contiguous operation, the all gather may get some unexpected results.
+    tensor = tensor.contiguous()
+    dist.all_gather(tensor_list, tensor, group=process_group)
+    output = torch.cat(tuple(tensor_list), comm_spec.gather_dim).contiguous()
+    return output
 
 
 def _split(tensor, comm_spec):
     '''
     Implement shard operation on device mesh based on information provided by comm_spec.
     '''
-    process_groups_list = comm_spec.device_mesh.process_groups_dict[comm_spec.logical_process_axis]
-    for rank_list, _ in process_groups_list:
-        if dist.get_rank() in rank_list:
-            dim = comm_spec.shard_dim
-            length = tensor.shape[comm_spec.shard_dim] // len(rank_list)
-            start = length * rank_list.index(dist.get_rank())
-            output = torch.narrow(tensor, dim, start, length).contiguous()
-            return output
+    process_groups = comm_spec.device_mesh.get_process_group_for_all_axes()
+    process_group = process_groups[comm_spec.logical_process_axis]
+
+    dim = comm_spec.shard_dim
+    length = tensor.shape[comm_spec.shard_dim] // dist.get_world_size(process_group)
+    start = length * dist.get_rank(process_group)
+    output = torch.narrow(tensor, dim, start, length).contiguous()
+    return output
 
 
 def _all_to_all(tensor, comm_spec):
     '''
     Implement all to all operation on device mesh based on information provided by comm_spec.
     '''
-    process_groups_list = comm_spec.device_mesh.process_groups_dict[comm_spec.logical_process_axis]
-    for rank_list, process_group in process_groups_list:
-        if dist.get_rank() in rank_list:
-            new_shape = list(tensor.shape)
-            new_shape[comm_spec.shard_dim] = new_shape[comm_spec.shard_dim] // len(rank_list)
-            new_shape = torch.Size(new_shape)
-            output_tensor_list = [
-                torch.zeros(new_shape, dtype=tensor.dtype, device=tensor.device) for _ in range(len(rank_list))
-            ]
-            dim = comm_spec.shard_dim
-            length = tensor.shape[comm_spec.shard_dim] // len(rank_list)
-            input_tensor_list = [
-                torch.narrow(tensor, dim, length * i, length).contiguous() for i in range(len(rank_list))
-            ]
-            group = process_group
-            dist.all_to_all(output_tensor_list, input_tensor_list, group)
-            output = torch.cat(tuple(output_tensor_list), comm_spec.gather_dim).contiguous()
-            return output
+    process_groups = comm_spec.device_mesh.get_process_group_for_all_axes()
+    process_group = process_groups[comm_spec.logical_process_axis]
+    world_size = dist.get_world_size(process_group)
+
+    new_shape = list(tensor.shape)
+    new_shape[comm_spec.shard_dim] = new_shape[comm_spec.shard_dim] // world_size
+    new_shape = torch.Size(new_shape)
+    output_tensor_list = [torch.zeros(new_shape, dtype=tensor.dtype, device=tensor.device) for _ in range(world_size)]
+    dim = comm_spec.shard_dim
+    length = tensor.shape[comm_spec.shard_dim] // world_size
+    input_tensor_list = [torch.narrow(tensor, dim, length * i, length).contiguous() for i in range(world_size)]
+    group = process_group
+    dist.all_to_all(output_tensor_list, input_tensor_list, group)
+    output = torch.cat(tuple(output_tensor_list), comm_spec.gather_dim).contiguous()
+    return output
 
 
 def _all_reduce(tensor, comm_spec, async_op=False):
     '''
     Implement all reduce operation on device mesh based on information provided by comm_spec.
     '''
-    process_groups_list = comm_spec.device_mesh.process_groups_dict[comm_spec.logical_process_axis]
-    for rank_list, process_group in process_groups_list:
-        if dist.get_rank() in rank_list:
-            if not tensor.is_contiguous():
-                tensor = tensor.contiguous()
-            dist.all_reduce(tensor, op=ReduceOp.SUM, group=process_group, async_op=async_op)
-            return tensor
+    process_groups = comm_spec.device_mesh.get_process_group_for_all_axes()
+    process_group = process_groups[comm_spec.logical_process_axis]
+
+    if not tensor.is_contiguous():
+        tensor = tensor.contiguous()
+    dist.all_reduce(tensor, op=ReduceOp.SUM, group=process_group, async_op=async_op)
+    return tensor
 
 
 def _mix_gather(tensor, comm_spec):
@@ -414,7 +411,7 @@ class CommSpec:
         self.forward_only = forward_only
         if isinstance(self.logical_process_axis, list):
             if not mix_gather:
-                self.device_mesh = self.sharding_spec.device_mesh.flatten_device_mesh
+                self.device_mesh = self.sharding_spec.device_mesh.flatten()
                 self.logical_process_axis = 0
             else:
                 self.device_meshes = self.sharding_spec.device_mesh.flatten_device_meshes

colossalai/tensor/d_tensor/RAEDME.md

+# 🔢 Distributed Tensor
+
+## 📚 Table of Contents
+
+- [🔢 Distributed Tensor](#-distributed-tensor)
+  - [📚 Table of Contents](#-table-of-contents)
+  - [🔗 Introduction](#-introduction)
+  - [📝 Design](#-design)
+  - [🔨 Usage](#-usage)
+  - [🎈 Progress Log](#-progress-log)
+
+## 🔗 Introduction
+
+Distributed tensor is a type of tensor that is distributed across multiple devices. It is a wrapper of PyTorch tensor, and it is used to support distributed training.
+It can represent the device topology and tensor placement over the devices in the topology. It also provides a set of APIs to manipulate the distributed tensor.
+
+## 📝 Design
+
+Our implementation is inspired by the work [Alpa](https://arxiv.org/abs/2201.12023), which unifies data parallelism and tensor parallelism as intra-op parallelism. It uses notations `S` to represent the sharded dimension and `R` to represent the replicated dimension. For example, given a 2D matrix, `[S, R]` represents the tensor is sharded over the first dimension.
+
+Each sharded dimension will have a subscript to represent its placement over the devices. Assuming we have 4 GPUs and the GPUs are arranged in a 2 x 2 manner. Let's say we have a 2D matrix like below:
+
+
+```text
+    [1,  2,  3,  4 ]
+A = [4,  5,  6,  7 ]
+    [8,  9,  10, 11]
+    [12, 13, 14, 15]
+```
+
+`[S0, R]` would mean that the first dimension is sharded over the rows in the device topology.
+
+```text
+| --------------------—————————————————————-|
+|                     |                     |
+|  [1,  2,  3,  4 ]   |  [1,  2,  3,  4 ]   |
+|  [4,  5,  6,  7 ]   |  [4,  5,  6,  7 ]   |
+|                     |                     |
+| --------------------——————————————————-----
+|                     |                     |
+|  [8,  9,  10, 11]   |  [8,  9,  10, 11]   |
+|  [12, 13, 14, 15]   |  [12, 13, 14, 15]   |
+|                     |                     |
+| --------------------——————————————————-----
+```
+
+`[S01, R]` would mean that the first dimension is sharded over both the row and column in the device topology.
+
+```text
+| --------------------—————————————————————-|
+|                     |                     |
+|  [1,  2,  3,  4 ]   |  [4,  5,  6,  7 ]   |
+|                     |                     |
+| --------------------——————————————————-----
+|                     |                     |
+|  [8,  9,  10, 11]   |  [12, 13, 14, 15]   |
+|                     |                     |
+| --------------------——————————————————-----
+```
+
+## 🔨 Usage
+
+A sample API usage is given below.
+
+```python
+import torch
+
+import colossalai
+from colossalai.device.device_mesh import DeviceMesh
+from colossalai.tensor.d_tensor import DTensor, ShardingSpec
+
+colossalai.launch_from_torch(config={})
+
+# define your device mesh
+# assume you have 4 GPUs
+physical_mesh_id = torch.arange(0, 4).reshape(1, 4)
+mesh_shape = (2, 2)
+device_mesh = DeviceMesh(physical_mesh_id, mesh_shape, init_process_group=True)
+
+# define a tensor
+a = torch.rand(16, 32).cuda()
+
+# create sharding spec for the tensor
+# assume the sharding spec is [S0, R]
+dim_partition_dict = {0: [0]}
+sharding_spec = ShardingSpec(a.dim(), dim_partition_dict)
+
+# create a distributed tensor
+d_tensor = DTensor(a, device_mesh, sharding_spec)
+print(d_tensor)
+
+global_tensor = d_tensor.to_global()
+print(global_tensor)
+```
+
+
+## 🎈 Progress Log
+
+- [x] Support layout conversion
+- [x] Support sharding on 2D device mesh
+- [ ] Support sharding on 3D device mesh
+- [ ] Support sharding 4D device mesh
+- [ ] Support sharding info saving and offline tensor merge (we can save tensor as dtensor and gather the tensors back to the global tensor based on the sharding info in a single process in CPU, useful for distributed training checkpoint load and save.)

