[Docs] Add docs about how to set the random seed (#386)

* how to set seed

* minor fix

docs/en/advanced_guides/how_to.md

@@ -463,3 +463,22 @@ mim run mmdet print_config \
 ```
 
 Running the above command will save the `yolov5_s-v61_syncbn_fast_1xb4-300e_balloon.py` config file with the inheritance relationship expanded to \`\`yolov5_s-v61_syncbn_fast_1xb4-300e_balloon_whole.py`in the`./work_dirs\` folder.
+
+## Set the random seed
+
+If you want to set the random seed during training, you can use the following command.
+
+```shell
+python ./tools/train.py \
+    ${CONFIG} \                               # path of the config file
+    --cfg-options randomness.seed=2023 \      # set seed to 2023
+    [randomness.diff_rank_seed=True] \        # set different seeds according to global rank
+    [randomness.deterministic=True]           # set the deterministic option for CUDNN backend
+# [] stands for optional parameters, when actually entering the command line, you do not need to enter []
+```
+
+`randomness` has three parameters that can be set, with the following meanings.
+
+- `randomness.seed=2023`, set the random seed to 2023.
+- `randomness.diff_rank_seed=True`, set different seeds according to global rank. Defaults to False.
+- `randomness.deterministic=True`, set the deterministic option for cuDNN backend, i.e., set `torch.backends.cudnn.deterministic` to True and `torch.backends.cudnn.benchmark` to False. Defaults to False. See https://pytorch.org/docs/stable/notes/randomness.html for more details.

docs/zh_cn/advanced_guides/how_to.md

@@ -466,3 +466,24 @@ mim run mmdet print_config \
 ```
 
 运行以上命令，会将 `yolov5_s-v61_syncbn_fast_1xb4-300e_balloon.py` 继承关系展开后的配置文件保存到 `./work_dirs` 文件夹内的 `yolov5_s-v61_syncbn_fast_1xb4-300e_balloon_whole.py` 文件中。
+
+## 设置随机种子
+
+如果想要在训练时指定随机种子，可以使用以下命令：
+
+```shell
+python ./tools/train.py \
+    ${CONFIG} \                               # 配置文件路径
+    --cfg-options randomness.seed=2023 \      # 设置随机种子为 2023
+    [randomness.diff_rank_seed=True] \        # 根据 rank 来设置不同的种子。
+    [randomness.deterministic=True]           # 把 cuDNN 后端确定性选项设置为 True
+# [] 代表可选参数，实际输入命令行时，不用输入 []
+```
+
+`randomness` 有三个参数可设置，具体含义如下：
+
+- `randomness.seed=2023` ，设置随机种子为 2023。
+
+- `randomness.diff_rank_seed=True`，根据 rank 来设置不同的种子，`diff_rank_seed` 默认为 False。
+
+- `randomness.deterministic=True`，把 cuDNN 后端确定性选项设置为 True，即把`torch.backends.cudnn.deterministic` 设为 True，把 `torch.backends.cudnn.benchmark` 设为False。`deterministic` 默认为 False。更多细节见 https://pytorch.org/docs/stable/notes/randomness.html。