大模型入门1: 指令微调

1. scaling law
2. 大模型评测
3. 指令微调

微调7B模型需要3×28G的显存(SGD+Momentum)，至少需要2张A100的显卡才能满足

数据

格式

wget https://raw.githubusercontent.com/baichuan-inc/Baichuan2/main/fine-tune/data/belle_chat_ramdon_10k.json
wget https://huggingface.co/datasets/BelleGroup/school_math_0.25M/resolve/main/school_math_0.25M.json

import json

data_path = "/root/autodl-tmp/belle_chat_ramdon_10k.json"
x = json.load(open(data_path))
print(x[0])
print(x[1])

{‘id’: ‘77771’, ‘conversations’: [{‘from’: ‘human’, ‘value’: ‘写一篇关于气候变化对海洋生态的影响的文章。\n’}, {‘from’: ‘gpt’, ‘value’: ‘好的，以下是你要求的文章：\n气候变化对海洋生态的影响\n气候变化对海洋生态产生了广泛的影响。全球变暖导致海洋温度上升，这可能会对许多水生生物的生存、繁殖和迁移造成巨大的影响。另外，海洋酸化也是一个问题，因为大气中二氧化碳的增加导致海水中的pH值下降，使得许多生物的外骨骼变得脆弱，从而影响它们的生存和繁殖。\n此外，气候变化还会引起海平面上升，这不仅对海岸线和沿海居民产生影响，还会对许多海洋生物的栖息地造成影响。一些岛屿上的陆地生物面临几乎完全消失的风险，而另一些生物范围则会扩大到更广泛的领域，这可能会导致新的竞争和生态平衡的改变。\n总之，气候变化并不只是一个地球气温的问题，它对海洋生态系统产生了广泛和深远的影响。\n’}, {‘from’: ‘human’, ‘value’: ‘从刚刚的文章中提取出气候变化对海洋生物繁殖的影响。\n’}, {‘from’: ‘gpt’, ‘value’: ‘文章已经提到过气候变化会对海洋生物的生存、繁殖和迁移造成影响。例如，海洋酸化会使得许多生物的外骨骼变得脆弱，进而影响它们的生存和繁殖。此外，海洋温度上升也可能会对很多生物的生存和繁殖产生负面影响。’}]}

{‘id’: ‘27684’, ‘conversations’: [{‘from’: ‘human’, ‘value’: ‘你好，请问你能帮我查一下明天的天气吗？\n’}, {‘from’: ‘gpt’, ‘value’: ‘当然，你在哪个城市呢？\n’}, {‘from’: ‘human’, ‘value’: ‘我在上海。\n’}, {‘from’: ‘gpt’, ‘value’: ‘好的，根据天气预报，明天上海多云转阴，气温在20到25摄氏度之间。需要我帮你查询其他信息吗？’}]}

也就是每一条id, 和 conversations. 然后conversations中分别是多个from value的组合

f_write = open("/root/autodl-tmp/school_math_0.25M_conv.json", "w")
data_path = "/root/autodl-tmp/school_math_0.25M.json"

with open(data_path) as f:
    lines = f.readlines()
    num_id = 1
    for line in lines:
        data = json.loads(line)
        print(data)
        # conversations = [{"from": "human", "value": data['instruction']+data['input']},{"from": "assistant", "value": data['output']}]
        # # conversations = [{"from": "human", "value": data['input']},{"from": "assistant", "value": data['target']}]
        # uniq_id = data['id'] if "id" in data else args.dataset_name+"-"+str(num_id)
        # item = {"id":uniq_id, "conversations": conversations}
        # f_write.write(json.dumps(item, ensure_ascii=False)+"\n")
        num_id += 1
        if num_id > 3:
            break
f_write.close()