colossalai/tensor/d_tensor/__init__.py

+from .d_tensor import DTensor
+from .sharding_spec import ShardingSpec
+
+__all__ = ['DTensor', 'ShardingSpec']

colossalai/tensor/d_tensor/comm_spec.py

@@ -24,12 +24,12 @@ class CommSpec:
     '''
     Communication spec is used to record the communication action. It converts the communication spec
     to real action which will be used in runtime. It contains comm_pattern to determine the
-    communication method, process_groups_dict to determine the process groups, gather_dim and shard_dim
+    communication method, process_group_dict to determine the process groups, gather_dim and shard_dim
     to determine the buffer shape, and logical_process_axis
 
     Argument:
-        comm_pattern(CollectiveCommPattern): describe the communication method used in this spec.
-        process_groups_dict(Dict): A dict which contains the process groups used to apply this CommSpec.
+        comm_pattern(CollectiveCommPattern): decribe the communication method used in this spec.
+        process_group_dict(Dict): A dict which contains the process groups used to apply this CommSpec.
         gather_dim(int, Optional): The gather_dim of the tensor will be gathered.
         shard_dim(int, Optional): The shard_dim of the tensor will be sharded.
         logical_process_axis(Union(int, List[int]), Optional): The mesh_dim to implement the communication action.
@@ -37,7 +37,7 @@ class CommSpec:
 
     def __init__(self,
                  comm_pattern: CollectiveCommPattern,
-                 process_groups_dict: Dict,
+                 process_group_dict: Dict,
                  gather_dim: int = None,
                  shard_dim: int = None,
                  logical_process_axis: int = None):
@@ -45,7 +45,7 @@ class CommSpec:
         self.gather_dim = gather_dim
         self.shard_dim = shard_dim
         self.logical_process_axis = logical_process_axis
-        self.process_groups_dict = process_groups_dict
+        self.process_group_dict = process_group_dict
 
     def __repr__(self):
         res_list = ["CommSpec:("]
@@ -92,68 +92,56 @@ def _all_gather(tensor: torch.Tensor, comm_spec: CommSpec):
     '''
     Implement all gather operation on device mesh based on information provided by comm_spec.
     '''
-    process_groups_list = comm_spec.process_groups_dict[comm_spec.logical_process_axis]
-    for rank_list, process_group in process_groups_list:
-        if dist.get_rank() in rank_list:
-            tensor_list = [
-                torch.zeros(tensor.shape, dtype=tensor.dtype, device=tensor.device) for _ in range(len(rank_list))
-            ]
-            # without this contiguous operation, the all gather may get some unexpected results.
-            tensor = tensor.contiguous()
-            dist.all_gather(tensor_list, tensor, group=process_group)
-            output = torch.cat(tuple(tensor_list), comm_spec.gather_dim).contiguous()
-            return output
+    process_group = comm_spec.process_group_dict[comm_spec.logical_process_axis]
+    world_size = dist.get_world_size(process_group)
+    tensor_list = [torch.zeros(tensor.shape, dtype=tensor.dtype, device=tensor.device) for _ in range(world_size)]
+    # without this contiguous operation, the all gather may get some unexpected results.
+    tensor = tensor.contiguous()
+    dist.all_gather(tensor_list, tensor, group=process_group)
+    output = torch.cat(tuple(tensor_list), comm_spec.gather_dim).contiguous()
+    return output
 
 
 def _split(tensor: torch.Tensor, comm_spec: CommSpec):
     '''
     Implement shard operation on device mesh based on information provided by comm_spec.
     '''
-    process_groups_list = comm_spec.process_groups_dict[comm_spec.logical_process_axis]
-    for rank_list, _ in process_groups_list:
-        if dist.get_rank() in rank_list:
-            dim = comm_spec.shard_dim
-            length = tensor.shape[comm_spec.shard_dim] // len(rank_list)
-            start = length * rank_list.index(dist.get_rank())
-            output = torch.narrow(tensor, dim, start, length).contiguous()
-            return output
+    process_group = comm_spec.process_group_dict[comm_spec.logical_process_axis]
+    dim = comm_spec.shard_dim
+    length = tensor.shape[comm_spec.shard_dim] // dist.get_world_size(process_group)
+    start = length * dist.get_rank(process_group)
+    output = torch.narrow(tensor, dim, start, length).contiguous()
+    return output
 
 
 def _all_to_all(tensor: torch.Tensor, comm_spec: CommSpec):
     '''
     Implement all to all operation on device mesh based on information provided by comm_spec.
     '''
-    process_groups_list = comm_spec.process_groups_dict[comm_spec.logical_process_axis]
-    for rank_list, process_group in process_groups_list:
-        if dist.get_rank() in rank_list:
-            new_shape = list(tensor.shape)
-            new_shape[comm_spec.shard_dim] = new_shape[comm_spec.shard_dim] // len(rank_list)
-            new_shape = torch.Size(new_shape)
-            output_tensor_list = [
-                torch.zeros(new_shape, dtype=tensor.dtype, device=tensor.device) for _ in range(len(rank_list))
-            ]
-            dim = comm_spec.shard_dim
-            length = tensor.shape[comm_spec.shard_dim] // len(rank_list)
-            input_tensor_list = [
-                torch.narrow(tensor, dim, length * i, length).contiguous() for i in range(len(rank_list))
-            ]
-            group = process_group
-            dist.all_to_all(output_tensor_list, input_tensor_list, group)
-            output = torch.cat(tuple(output_tensor_list), comm_spec.gather_dim).contiguous()
-            return output
+    process_group = comm_spec.process_group_dict[comm_spec.logical_process_axis]
+    world_size = dist.get_world_size(process_group)
+    new_shape = list(tensor.shape)
+    new_shape[comm_spec.shard_dim] = new_shape[comm_spec.shard_dim] // world_size
+    new_shape = torch.Size(new_shape)
+    output_tensor_list = [torch.zeros(new_shape, dtype=tensor.dtype, device=tensor.device) for _ in range(world_size)]
+    dim = comm_spec.shard_dim
+    length = tensor.shape[comm_spec.shard_dim] // world_size
+    input_tensor_list = [torch.narrow(tensor, dim, length * i, length).contiguous() for i in range(world_size)]
+    group = process_group
+    dist.all_to_all(output_tensor_list, input_tensor_list, group)
+    output = torch.cat(tuple(output_tensor_list), comm_spec.gather_dim).contiguous()
+    return output
 
