[doc] add shardformer support matrix/update tensor parallel documents (#4728)

* add compatibility matrix for shardformer doc

* update tp doc
This commit is contained in:
Baizhou Zhang
2023-09-15 13:52:30 +08:00
committed by GitHub
parent 8c2dda7410
commit 50e5602c2d
10 changed files with 374 additions and 728 deletions

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@@ -60,83 +60,9 @@ Given $P=q\times q$ processors, we present the theoretical computation and memor
## Usage
To enable 2D tensor parallelism for our model, e.g. on 4 GPUs, we need to configure the parallelism setting as below.
```python
CONFIG = dict(parallel=dict(
data=1,
pipeline=1,
tensor=dict(size=4, mode='2d'),
))
```
Then Colossal-AI will automatically apply 2D parallelism to all the layers from `colossalai.nn`.
Currently the newest version of ColossalAI doesn't support 2D tensor parallelism, but this feature will be integrated into `Shardformer` in future releases.
For more details about ideas and usages of `Shardformer`, please refer to [Shardformer Doc](./shardformer.md).
Let's define a model that consists of a two-layer multi-layer perceptron (MLP) as below.
```python
import colossalai
import colossalai.nn as col_nn
import torch
from colossalai.utils import print_rank_0
For users of older version of ColossalAI, please refer to [ColossalAI-Examples - 2D Tensor Parallelism](https://github.com/hpcaitech/ColossalAI-Examples/blob/main/features/tensor_parallel/README.md).
class MLP(torch.nn.Module):
def __init__(self, dim: int = 256):
super().__init__()
intermediate_dim = dim * 4
self.dense_1 = col_nn.Linear(dim, intermediate_dim)
print_rank_0(f'Weight of the first linear layer: {self.dense_1.weight.shape}')
self.activation = torch.nn.GELU()
self.dense_2 = col_nn.Linear(intermediate_dim, dim)
print_rank_0(f'Weight of the second linear layer: {self.dense_2.weight.shape}')
self.dropout = col_nn.Dropout(0.1)
def forward(self, x):
x = self.dense_1(x)
print_rank_0(f'Output of the first linear layer: {x.shape}')
x = self.activation(x)
x = self.dense_2(x)
print_rank_0(f'Output of the second linear layer: {x.shape}')
x = self.dropout(x)
return x
```
Launch Colossal-AI on 4 GPUs and build the model
```python
parser = colossalai.get_default_parser()
colossalai.launch(config=CONFIG,
rank=args.rank,
world_size=args.world_size,
local_rank=args.local_rank,
host=args.host,
port=args.port)
m = MLP()
```
We will see the shapes of partitioned parameters(e.g. weights) in the MLP model.
```shell
Weight of the first linear layer: torch.Size([128, 512])
Weight of the second linear layer: torch.Size([512, 128])
```
The complete weight of the first linear layer is supposed to have the shape `[256, 1024]`. After the partitioning of 2D parallelism, it becomes `[128, 512]` on each GPU.
Similarly, the second layer partitions the weight `[1024, 256]` into `[512, 128]`.
We can run the model with some random inputs.
```python
from colossalai.context import ParallelMode
from colossalai.core import global_context as gpc
from colossalai.utils import get_current_device
x = torch.randn((16, 256), device=get_current_device())
# partition input
torch.distributed.broadcast(x, src=0)
x = torch.chunk(x, 2, dim=0)[gpc.get_local_rank(ParallelMode.PARALLEL_2D_COL)]
x = torch.chunk(x, 2, dim=-1)[gpc.get_local_rank(ParallelMode.PARALLEL_2D_ROW)]
print_rank_0(f'Input: {x.shape}')
x = m(x)
```
Then we can see the shapes of activation results.
```shell
Input: torch.Size([8, 128])
Output of the first linear layer: torch.Size([8, 512])
Output of the second linear layer: torch.Size([8, 128])
```
The activation tensors in 2D parallelism are all split in both row and column.
E.g. the output of the first linear layer has the shape `[8, 512]`, while the second layer has the output of `[8, 128]`.
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