[Docs] Add model docs. (#11)

* [Docs] Add model docs.

* Imporve according to comments

docs/en/user_guides/models.md

 # Prepare Models
+
+To support the evaluation of new models in OpenCompass, there are several ways:
+
+1. HuggingFace-based models
+2. API-based models
+3. Custom models
+
+## HuggingFace-based Models
+
+In OpenCompass, we support constructing evaluation models directly from HuggingFace's
+`AutoModel.from_pretrained` and `AutoModelForCausalLM.from_pretrained` interfaces. If the model to be
+evaluated follows the typical generation interface of HuggingFace models, there is no need to write code. You
+can simply specify the relevant configurations in the configuration file.
+
+Here is an example configuration file for a HuggingFace-based model:
+
+```python
+# Use `HuggingFace` to evaluate models supported by AutoModel.
+# Use `HuggingFaceCausalLM` to evaluate models supported by AutoModelForCausalLM.
+from opencompass.models import HuggingFaceCausalLM
+
+models = [
+    dict(
+        type=HuggingFaceCausalLM,
+        # Parameters for `HuggingFaceCausalLM` initialization.
+        path='huggyllama/llama-7b',
+        tokenizer_path='huggyllama/llama-7b',
+        tokenizer_kwargs=dict(padding_side='left', truncation_side='left'),
+        max_seq_len=2048,
+        batch_padding=False,
+        # Common parameters shared by various models, not specific to `HuggingFaceCausalLM` initialization.
+        abbr='llama-7b',            # Model abbreviation used for result display.
+        max_out_len=100,            # Maximum number of generated tokens.
+        batch_size=16,              # The size of a batch during inference.
+        run_cfg=dict(num_gpus=1),   # Run configuration to specify resource requirements.
+    )
+]
+```
+
+Explanation of some of the parameters:
+
+- `batch_padding=False`: If set to False, each sample in a batch will be inferred individually. If set to True,
+  a batch of samples will be padded and inferred together. For some models, such padding may lead to
+  unexpected results. If the model being evaluated supports sample padding, you can set this parameter to True
+  to speed up inference.
+- `padding_side='left'`: Perform padding on the left side. Not all models support padding, and padding on the
+  right side may interfere with the model's output.
+- `truncation_side='left'`: Perform truncation on the left side. The input prompt for evaluation usually
+  consists of both the in-context examples prompt and the input prompt. If the right side of the input prompt
+  is truncated, it may cause the input of the generation model to be inconsistent with the expected format.
+  Therefore, if necessary, truncation should be performed on the left side.
+
+During evaluation, OpenCompass will instantiate the evaluation model based on the `type` and the
+initialization parameters specified in the configuration file. Other parameters are used for inference,
+summarization, and other processes related to the model. For example, in the above configuration file, we will
+instantiate the model as follows during evaluation:
+
+```python
+model = HuggingFaceCausalLM(
+    path='huggyllama/llama-7b',
+    tokenizer_path='huggyllama/llama-7b',
+    tokenizer_kwargs=dict(padding_side='left', truncation_side='left'),
+    max_seq_len=2048,
+)
+```
+
+## API-based Models
+
+Currently, OpenCompass supports API-based model inference for the following:
+
+- OpenAI (`opencompass.models.OpenAI`)
+- More coming soon
+
+Let's take the OpenAI configuration file as an example to see how API-based models are used in the
+configuration file.
+
+```python
+from opencompass.models import OpenAI
+
+models = [
+    dict(
+        type=OpenAI,                             # Using the OpenAI model
+        # Parameters for `OpenAI` initialization
+        path='gpt-4',                            # Specify the model type
+        key='YOUR_OPENAI_KEY',                   # OpenAI API Key
+        max_seq_len=2048,                        # The max input number of tokens
+        # Common parameters shared by various models, not specific to `OpenAI` initialization.
+        abbr='GPT-4',                            # Model abbreviation used for result display.
+        max_out_len=512,                         # Maximum number of generated tokens.
+        batch_size=1,                            # The size of a batch during inference.
+        run_cfg=dict(num_gpus=0),                # Resource requirements (no GPU needed)
+    ),
+]
+```
+
+# Custom Models
+
+If the above methods do not support your model evaluation requirements, you can refer to
+[Supporting New Models](../advanced_guides/new_model.md) to add support for new models in OpenCompass.