 
 def _all_reduce(tensor: torch.Tensor, comm_spec: CommSpec, async_op: bool = False):
     '''
     Implement all reduce operation on device mesh based on information provided by comm_spec.
     '''
-    process_groups_list = comm_spec.process_groups_dict[comm_spec.logical_process_axis]
-    for rank_list, process_group in process_groups_list:
-        if dist.get_rank() in rank_list:
-            if not tensor.is_contiguous():
-                tensor = tensor.contiguous()
-            dist.all_reduce(tensor, op=ReduceOp.SUM, group=process_group, async_op=async_op)
-            return tensor
+    process_group = comm_spec.process_group_dict[comm_spec.logical_process_axis]
+    if not tensor.is_contiguous():
+        tensor = tensor.contiguous()
+    dist.all_reduce(tensor, op=ReduceOp.SUM, group=process_group, async_op=async_op)
+    return tensor
 
 
 class _ReduceGrad(torch.autograd.Function):
@@ -269,7 +257,7 @@ class _AllToAll(torch.autograd.Function):
     def forward(ctx, input_, comm_spec):
         output = _all_to_all(input_, comm_spec)
         comm_spec_for_backward = CommSpec(comm_pattern=comm_spec.comm_pattern,
-                                          process_groups_dict=comm_spec.process_groups_dict,
+                                          process_group_dict=comm_spec.process_group_dict,
                                           gather_dim=comm_spec.shard_dim,
                                           shard_dim=comm_spec.gather_dim,
                                           logical_process_axis=comm_spec.logical_process_axis)

colossalai/tensor/d_tensor/d_tensor.py

@@ -3,55 +3,119 @@ from typing import Optional
 import torch
 from torch.utils._pytree import tree_map
 
+from colossalai.device.device_mesh import DeviceMesh
+
 from .layout import Layout
 from .layout_converter import LayoutConverter, to_global
 from .sharding_spec import ShardingSpec
 
+__all__ = ['DTensor', 'distribute_tensor', 'distribute_module', 'construct_default_sharding_spec']
+
 layout_converter = LayoutConverter()
 
 
 class DTensor(torch.Tensor):
+    """
+    DTensor stands for distributed tensor. It is a subclass of `torch.Tensor` and contains meta information
+    about the tensor distribution. The meta information includes the device mesh, the sharding specification,
+    and the entire shape of the tensor.
+
+    During runtime, we will not directly use the DTensor objects for computation. Instead, we will only use the
+    `DTensor.local_tensor` for computation. The `DTensor.local_tensor` is the local tensor in the current rank.
+    In this way, all tensors involved in computation will only be native PyTorch tensors.
+
+    Example:
+        ```python
+        from colossalai.device import DeviceMesh
+
+        # define your device mesh
+        # assume you have 4 GPUs
+        physical_mesh_id = torch.arange(0, 4).reshape(1, 4)
+        mesh_shape = (2, 2)
+        device_mesh = DeviceMesh(physical_mesh_id, mesh_shape)
+
+        # define a tensor
+        x = torch.rand(16, 32)
+
+        # create sharding spec for the tensor
+        # assume the sharding spec is [S, R]
+        dim_partition_dict = {
+            0: 1
+        }
+        sharding_spec = ShardingSpec(a.dim(), dim_partition_dict)
+
+        # create a distributed tensor
+        d_tensor = DTensor(x, device_mesh, sharding_spec)
+        ```
 
-    def __init__(self, local_tensor: torch.Tensor, dist_layout: Layout):
-        self.local_tensor = local_tensor
-        self.data_type = local_tensor.dtype
-        self.entire_shape = local_tensor.shape
+    Args:
+        tensor (`torch.Tensor`): the unsharded tensor.
+        device_mesh (`DeviceMesh`): the device mesh for abstraction of the compute devices.
+        sharding_spec (`ShardingSpec`): the sharding specification which describes how the tensor will be sharded.
+    """
+
+    def __init__(self, tensor: torch.Tensor, device_mesh: DeviceMesh, sharding_spec: ShardingSpec):
+        # ensure this tensor is not a DTensor
+        assert not isinstance(tensor, DTensor), 'The input tensor should not be a DTensor.'
+
+        # store meta info
+        self.local_tensor = tensor
+        self.data_type = tensor.dtype
+        self.global_shape = tensor.shape
+
+        # create distributed layout
+        dist_layout = Layout(device_mesh=device_mesh, sharding_spec=sharding_spec, global_shape=self.global_shape)
         self.dist_layout = dist_layout
+
+        # shard the tensor
         self._apply_layout()
 
     @staticmethod
-    def __new__(cls, local_tensor, layout):
-        return torch.Tensor._make_subclass(cls, local_tensor, local_tensor.requires_grad)
+    def __new__(cls, tensor, *args, **kwargs):
+        return torch.Tensor._make_subclass(cls, tensor, tensor.requires_grad)
 
     def __repr__(self):
-        return f"DTensor({self.to_global()}, {self.dist_layout})"
+        return f"DTensor(\n{self.to_global()}\n{self.dist_layout}"
 
     def __str__(self):
         return self.__repr__()
 
-    def layout_convert(self, target_layout):
+    def layout_convert(self, device_mesh: DeviceMesh, sharding_spec: ShardingSpec) -> None:
         '''
         Convert the layout of the tensor from source_spec to target_spec.
+        This will update the `local_tensor` and `dist_layout` in place.
+
+        Args:
+            target_layout (Layout): the target layout specification.
         '''
-        self.local_tensor = layout_converter.apply(self.local_tensor, self.dist_layout, target_layout)
+        target_layout = Layout(device_mesh=device_mesh, sharding_spec=sharding_spec, global_shape=self.global_shape)
+        self.local_tensor = layout_converter.apply(tensor=self.local_tensor,
+                                                   source_layout=self.dist_layout,
+                                                   target_layout=target_layout)
         self.dist_layout = target_layout
 
     def _apply_layout(self):
         '''
         Apply the layout to the local tensor during initializing process.
         '''
+        # layout converter requires a source and target laytout
+        # we construct the source layer for an unsharded tensor
+        # and use self.dist_layer as the targer layout for the sharded tensor
         source_spec = construct_default_sharding_spec(self.local_tensor)
         source_layout = Layout(device_mesh=self.dist_layout.device_mesh,
-                               device_type=self.dist_layout.device_type,
                                sharding_spec=source_spec,
-                               entire_shape=self.entire_shape)
-        self.local_tensor = layout_converter.apply(self.local_tensor, source_layout, self.dist_layout)
+                               global_shape=self.global_shape)
+        self.local_tensor = layout_converter.apply(tensor=self.local_tensor,
+                                                   source_layout=source_layout,
+                                                   target_layout=self.dist_layout)
 
     @classmethod
     def __torch_function__(cls, func, types, args=(), kwargs=None):
         if kwargs is None:
             kwargs = {}
 
+        # convert all DTensors to native pytorch tensors
+        # so that operations will be conducted on native tensors
         def filter_arg(arg):
             if isinstance(arg, DTensor):
                 return arg.local_tensor
@@ -60,9 +124,9 @@ class DTensor(torch.Tensor):
 
         args = tree_map(filter_arg, args)
         kwargs = tree_map(filter_arg, kwargs)
-        # if we want to convert the result into DTensor, we need to infer the layout of result from the layout of input tensors
-        # and op type.
 