{‘instruction’: ‘题目：小明每天早上花费10分钟时间走到学校，如果小明家距离学校2公里，那么他每分钟走多少米？’, ‘input’: ‘’, ‘output’: ‘这是一个关于速度、路程、时间的数学问题。我们可以通过公式：速度＝路程÷时间 来解决。\n因为小明每天早上走2公里，所以他的路程为2千米。而他每天早上要花费10分钟时间走到学校，因此他的时间为10分钟，即600秒。\n所以小明每分钟走的距离为 2公里 / 600秒 = 0.0033公里/秒 或 3.3米/秒。\n答案：小明每分钟走3.3米。’}

{‘instruction’: ‘题目：今天小明骑自行车从家到学校用了20分钟，回家用了25分钟。如果小明在上学和回家的路上的速度一样，那么他从家到学校的距离是学校到家的距离的百分之几？’, ‘input’: ‘’, ‘output’: ‘\n假设小明家到学校的距离为x千米，根据速度等于路程除以时间的公式，可以得出小明的速度为：家到学校的速度 = x / 20，学校到家的速度 = x / 25。因为小明在上学和回家的路上的速度一样，所以有：x / 20 = x / 25，解出 x = 5/4 千米。\n因此，家到学校的距离是学校到家的距离的百分之几，可以通过求比值得到：x / (5/4)x = 4/5 = 0.8，即小明从家到学校的距离是学校到家的距离的百分之80。’}

{‘instruction’: ‘题目：\n鹿妈妈买了24个苹果，她想平均分给她的3只小鹿吃，每只小鹿可以分到几个苹果？’, ‘input’: ‘’, ‘output’: ‘\n鹿妈妈买了24个苹果，平均分给3只小鹿吃，那么每只小鹿可以分到的苹果数就是总苹果数除以小鹿的只数。\n24÷3=8\n每只小鹿可以分到8个苹果。所以，答案是每只小鹿可以分到8个苹果。’}

每一条包括instruction, input, output三个item
其中注释的代码，可以将格式转化为与上面相同

LoRA

低秩适配器

• 图像中可以理解为某种图像风格的适配器
• 本质上是因为大模型的过参数化，认为有某个更小的维度（内部维度，intrinsic dimension）可以足够表征任务，类似找到真正的抽象核心去调整. 对于预训练权重矩阵，我们可以用一个低秩分解来表示参数更新
• 训练参数仅为整体参数的万分之一、GPU显存使用量减少2/3且不会引入额外的推理耗时

实现

• 原模型旁边增加一个旁路，通过低秩分解（先降维再升维）来模拟参数的更新量
• 训练时，原模型固定，只训练降维矩阵A和升维矩阵B. 由于不需要对模型的权重参数重新计算梯度，大大减少了需要训练的计算量。
• 推理时，可将BA加到原参数上，不引入额外的推理延迟
• 初始化，A采用高斯分布初始化，B初始化为全0，保证训练开始时旁路为0矩阵
• 可插拔式的切换任务，当前任务W0+B1A1，将lora部分减掉，换成B2A2，即可实现任务切换；
• 秩的选取：对于一般的任务，rank=1,2,4,8足矣，而对于一些领域差距比较大的任务可能需要更大的rank。

代码

• 将可微调参数分配到多种类型权重矩阵中，而不应该用更大的秩单独微调某种类型的权重矩阵。

class LoRALayer():
    def __init__(
        self, 
        r: int, 
        lora_alpha: int, 
        lora_dropout: float,
        merge_weights: bool,
    ):
        self.r = r
        self.lora_alpha = lora_alpha
        # Optional dropout
        if lora_dropout > 0.:
            self.lora_dropout = nn.Dropout(p=lora_dropout)
        else:
            self.lora_dropout = lambda x: x
        # Mark the weight as unmerged
        self.merged = False
        self.merge_weights = merge_weights

class Embedding(nn.Embedding, LoRALayer):
    # LoRA implemented in a dense layer
    def __init__(
        self,
        num_embeddings: int,
        embedding_dim: int,
        r: int = 0,
        lora_alpha: int = 1,
        merge_weights: bool = True,
        **kwargs
    ):
        nn.Embedding.__init__(self, num_embeddings, embedding_dim, **kwargs)
        LoRALayer.__init__(self, r=r, lora_alpha=lora_alpha, lora_dropout=0,
                           merge_weights=merge_weights)
        # Actual trainable parameters
        if r > 0:
            self.lora_A = nn.Parameter(self.weight.new_zeros((r, num_embeddings)))
            self.lora_B = nn.Parameter(self.weight.new_zeros((embedding_dim, r)))
            self.scaling = self.lora_alpha / self.r
            # Freezing the pre-trained weight matrix
            self.weight.requires_grad = False
        self.reset_parameters()

