[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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@@ -60,82 +60,8 @@ $$
## 使用
为了使我们的模型能够实现二维张量并行例如在4个 GPU 上,我们需要配置如下的并行设置
```python
CONFIG = dict(parallel=dict(
data=1,
pipeline=1,
tensor=dict(size=4, mode='2d'),
))
```
然后 Colossal-AI 会自动对所有来自 `colossalai.nn` 的层应用2D张量并行。
ColossalAI的最新版本还暂不支持2D张量并行但2D张量并行的功能会在未来的版本被集成入`Shardformer`中。关于`Shardformer`的原理和用法细节请参考当前目录下的Shardformer文档
让我们定义一个由两层多层感知器 (MLP) 组成的模型,如下所示
```python
import colossalai
import colossalai.nn as col_nn
import torch
from colossalai.utils import print_rank_0
对于老版本ColossalAI的用户2D张量并行的用法请参考[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
```
在4个 GPU 上启动 Colossal-AI 并建立模型。
```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()
```
我们将会看到 MLP 模型中被划分的参数(如权重)的形状。
```shell
Weight of the first linear layer: torch.Size([128, 512])
Weight of the second linear layer: torch.Size([512, 128])
```
第一个线性层的完整权重形状应该为 `[256, 1024]`. 经过2D并行划分后它在每个 GPU 上变成了 `[128, 512]`
同样地,第二层将权重 `[1024, 256]` 划分为 `[512, 128]`.
我们可以用一些随机输入来运行这个模型。
```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)
```
然后我们可以看到 activation 结果的形状。
```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])
```
2D并行中的 activation 张量都是同时在行和列分割的。例如,第一个线性层的输出是 `[8, 512]`, 而第二层的输出为 `[8, 128]`
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