+        # NOTE: if we want to convert the result into DTensor, we need to infer the layout of result from the layout of input tensors
+        # and op type.
         return func(*args, **kwargs)
 
     @property
@@ -85,7 +149,6 @@ class DTensor(torch.Tensor):
         '''
         self.local_tensor = self.local_tensor.to(*args, **kwargs)
         self.data_type = self.local_tensor.dtype
-        self.dist_layout.device_type = self.local_tensor.device
         # TODO: update the device mesh process groups or we should just cache
         # both the cpu process groups and the cuda process groups?
         return self
@@ -98,7 +161,7 @@ class DTensor(torch.Tensor):
 
     def to_global(self):
         '''
-        Recover the global tensor from the distributed tensor.
+        Recover the global tensor from the distributed tensor by returning a new `torch.Tensor` object.
 
         Note: This function will all_gather the local tensor to the global tensor and it
         will not change the layout of the DTensor. This function is mainly used for debugging or
@@ -107,24 +170,29 @@ class DTensor(torch.Tensor):
         return to_global(self.local_tensor, self.dist_layout)
 
 
-def distribute_tensor(local_tensor: torch.Tensor, dist_layout: Layout) -> DTensor:
+def distribute_tensor(tensor: torch.Tensor, device_mesh: DeviceMesh, sharding_spec: ShardingSpec) -> DTensor:
     '''
     Distribute the local tensor to the distributed tensor according to the dist_layout specified.
 
     Args:
-        local_tensor: tensor to be distributed.
-        dist_layout: the layout specification of the distributed tensor.
+        tensor (`torch.Tensor`): tensor to be distributed.
+        device_mesh (`DeviceMesh`): the device mesh for abstraction of the compute devices.
+        sharding_spec (`ShardingSpec`): the sharding specification which describes how the tensor will be sharded.
 
     Returns:
         A 'DTensor' object.
     '''
-    return DTensor(local_tensor, dist_layout)
+    return DTensor(tensor, device_mesh, sharding_spec)
 
 
 def distribute_module(module: torch.nn.Module, partition_fn: Optional[callable] = None) -> torch.nn.Module:
     '''
     This function converts all the parameters in the module to DTensor(DParam).
 
+    Args:
+        module (`torch.nn.Module`): the module to be distributed.
+        partition_fn (callable): the partition function which will be used to partition the parameters.
+
     Note: This function is subject to future change as the DParam has not been implemented yet.
     '''
     for name, param in module.named_parameters():
@@ -138,5 +206,11 @@ def distribute_module(module: torch.nn.Module, partition_fn: Optional[callable]
 def construct_default_sharding_spec(tensor: torch.Tensor,) -> ShardingSpec:
     '''
     Construct the default sharding specification for the tensor.
+
+    Args:
+        tensor (`torch.Tensor`): the tensor to be sharded.
+
+    Returns:
+        A `ShardingSpec` object without any sharding specified.
     '''
     return ShardingSpec(dim_size=tensor.dim(), dim_partition_dict={})

colossalai/tensor/d_tensor/layout.py

@@ -11,28 +11,32 @@ from .sharding_spec import ShardingSpec
 
 
 class Layout:
-    """Layout of a tensor.
+    """
+    Layout of a tensor refers to the tensor placement on the device mesh and how the tensor is sharded over the devices.
 
-    Attributes:
-        device_mesh: the device mesh to store the tensor distributed.
-        device_type: the type of the device mesh, e.g. 'cpu' or 'cuda'.
-        sharding_spec: the sharding specification to describe how the tensor is sharded.
-        entire_shape: the entire shape of the global tensor.
+    Args:
+        device_mesh (`DeviceMesh`): the device mesh to store the tensor distributed.
+        sharding_spec (`ShardingSpec`): the sharding specification to describe how the tensor is sharded.
+        global_shape (`torch.Size`): the entire shape of the global tensor.
     """
 
-    def __init__(self, device_mesh: DeviceMesh, device_type: torch.device, sharding_spec: ShardingSpec,
-                 entire_shape: torch.Size):
+    def __init__(self, device_mesh: DeviceMesh, sharding_spec: ShardingSpec, global_shape: torch.Size):
         self.device_mesh = device_mesh
-        self.device_type = device_type
         self.sharding_spec = sharding_spec
-        self.entire_shape = entire_shape
+        self.global_shape = global_shape
         self._sanity_check()
 
     def __hash__(self) -> int:
         return hash(f'{self.sharding_spec}')
 
-    def get_sharded_shape_per_device(self):
-        sharded_shape = list(self.entire_shape)
+    def get_sharded_shape_per_device(self) -> torch.Size:
+        """
+        Compute the shape of the sharded tensor on each device.
+
+        Returns:
+            `torch.Size`: the shape of the sharded tensor on each device.
+        """
+        sharded_shape = list(self.global_shape)
         for dim, shard_list in self.sharding_spec.dim_partition_dict.items():
             mesh_list = [self.device_mesh.mesh_shape[mesh_dim] for mesh_dim in shard_list]
             shard_partitions = reduce(operator.mul, mesh_list, 1)
@@ -56,7 +60,7 @@ class Layout:
 
         # make sure that the sharding for a dimension is divisible by the number of devices
         for dim, shard_list in sharding_spec.dim_partition_dict.items():
-            tensor_dim_size = self.entire_shape[dim]
+            tensor_dim_size = self.global_shape[dim]
             num_devices = 1
 
             for element in shard_list:

colossalai/tensor/d_tensor/layout_converter.py

@@ -3,10 +3,8 @@ from copy import deepcopy
 from dataclasses import dataclass
 from typing import Dict, List, Tuple
 
-import numpy as np
 import torch
 
-from colossalai.auto_parallel.tensor_shard.sharding_strategy import MemoryCost, TrainCycleItem
 from colossalai.context.singleton_meta import SingletonMeta
 from colossalai.tensor.d_tensor.comm_spec import *
 from colossalai.tensor.d_tensor.layout import Layout
@@ -28,13 +26,21 @@ class LayoutConverterOptions:
     pass
 
 
-def to_global(distributed_tensor: torch.Tensor, layout: Layout) -> torch.Tensor:
+def to_global(distributed_tensor: "DTensor", layout: Layout) -> torch.Tensor:
+    """
+    Convert a distributed tensor to the global tensor with the given layout.
+    This function returns a native `torch.Tensor` object.
+
+
+    Args:
+        distributed_tensor (`DTensor`): the distributed tensor to be converted.
+        layout (`Layout`): the target layout specification.
+    """
     layout_converter = LayoutConverter()
     global_sharding_spec = ShardingSpec(distributed_tensor.dim(), {})
     global_layout = Layout(device_mesh=layout.device_mesh,
-                           device_type=layout.device_type,
                            sharding_spec=global_sharding_spec,
-                           entire_shape=layout.entire_shape)
+                           global_shape=layout.global_shape)
     with torch.no_grad():
         global_tensor = layout_converter.apply(distributed_tensor, layout, global_layout)
     return global_tensor
@@ -49,6 +55,9 @@ def set_layout_converting_options(options: LayoutConverterOptions):
 
 
 class LayoutConverter(metaclass=SingletonMeta):
+    """
+    LayoutConverter is a singleton class which converts the layout of a distributed tensor.
+    """
 
     def __init__(self):
         self._options = None
@@ -91,15 +100,14 @@ class LayoutConverter(metaclass=SingletonMeta):
             # [[0, 1,
             #  [2, 3]]
             device_mesh = DeviceMesh(physical_mesh_id, mesh_shape, init_process_group=True)
-            entire_shape = (4, 4, 4)
+            global_shape = (4, 4, 4)
             dim_partition_dict = {0: [0], 1: [1]}
 