    def reset_parameters(self):
        nn.Embedding.reset_parameters(self)
        if hasattr(self, 'lora_A'):
            # initialize A the same way as the default for nn.Linear and B to zero
            nn.init.zeros_(self.lora_A)
            nn.init.normal_(self.lora_B)

    def train(self, mode: bool = True):
        nn.Embedding.train(self, mode)
        if mode:
            if self.merge_weights and self.merged:
                # Make sure that the weights are not merged
                if self.r > 0:
                    self.weight.data -= (self.lora_B @ self.lora_A).transpose(0, 1) * self.scaling
                self.merged = False
        else:
            if self.merge_weights and not self.merged:
                # Merge the weights and mark it
                if self.r > 0:
                    self.weight.data += (self.lora_B @ self.lora_A).transpose(0, 1) * self.scaling
                self.merged = True
        
    def forward(self, x: torch.Tensor):
        if self.r > 0 and not self.merged:
            result = nn.Embedding.forward(self, x)
            after_A = F.embedding(
                x, self.lora_A.transpose(0, 1), self.padding_idx, self.max_norm,
                self.norm_type, self.scale_grad_by_freq, self.sparse
            )
            result += (after_A @ self.lora_B.transpose(0, 1)) * self.scaling
            return result
        else:
            return nn.Embedding.forward(self, x)
            

class Linear(nn.Linear, LoRALayer):
    # LoRA implemented in a dense layer
    def __init__(
        self, 
        in_features: int, 
        out_features: int, 
        r: int = 0, 
        lora_alpha: int = 1, 
        lora_dropout: float = 0.,
        fan_in_fan_out: bool = False, # Set this to True if the layer to replace stores weight like (fan_in, fan_out)
        merge_weights: bool = True,
        **kwargs
    ):
        nn.Linear.__init__(self, in_features, out_features, **kwargs)
        LoRALayer.__init__(self, r=r, lora_alpha=lora_alpha, lora_dropout=lora_dropout,
                           merge_weights=merge_weights)

        self.fan_in_fan_out = fan_in_fan_out
        # Actual trainable parameters
        if r > 0:
            self.lora_A = nn.Parameter(self.weight.new_zeros((r, in_features)))
            self.lora_B = nn.Parameter(self.weight.new_zeros((out_features, r)))
            self.scaling = self.lora_alpha / self.r
            # Freezing the pre-trained weight matrix
            self.weight.requires_grad = False
        self.reset_parameters()
        if fan_in_fan_out:
            self.weight.data = self.weight.data.transpose(0, 1)

    def reset_parameters(self):
        nn.Linear.reset_parameters(self)
        if hasattr(self, 'lora_A'):
            # initialize B the same way as the default for nn.Linear and A to zero
            # this is different than what is described in the paper but should not affect performance
            nn.init.kaiming_uniform_(self.lora_A, a=math.sqrt(5))
            nn.init.zeros_(self.lora_B)

    def train(self, mode: bool = True):
        def T(w):
            return w.transpose(0, 1) if self.fan_in_fan_out else w
        nn.Linear.train(self, mode)
        if mode:
            if self.merge_weights and self.merged:
                # Make sure that the weights are not merged
                if self.r > 0:
                    self.weight.data -= T(self.lora_B @ self.lora_A) * self.scaling
                self.merged = False
        else:
            if self.merge_weights and not self.merged:
                # Merge the weights and mark it
                if self.r > 0:
                    self.weight.data += T(self.lora_B @ self.lora_A) * self.scaling
                self.merged = True       

