chatgpt的预训练模型Transformer的源代码

ChatGPT使用了OpenAI公司开源的GPT-2模型，该模型基于Transformer架构，其源代码可以在GitHub上获取。以下是GPT-2的Transformer部分的源代码片段：

class Block(nn.Module):
    def __init__(self, n_ctx, config, scale=False):
        super(Block, self).__init__()
        nx = config.n_embd
        self.ln_1 = LayerNorm(nx, eps=config.layer_norm_epsilon)
        self.attn = Attention(nx, n_ctx, config, scale)
        self.ln_2 = LayerNorm(nx, eps=config.layer_norm_epsilon)
        self.mlp = MLP(4 * nx, config)
        self.dropout1 = nn.Dropout(config.dropout)
        self.dropout2 = nn.Dropout(config.dropout)

    def forward(self, x, layer_past=None):
        a = self.ln_1(x)
        output_attn = self.attn(a, layer_past=layer_past)
        x = x + self.dropout1(output_attn)
        m = self.ln_2(x)
        m = self.mlp(m)
        x = x + self.dropout2(m)
        return x, output_attn

这里的`Block`类表示GPT-2模型的一个Transformer block，其中包含了LayerNorm、Attention、MLP和Dropout等模块。`Attention`和`MLP`是Transformer中的核心模块，分别用于计算self-attention和feed-forward层。