             # [S0,S1,R]
             sharding_spec = ShardingSpec(dim_size=3, dim_partition_dict=dim_partition_dict)
             layout = Layout(device_mesh=device_mesh,
-                            device_type=torch.device('cuda'),
                             sharding_spec=sharding_spec,
-                            entire_shape=entire_shape)
+                            global_shape=global_shape)
 
             rst_dict = layout_converter.all_gather_transform_layouts(layout)
             for layout, comm_spec in rst_dict.items():
@@ -112,7 +120,12 @@ class LayoutConverter(metaclass=SingletonMeta):
         valid_spec_dict = {}
         comm_pattern = CollectiveCommPattern.GATHER_FWD_SPLIT_BWD
         source_spec = source_layout.sharding_spec
-        process_groups_dict = source_layout.device_mesh.process_groups_dict
+
+        # the key of the dict is the axis
+        # the value is the process group
+        current_rank = source_layout.device_mesh._global_rank_of_current_process
+        process_group_dict = source_layout.device_mesh._process_group_dict[current_rank]
+
         for target_pair in source_spec.dim_partition_dict.items():
             shard_list = all_gather_simulator(target_pair)
             index = target_pair[0]
@@ -130,7 +143,7 @@ class LayoutConverter(metaclass=SingletonMeta):
             logical_process_axis = target_pair[1][-1]
             comm_spec = CommSpec(
                 comm_pattern,
-                process_groups_dict=process_groups_dict,
+                process_group_dict=process_group_dict,
                 gather_dim=gather_dim,
             # shard_dim will be used during backward
                 shard_dim=gather_dim,
@@ -141,8 +154,7 @@ class LayoutConverter(metaclass=SingletonMeta):
                 new_sharding_spec = ShardingSpec(source_spec.dims, dim_partition_dict=new_dim_partition_dict)
                 new_layout = Layout(device_mesh=source_layout.device_mesh,
                                     sharding_spec=new_sharding_spec,
-                                    device_type=source_layout.device_type,
-                                    entire_shape=source_layout.entire_shape)
+                                    global_shape=source_layout.global_shape)
 
                 valid_spec_dict[new_layout] = comm_spec
             except LayoutException:
@@ -167,15 +179,14 @@ class LayoutConverter(metaclass=SingletonMeta):
             # [[0, 1,
             #  [2, 3]]
             device_mesh = DeviceMesh(physical_mesh_id, mesh_shape, init_process_group=True)
-            entire_shape = (4, 4, 4)
+            global_shape = (4, 4, 4)
             dim_partition_dict = {0: [0], 1: [1]}
 
             # [S0,S1,R]
             sharding_spec = ShardingSpec(dim_size=3, dim_partition_dict=dim_partition_dict)
             layout = Layout(device_mesh=device_mesh,
-                                    device_type=torch.device('cuda'),
                                     sharding_spec=sharding_spec,
-                                    entire_shape=entire_shape)
+                                    global_shape=global_shape)
             rst_dict = layout_converter.all_to_all_transform_layout(layout)
 
             for layout, comm_spec in rst_dict.items():
@@ -188,7 +199,12 @@ class LayoutConverter(metaclass=SingletonMeta):
         '''
         valid_spec_dict = {}
         comm_pattern = CollectiveCommPattern.ALL2ALL_FWD_ALL2ALL_BWD
-        process_groups_dict = source_layout.device_mesh.process_groups_dict
+
+        # the key of the dict is the axis
+        # the value is the process group
+        current_rank = source_layout.device_mesh._global_rank_of_current_process
+        process_group_dict = source_layout.device_mesh._process_group_dict[current_rank]
+
         source_spec = source_layout.sharding_spec
         tensor_dims = source_spec.dims
         for f_index in range(tensor_dims - 1):
@@ -229,7 +245,7 @@ class LayoutConverter(metaclass=SingletonMeta):
                     shard_dim = f_index
                     logical_process_axis = b_target_pair[1][-1]
                 comm_spec = CommSpec(comm_pattern,
-                                     process_groups_dict,
+                                     process_group_dict=process_group_dict,
                                      gather_dim=gather_dim,
                                      shard_dim=shard_dim,
                                      logical_process_axis=logical_process_axis)
@@ -252,8 +268,7 @@ class LayoutConverter(metaclass=SingletonMeta):
                     new_sharding_spec = ShardingSpec(source_spec.dims, dim_partition_dict=new_dim_partition_dict)
                     new_layout = Layout(device_mesh=source_layout.device_mesh,
                                         sharding_spec=new_sharding_spec,
-                                        device_type=source_layout.device_type,
-                                        entire_shape=source_layout.entire_shape)
+                                        global_shape=source_layout.global_shape)
                     valid_spec_dict[new_layout] = comm_spec
                 except LayoutException:
                     pass
@@ -278,16 +293,15 @@ class LayoutConverter(metaclass=SingletonMeta):
             # [[0, 1,
             #  [2, 3]]
             device_mesh = DeviceMesh(physical_mesh_id, mesh_shape, init_process_group=True)
-            entire_shape = (4, 4, 4)
+            global_shape = (4, 4, 4)
 
             dim_partition_dict = {0: [0]}
 
             # [S0,R,R]
             sharding_spec = ShardingSpec(dim_size=3, dim_partition_dict=dim_partition_dict)
             layout = Layout(device_mesh=device_mesh,
-                          device_type=torch.device('cuda'),
                           sharding_spec=sharding_spec,
-                          entire_shape=entire_shape)
+                          global_shape=global_shape)
             rst_dict = layout_converter.shard_transform_layout(layout)
 
             for layout, comm_spec in rst_dict.items():
@@ -301,7 +315,11 @@ class LayoutConverter(metaclass=SingletonMeta):
         valid_spec_dict = {}
         comm_pattern = CollectiveCommPattern.SPLIT_FWD_GATHER_BWD
         source_spec = source_layout.sharding_spec
-        process_groups_dict = source_layout.device_mesh.process_groups_dict
+
+        # the key of the dict is the axis
+        # the value is the process group
+        current_rank = source_layout.device_mesh._global_rank_of_current_process
+        process_group_dict = source_layout.device_mesh._process_group_dict[current_rank]
 