    def forward(self, x: torch.Tensor):
        def T(w):
            return w.transpose(0, 1) if self.fan_in_fan_out else w
        if self.r > 0 and not self.merged:
            result = F.linear(x, T(self.weight), bias=self.bias)            
            result += (self.lora_dropout(x) @ self.lora_A.transpose(0, 1) @ self.lora_B.transpose(0, 1)) * self.scaling
            return result
        else:
            return F.linear(x, T(self.weight), bias=self.bias)


class MergedLinear(nn.Linear, LoRALayer):
    # LoRA implemented in a dense layer
    def __init__(
        self, 
        in_features: int, 
        out_features: int, 
        r: int = 0, 
        lora_alpha: int = 1, 
        lora_dropout: float = 0.,
        enable_lora: List[bool] = [False],
        fan_in_fan_out: bool = False,
        merge_weights: bool = True,
        **kwargs
    ):
        nn.Linear.__init__(self, in_features, out_features, **kwargs)
        LoRALayer.__init__(self, r=r, lora_alpha=lora_alpha, lora_dropout=lora_dropout,
                           merge_weights=merge_weights)
        assert out_features % len(enable_lora) == 0, \
            'The length of enable_lora must divide out_features'
        self.enable_lora = enable_lora
        self.fan_in_fan_out = fan_in_fan_out
        # Actual trainable parameters
        if r > 0 and any(enable_lora):
            self.lora_A = nn.Parameter(
                self.weight.new_zeros((r * sum(enable_lora), in_features)))
            self.lora_B = nn.Parameter(
                self.weight.new_zeros((out_features // len(enable_lora) * sum(enable_lora), r))
            ) # weights for Conv1D with groups=sum(enable_lora)
            self.scaling = self.lora_alpha / self.r
            # Freezing the pre-trained weight matrix
            self.weight.requires_grad = False
            # Compute the indices
            self.lora_ind = self.weight.new_zeros(
                (out_features, ), dtype=torch.bool
            ).view(len(enable_lora), -1)
            self.lora_ind[enable_lora, :] = True
            self.lora_ind = self.lora_ind.view(-1)
        self.reset_parameters()
        if fan_in_fan_out:
            self.weight.data = self.weight.data.transpose(0, 1)

    def reset_parameters(self):
        nn.Linear.reset_parameters(self)
        if hasattr(self, 'lora_A'):
            # initialize A the same way as the default for nn.Linear and B to zero
            nn.init.kaiming_uniform_(self.lora_A, a=math.sqrt(5))
            nn.init.zeros_(self.lora_B)

    def zero_pad(self, x):
        result = x.new_zeros((len(self.lora_ind), *x.shape[1:]))
        result[self.lora_ind] = x
        return result

    def merge_AB(self):
        def T(w):
            return w.transpose(0, 1) if self.fan_in_fan_out else w
        delta_w = F.conv1d(
            self.lora_A.unsqueeze(0), 
            self.lora_B.unsqueeze(-1), 
            groups=sum(self.enable_lora)
        ).squeeze(0)
        return T(self.zero_pad(delta_w))

    def train(self, mode: bool = True):
        def T(w):
            return w.transpose(0, 1) if self.fan_in_fan_out else w
        nn.Linear.train(self, mode)
        if mode:
            if self.merge_weights and self.merged:
                # Make sure that the weights are not merged
                if self.r > 0 and any(self.enable_lora):
                    self.weight.data -= self.merge_AB() * self.scaling
                self.merged = False
        else:
            if self.merge_weights and not self.merged:
                # Merge the weights and mark it
                if self.r > 0 and any(self.enable_lora):
                    self.weight.data += self.merge_AB() * self.scaling
                self.merged = True        

    def forward(self, x: torch.Tensor):
        def T(w):
            return w.transpose(0, 1) if self.fan_in_fan_out else w
        if self.merged:
            return F.linear(x, T(self.weight), bias=self.bias)
        else:
            result = F.linear(x, T(self.weight), bias=self.bias)
            if self.r > 0:
                result += self.lora_dropout(x) @ T(self.merge_AB().T) * self.scaling
            return result