docs/zh_cn/user_guides/models.md

 # 准备模型
+
+要在 OpenCompass 中支持新模型的评测，有以下几种方式：
+
+1. 基于 HuggingFace 的模型
+2. 基于 API 的模型
+3. 自定义模型
+
+## 基于 HuggingFace 的模型
+
+在 OpenCompass 中，我们支持直接从 Huggingface 的 `AutoModel.from_pretrained` 和
+`AutoModelForCausalLM.from_pretrained` 接口构建评测模型。如果需要评测的模型符合 HuggingFace 模型通常的生成接口，
+则不需要编写代码，直接在配置文件中指定相关配置即可。
+
+如下，为一个示例的 HuggingFace 模型配置文件：
+
+```python
+# 使用 `HuggingFace` 评测 HuggingFace 中 AutoModel 支持的模型
+# 使用 `HuggingFaceCausalLM` 评测 HuggingFace 中 AutoModelForCausalLM 支持的模型
+from opencompass.models import HuggingFaceCausalLM
+
+models = [
+    dict(
+        type=HuggingFaceCausalLM,
+        # 以下参数为 `HuggingFaceCausalLM` 的初始化参数
+        path='huggyllama/llama-7b',
+        tokenizer_path='huggyllama/llama-7b',
+        tokenizer_kwargs=dict(padding_side='left', truncation_side='left'),
+        max_seq_len=2048,
+        batch_padding=False,
+        # 以下参数为各类模型都有的参数，非 `HuggingFaceCausalLM` 的初始化参数
+        abbr='llama-7b',            # 模型简称，用于结果展示
+        max_out_len=100,            # 最长生成 token 数
+        batch_size=16,              # 批次大小
+        run_cfg=dict(num_gpus=1),   # 运行配置，用于指定资源需求
+    )
+]
+```
+
+对以上一些参数的说明：
+
+- `batch_padding=False`：如为 False，会对一个批次的样本进行逐一推理；如为 True，则会对一个批次的样本进行填充，
+  组成一个 batch 进行推理。对于部分模型，这样的填充可能导致意料之外的结果；如果评测的模型支持样本填充，
+  则可以将该参数设为 True，以加速推理。
+- `padding_side='left'`：在左侧进行填充，因为不是所有模型都支持填充，在右侧进行填充可能会干扰模型的输出。
+- `truncation_side='left'`：在左侧进行截断，评测输入的 prompt 通常包括上下文样本 prompt 和输入 prompt 两部分，
+  如果截断右侧的输入 prompt，可能导致生成模型的输入和预期格式不符，因此如有必要，应对左侧进行截断。
+
+在评测时，OpenCompass 会使用配置文件中的 `type` 与各个初始化参数实例化用于评测的模型，
+其他参数则用于推理及总结等过程中，与模型相关的配置。例如上述配置文件，我们会在评测时进行如下实例化过程：
+
+```python
+model = HuggingFaceCausalLM(
+    path='huggyllama/llama-7b',
+    tokenizer_path='huggyllama/llama-7b',
+    tokenizer_kwargs=dict(padding_side='left', truncation_side='left'),
+    max_seq_len=2048,
+)
+```
+
+# 基于 API 的模型
+
+OpenCompass 目前支持以下基于 API 的模型推理：
+
+- OpenAI（`opencompass.models.OpenAI`）
+- Coming soon
+
+以下，我们以 OpenAI 的配置文件为例，模型如何在配置文件中使用基于 API 的模型。
+
+```python
+from opencompass.models import OpenAI
+
+models = [
+    dict(
+        type=OpenAI,                             # 使用 OpenAI 模型
+        # 以下为 `OpenAI` 初始化参数
+        path='gpt-4',                            # 指定模型类型
+        key='YOUR_OPENAI_KEY',                   # OpenAI API Key
+        max_seq_len=2048,                        # 最大输入长度
+        # 以下参数为各类模型都有的参数，非 `OpenAI` 的初始化参数
+        abbr='GPT-4',                            # 模型简称
+        run_cfg=dict(num_gpus=0),                # 资源需求（不需要 GPU）
+        max_out_len=512,                         # 最长生成长度
+        batch_size=1,                            # 批次大小
+    ),
+]
+```
+
+# 自定义模型
+
+如果以上方式无法支持你的模型评测需求，请参考 [支持新模型](../advanced_guides/new_model.md) 在 OpenCompass 中增添新的模型支持。