         # legal sharding dims means the mesh_id is still available to use.
         legal_sharding_dims = [i for i in range(len(source_layout.device_mesh.mesh_shape))]
@@ -329,7 +347,7 @@ class LayoutConverter(metaclass=SingletonMeta):
                 shard_dim = index
                 logical_process_axis = shard_list[-1]
                 comm_spec = CommSpec(comm_pattern,
-                                     process_groups_dict,
+                                     process_group_dict=process_group_dict,
                                      gather_dim=shard_dim,
                                      shard_dim=shard_dim,
                                      logical_process_axis=logical_process_axis)
@@ -340,8 +358,7 @@ class LayoutConverter(metaclass=SingletonMeta):
                                                      dim_partition_dict=new_dim_partition_dict)
                     new_layout = Layout(device_mesh=source_layout.device_mesh,
                                         sharding_spec=new_sharding_spec,
-                                        device_type=source_layout.device_type,
-                                        entire_shape=source_layout.entire_shape)
+                                        global_shape=source_layout.global_shape)
                     valid_spec_dict[new_layout] = comm_spec
                 except LayoutException:
                     pass
@@ -399,7 +416,7 @@ class LayoutConverter(metaclass=SingletonMeta):
             # [[0, 1,
             #  [2, 3]]
             device_mesh = DeviceMesh(physical_mesh_id, mesh_shape, init_process_group=True)
-            entire_shape = (4, 4, 4)
+            global_shape = (4, 4, 4)
 
             dim_partition_source = {1: [0, 1]}
             dim_partition_target = {0: [0, 1]}
@@ -407,16 +424,14 @@ class LayoutConverter(metaclass=SingletonMeta):
             # [R,S01,R]
             sharding_spec_source = ShardingSpec(dim_size=3, dim_partition_dict=dim_partition_source)
             source_layout = Layout(device_mesh=device_mesh,
-                                device_type=torch.device('cuda'),
                                 sharding_spec=sharding_spec_source,
-                                entire_shape=entire_shape)
+                                global_shape=global_shape)
 
             # [S01,R,R]
             sharding_spec_target = ShardingSpec(dim_size=3, dim_partition_dict=dim_partition_target)
             target_layout = Layout(device_mesh=device_mesh,
-                                device_type=torch.device('cuda'),
                                 sharding_spec=sharding_spec_target,
-                                entire_shape=entire_shape)
+                                global_shape=global_shape)
 
             transform_path, comm_action_sequence = layout_converter.layout_converting(source_layout, target_layout)
             transform_path_str = '->'.join([str(layout.sharding_spec.sharding_sequence) for layout in transform_path])
@@ -505,21 +520,19 @@ class LayoutConverter(metaclass=SingletonMeta):
             # [[0, 1,
             #  [2, 3]]
             device_mesh = DeviceMesh(physical_mesh_id, mesh_shape, init_process_group=True)
-            entire_shape = (4, 4, 4)
+            global_shape = (4, 4, 4)
 
             # [S0,R,R]
             sharding_spec_source = ShardingSpec(dim_size=3, dim_partition_dict=dim_partition_source)
             source_layout = Layout(device_mesh=device_mesh,
-                                device_type=torch.device('cuda'),
                                 sharding_spec=sharding_spec_source,
-                                entire_shape=entire_shape)
+                                global_shape=global_shape)
 
             # [R,S0,R]
             sharding_spec_target = ShardingSpec(dim_size=3, dim_partition_dict=dim_partition_target)
             target_layout = Layout(device_mesh=device_mesh,
-                                device_type=torch.device('cuda'),
                                 sharding_spec=sharding_spec_target,
-                                entire_shape=entire_shape)
+                                global_shape=global_shape)
 
             if rank in (0, 1):
                 sharded_tensor_0 = torch.zeros(2, 1)
@@ -554,3 +567,4 @@ class LayoutConverter(metaclass=SingletonMeta):
         for comm_spec in comm_action_sequence:
             tensor = comm_spec.covert_spec_to_action(tensor)
         return tensor
+        return tensor

tests/test_device/test_device_mesh.py

-from colossalai.device.device_mesh import DeviceMesh
 import torch
 
+from colossalai.device.device_mesh import DeviceMesh
+
 
 def test_device_mesh():
-    physical_mesh_id = torch.arange(0, 16).reshape(2, 8)
+    physical_mesh_id = torch.arange(0, 16)
     mesh_shape = (4, 4)
     # [[0, 1, 2, 3],
     #  [4, 5, 6, 7],
     #  [8, 9, 10,11],
     #  [12,13,14,15]]
     device_mesh = DeviceMesh(physical_mesh_id, mesh_shape)
-    assert device_mesh.convert_map[5] == [1, 1]
-    assert device_mesh.convert_map[11] == [2, 3]
-    assert device_mesh.global_rank_to_process_groups_with_logical_rank(0)[0] == [[0, 0], [1, 0], [2, 0], [3, 0]]
-    assert device_mesh.global_rank_to_process_groups_with_logical_rank(2)[1] == [[0, 0], [0, 1], [0, 2], [0, 3]]
-    assert device_mesh.global_rank_to_process_groups_with_global_rank(2)[1] == [0, 1, 2, 3]
+    assert device_mesh.global_rank_to_local_rank(5) == [1, 1]
+    assert device_mesh.global_rank_to_local_rank(11) == [2, 3]
+    assert device_mesh.get_ranks_in_process_group(axis=1, global_rank=2) == [0, 1, 2, 3]
 
 
 if __name__ == '__main__':

tests/test_device/test_init_logical_pg.py

@@ -20,16 +20,12 @@ def check_layer(rank, world_size, port):
     # [[0, 1,
     #  [2, 3]]
     device_mesh = DeviceMesh(physical_mesh_id, mesh_shape, init_process_group=True)
-    logical_pg_dict = {0: [[0, 2], [1, 3]], 1: [[0, 1], [2, 3]]}
-    logical_process_groups = device_mesh.process_groups_dict
-
-    for mesh_dim, pgs in logical_pg_dict.items():
-        for index, pg in enumerate(pgs):
-            if rank in pg:
-                tensor = torch.ones(4).cuda()
-                group = logical_process_groups[mesh_dim][index][1]
-                dist.all_reduce(tensor, op=ReduceOp.SUM, group=group)
-                assert tensor.equal(tensor_to_check)
+
+    for axis in range(len(mesh_shape)):
+        tensor = torch.ones(4).cuda()
+        pg = device_mesh.get_process_group(axis=axis)
+        dist.all_reduce(tensor, op=ReduceOp.SUM, group=pg)
+        assert tensor.equal(tensor_to_check)
 
     gpc.destroy()
 

tests/test_lazy/lazy_init_utils.py

@@ -6,7 +6,9 @@ import numpy as np
 import torch
 from packaging import version
 
+from colossalai.device.device_mesh import DeviceMesh
 from colossalai.lazy.lazy_init import LazyInitContext, LazyTensor, _MyTensor
+from colossalai.tensor.d_tensor.layout import Layout
 from colossalai.tensor.d_tensor.layout_converter import to_global
 from tests.kit.model_zoo.registry import ModelAttribute
 
@@ -81,7 +83,8 @@ def check_lazy_init(entry: TestingEntry, seed: int = 42, verbose: bool = False,
         print(f'{model.__class__.__name__} pass')
 
 
-def assert_dist_model_equal(model: torch.nn.Module, distributed_model: torch.nn.Module, layout_dict: dict) -> None:
+def assert_dist_model_equal(model: torch.nn.Module, distributed_model: torch.nn.Module, device_mesh: DeviceMesh,
+                            sharding_spec_dict: dict) -> None:
     state = model.state_dict()
     distributed_state = distributed_model.state_dict()
 
@@ -91,6 +94,7 @@ def assert_dist_model_equal(model: torch.nn.Module, distributed_model: torch.nn.
         assert n1 == n2
         t1 = t1.cuda()
         t2 = t2.cuda()
-        if n2 in layout_dict:
-            t2 = to_global(t2, layout_dict[n2])
+        if n2 in sharding_spec_dict:
+            layout = Layout(device_mesh=device_mesh, sharding_spec=sharding_spec_dict[n2], global_shape=t1.shape)
+            t2 = to_global(t2, layout)
         assert torch.equal(t1, t2), f'{n1} {t1} vs {t2}'

tests/test_lazy/test_distribute.py

@@ -26,23 +26,19 @@ def find_shard_dim(shape: torch.Size) -> Optional[int]:
             return dim
 
 
-def make_layout(device_mesh: DeviceMesh, original_tensor: torch.Tensor) -> Layout:
+def make_sharding_spec(original_tensor: torch.Tensor) -> Layout:
     shard_dim = find_shard_dim(original_tensor.shape)
     dim_partition_dict = {shard_dim: [0]} if shard_dim is not None else {}
     target_sharding_spec = ShardingSpec(dim_size=original_tensor.dim(), dim_partition_dict=dim_partition_dict)
-    layout = Layout(device_mesh=device_mesh,
-                    device_type=torch.device('cuda'),
-                    sharding_spec=target_sharding_spec,
-                    entire_shape=original_tensor.shape)
-    return layout
+    return target_sharding_spec
 
 
 def _get_current_name(prefix: str, name: str) -> str:
     return f'{prefix}.{name}'.lstrip('.')
 
 
-def generate_layout_dict(model: nn.Module, device_mesh: DeviceMesh) -> dict:
-    layout_dict = {}
+def generate_sharding_spec_dict(model: nn.Module) -> dict:
+    sharding_spec_dict = {}
 
     @torch.no_grad()
     def generate_recursively(module: nn.Module, prefix: str = ''):
@@ -53,17 +49,17 @@ def generate_layout_dict(model: nn.Module, device_mesh: DeviceMesh) -> dict:
         # initialize tensors directly attached to the current module
         for name, param in module.named_parameters(recurse=False):
             if isinstance(param, LazyTensor):
-                layout = make_layout(device_mesh, param)
-                layout_dict[_get_current_name(prefix, name)] = layout
+                sharding_spec = make_sharding_spec(param)
+                sharding_spec_dict[_get_current_name(prefix, name)] = sharding_spec
 
         for name, buf in module.named_buffers(recurse=False):
             if isinstance(buf, LazyTensor):
-                layout = make_layout(device_mesh, buf)
-                layout_dict[_get_current_name(prefix, name)] = layout
+                sharding_spec = make_sharding_spec(buf)
+                sharding_spec_dict[_get_current_name(prefix, name)] = sharding_spec
 
     generate_recursively(model)
 
-    return layout_dict
+    return sharding_spec_dict
 
 
 @parameterize('subset', ['torchvision', 'diffusers', 'timm', 'transformers', 'torchaudio', 'deepfm', 'dlrm'])
@@ -85,9 +81,9 @@ def run_dist_lazy_init(subset, seed: int = 42):
         ctx = LazyInitContext()
         with ctx:
             deferred_model = model_fn()
-        layout_dict = generate_layout_dict(deferred_model, device_mesh)
-        ctx.distribute(deferred_model, layout_dict, verbose=True)
-        assert_dist_model_equal(model, deferred_model, layout_dict)
+        sharding_spec_dict = generate_sharding_spec_dict(deferred_model)
+        ctx.distribute(deferred_model, device_mesh, sharding_spec_dict, verbose=True)
+        assert_dist_model_equal(model, deferred_model, device_mesh, sharding_spec_dict)
 
 
 def run_dist(rank, world_size, port) -> None:

tests/test_tensor/test_dtensor/test_comm_spec.py

@@ -125,23 +125,6 @@ def check_all_reduce_bwd(process_groups_dict, rank):
     assert tensor_to_comm.equal(tensor_to_check)
 
 
-def check_all_reduce_in_flatten_device_mesh(process_groups_dict, rank):
-    # tensor to comm
-    tensor_to_comm = torch.ones(2, 2).cuda() * rank
-
-    # reduce through logical process axis 0 at flatten device mesh
-    # tensor to check
-    # tensor([[6., 6.],
-    #         [6., 6.]])
-    tensor_to_check = torch.tensor([[6, 6], [6, 6]], dtype=tensor_to_comm.dtype).cuda()
-
-    # CommSpec:(comm_pattern:all_reduce, logical_process_axis:[0, 1])
-    comm_spec = CommSpec(CollectiveCommPattern.ALLREDUCE_FWD_IDENTITY_BWD, process_groups_dict, logical_process_axis=0)
-    tensor_to_comm = comm_spec.covert_spec_to_action(tensor_to_comm)
-
-    assert tensor_to_comm.equal(tensor_to_check)
-
-
 def check_comm(rank, world_size, port):
     disable_existing_loggers()
     launch(config={}, rank=rank, world_size=world_size, host='localhost', port=port, backend='nccl')
@@ -153,24 +136,22 @@ def check_comm(rank, world_size, port):
     # [[0, 1,
     #  [2, 3]]
     device_mesh = DeviceMesh(physical_mesh_id, mesh_shape, init_process_group=True)
-    process_groups_dict = device_mesh.process_groups_dict
+
+    process_group_dict = device_mesh._process_group_dict[rank]
 
     # test all gather
-    check_all_gather(process_groups_dict, rank)
+    check_all_gather(process_group_dict, rank)
 
     # test shard
-    check_shard(process_groups_dict, rank)
+    check_shard(process_group_dict, rank)
 
     # test all to all
-    check_all_to_all(process_groups_dict, rank)
+    check_all_to_all(process_group_dict, rank)
 
     # test all reduce
-    check_all_reduce_fwd(process_groups_dict, rank)
-    check_all_reduce_bwd(process_groups_dict, rank)
+    check_all_reduce_fwd(process_group_dict, rank)
+    check_all_reduce_bwd(process_group_dict, rank)
 
-    flatten_process_groups_dict = device_mesh.flatten_device_mesh.process_groups_dict
-    # test all reduce in 1D flatten device mesh
-    check_all_reduce_in_flatten_device_mesh(flatten_process_groups_dict, rank)
     gpc.destroy()
 
 

tests/test_tensor/test_dtensor/test_dtensor.py

@@ -31,13 +31,9 @@ def check_dtensor(rank, world_size, port):
 
     device_mesh = DeviceMesh(torch.Tensor([0, 1, 2, 3]), (2, 2), init_process_group=True)
     target_sharding_spec = ShardingSpec(dim_size=original_tensor.dim(), dim_partition_dict={0: [0]})
-    layout = Layout(device_mesh=device_mesh,
-                    device_type=torch.device('cuda'),
-                    sharding_spec=target_sharding_spec,
-                    entire_shape=original_tensor.shape)
-    d_tensor = DTensor(original_tensor, layout)
+    d_tensor = DTensor(original_tensor, device_mesh, target_sharding_spec)
 
-    assert d_tensor.entire_shape == original_tensor.shape
+    assert d_tensor.global_shape == original_tensor.shape
     assert d_tensor.data_type == original_tensor.dtype
 
     if rank in (0, 1):
@@ -57,12 +53,7 @@ def check_dtensor(rank, world_size, port):
         raise ValueError(f'rank {rank} is not in the device mesh')
 
     new_sharding_spec = ShardingSpec(dim_size=original_tensor.dim(), dim_partition_dict={0: [0, 1]})
-    new_layout = Layout(device_mesh=device_mesh,
-                        device_type=torch.device('cuda'),
-                        sharding_spec=new_sharding_spec,
-                        entire_shape=original_tensor.shape)
-
-    d_tensor.layout_convert(new_layout)
+    d_tensor.layout_convert(device_mesh, new_sharding_spec)
 
     if rank == 0:
         assert d_tensor.local_tensor.equal(original_tensor.narrow(0, 0, 1))
@@ -75,7 +66,7 @@ def check_dtensor(rank, world_size, port):
     else:
         raise ValueError(f'rank {rank} is not in the device mesh')
 
-    dtensor_from_local = distribute_tensor(original_tensor, new_layout)
+    dtensor_from_local = distribute_tensor(original_tensor, device_mesh, new_sharding_spec)
 
     if rank == 0:
         assert dtensor_from_local.local_tensor.equal(original_tensor.narrow(0, 0, 1))

tests/test_tensor/test_dtensor/test_layout_converter.py

@@ -12,9 +12,9 @@ from colossalai.tensor.d_tensor.layout_converter import LayoutConverter
 from colossalai.tensor.d_tensor.sharding_spec import DimSpec, ShardingSpec
 from colossalai.testing import rerun_if_address_is_in_use, spawn
 
-entire_shape = torch.Size((64, 32, 16))
+global_shape = torch.Size((64, 32, 16))
 layout_converter = LayoutConverter()
-physical_mesh_id = torch.arange(0, 4).reshape(2, 2)
+physical_mesh_id = torch.arange(0, 4)
 mesh_shape = (2, 2)
 
 
@@ -30,10 +30,7 @@ def check_one_step_transform(rank, world_size, port):
     #     shard_sequence: S0,S1,R
     #     device_mesh_shape: (2, 2)
     sharding_spec = ShardingSpec(dim_size=3, dim_partition_dict=dim_partition_dict)
-    layout = Layout(device_mesh=device_mesh,
-                    device_type=torch.device('cuda'),
-                    sharding_spec=sharding_spec,
-                    entire_shape=entire_shape)
+    layout = Layout(device_mesh=device_mesh, sharding_spec=sharding_spec, global_shape=global_shape)
 
     rst_dict = layout_converter.all_gather_transform_layouts(layout)
 
@@ -49,10 +46,7 @@ def check_one_step_transform(rank, world_size, port):
     #     shard_sequence: S0,S1,R
     #     device_mesh_shape: (4, 4)
     sharding_spec_all2all = ShardingSpec(dim_size=3, dim_partition_dict=dim_partition_dict_all2all)
-    layout_all2all = Layout(device_mesh=device_mesh,
-                            device_type=torch.device('cuda'),
-                            sharding_spec=sharding_spec_all2all,
-                            entire_shape=entire_shape)
+    layout_all2all = Layout(device_mesh=device_mesh, sharding_spec=sharding_spec_all2all, global_shape=global_shape)
 
     rst_dict_all2all = layout_converter.all_to_all_transform_layout(layout_all2all)
 
@@ -71,10 +65,7 @@ def check_one_step_transform(rank, world_size, port):
     #     shard_sequence: S0,R,R
     #     device_mesh_shape: (4, 4)
     sharding_spec_shard = ShardingSpec(dim_size=3, dim_partition_dict=dim_partition_shard)
-    shard_layout = Layout(device_mesh=device_mesh,
-                          device_type=torch.device('cuda'),
-                          sharding_spec=sharding_spec_shard,
-                          entire_shape=entire_shape)
+    shard_layout = Layout(device_mesh=device_mesh, sharding_spec=sharding_spec_shard, global_shape=global_shape)
 
     rst_dict_shard = layout_converter.shard_transform_layout(shard_layout)
 
@@ -100,19 +91,13 @@ def check_layout_converting(rank, world_size, port):
     #     shard_sequence: R,S01,R
     #     device_mesh_shape: (4, 4)
     sharding_spec_source = ShardingSpec(dim_size=3, dim_partition_dict=dim_partition_source)
-    source_layout = Layout(device_mesh=device_mesh,
-                           device_type=torch.device('cuda'),
-                           sharding_spec=sharding_spec_source,
-                           entire_shape=entire_shape)
+    source_layout = Layout(device_mesh=device_mesh, sharding_spec=sharding_spec_source, global_shape=global_shape)
 
     # DistSpec:
     #     shard_sequence: S01,R,R
     #     device_mesh_shape: (4, 4)
     sharding_spec_target = ShardingSpec(dim_size=3, dim_partition_dict=dim_partition_target)
-    target_layout = Layout(device_mesh=device_mesh,
-                           device_type=torch.device('cuda'),
-                           sharding_spec=sharding_spec_target,
-                           entire_shape=entire_shape)
+    target_layout = Layout(device_mesh=device_mesh, sharding_spec=sharding_spec_target, global_shape=global_shape)
 
     transform_path, comm_action_sequence = layout_converter.layout_converting(source_layout, target_layout)
 
@@ -159,21 +144,15 @@ def check_layout_converting_apply(rank, world_size, port):
     #     shard_sequence: R,S01,R
     #     device_mesh_shape: (4, 4)
     sharding_spec_source = ShardingSpec(dim_size=3, dim_partition_dict=dim_partition_source)
-    source_layout = Layout(device_mesh=device_mesh,
-                           device_type=torch.device('cuda'),
-                           sharding_spec=sharding_spec_source,
-                           entire_shape=entire_shape)
+    source_layout = Layout(device_mesh=device_mesh, sharding_spec=sharding_spec_source, global_shape=global_shape)
 
     # DistSpec:
     #     shard_sequence: S01,R,R
     #     device_mesh_shape: (4, 4)
     sharding_spec_target = ShardingSpec(dim_size=3, dim_partition_dict=dim_partition_target)
-    target_layout = Layout(device_mesh=device_mesh,
-                           device_type=torch.device('cuda'),
-                           sharding_spec=sharding_spec_target,
-                           entire_shape=entire_shape)
+    target_layout = Layout(device_mesh=device_mesh, sharding_spec=sharding_spec_target, global_shape=global_shape)
 
-    original_tensor = torch.rand(entire_shape).cuda()
+    original_tensor = torch.rand(global_shape).cuda()
 
     # tensor_to_apply: [R, S01, R]
     tensor_to_apply = original_tensor.narrow(1, rank * 8, 8)

tests/test_tensor/test_shape_consistency.py

-from colossalai.tensor.shape_consistency import ShapeConsistencyManager, CollectiveCommPattern
 import torch
-from colossalai.tensor.sharding_spec import _DimSpec, ShardingSpec
+
 from colossalai.device.device_mesh import DeviceMesh
+from colossalai.tensor.shape_consistency import CollectiveCommPattern, ShapeConsistencyManager
+from colossalai.tensor.sharding_spec import ShardingSpec, _DimSpec
 
-physical_mesh_id = torch.arange(0, 16).reshape(2, 8)
+physical_mesh_id = torch.arange(0, 16)
 mesh_shape = (4, 4)
 # [[0, 1, 2, 3],
 #  [4, 5, 6, 7],

tests/test_tensor/test_sharded_linear.py

@@ -26,7 +26,7 @@ def run_dist(rank, world_size, port):
     # the mesh is in the following topo
     # [[0, 1],
     #  [2, 3]]
-    physical_mesh_id = torch.arange(0, 4).reshape(2, 2)
+    physical_mesh_id = torch.arange(0, 4)
     mesh_shape = (2, 2)
     device_mesh = DeviceMesh(physical_mesh_id, mesh_shape)
     row_id = rank // 2

tests/test_tensor/test_sharding_spec.py

@@ -5,7 +5,7 @@ from colossalai.tensor.sharding_spec import ShardingSpec, _DimSpec
 
 
 def test_sharding_spec():
-    physical_mesh_id = torch.arange(0, 16).reshape(2, 8)
+    physical_mesh_id = torch.arange(0, 16)
     mesh_shape = (4, 4)
     # [[0, 1, 2, 3],
     #  [4, 5, 6, 7],