问题:
- 深度学习训练的常规步骤
- 微调模型的几个思考方向
- 构建自己的数据集用于微调大模型
- 各种微调方式的实现
编写代码
先用一个简单的中文手写识别的深度学习例子来说明训练的过程,这里分别使用PyTorch和TenserFlow来实现,以便比较两个工具库的不同风格。
Talk is cheap, Show code.
数据存放的路径:总共15000张图片,可以去kaggle.com下载 www.kaggle.com/datasets/gp…
图片文件名最后一个数字和图片内容中的文字对应关系是:
[“零一二三四五六七八九十百千万亿”] -> index + 1
按咱的惯例,定义数据路径:
cur_path = os.getcwd()
class DataPathEnum(str, Enum):
ZH_HANDWRITTING_IMG_DIR = "chinese_handwritting/images"
GPT2XL_TRAIN_DATA_DIR = "gpt2xl"
MODEL_CHECKPOINT_DIR = "checkpoints"
def __str__(self):
return os.path.join(cur_path, "data", self.value)
然后定义两个类库都可以使用的数据基类:
IMAGE_DIR = str(DataPathEnum.ZH_HANDWRITTING_IMG_DIR)
# image = 64 * 64
class HWData():
def __init__(self) -> None:
self.jpg>"零一二三四五六七八九十百千万亿"
self.image_folder:str = IMAGE_DIR
# 获取图片路径和标签
def get_image_path_vs_lable(self, index):
image_file = self.image_files[index]
image_path = os.path.join(self.image_folder, image_file)
label = int(image_file.split(".")[0].split("_")[-1]) -1
return label, image_path
# 在ipynb文件展示图片并显示标签,以便和预测的结果进行比较
def plot_image(self, index):
label, image_path = self.get_image_path_vs_lable(index)
image = Image.open(image_path)
plt.title("label: " + str(label) + "/" + self.character_str[label])
plt.imshow(image)
先用PyTorch库来操作, 继承自torch.utils.data.Dataset实现自定义数据集,引入图像处理torchvision库。
class HWDataset(HWData, Dataset):
def __init__(self) -> None:
super().__init__()
self.transform = torchvision.transforms.ToTensor()
# 实现基类方法
def __len__(self):
return len(self.image_files)
# 实现基类方法
def __getitem__(self, index) -> Any:
label, image_path = self.get_image_path_vs_lable(index)
image_tensor = self.transform(Image.open(image_path))
# 标签向量,独热模式
target = torch.zeros((15))
target[label] = 1.0
return image_tensor, target, self.character_str[label]
# 随机抽一张图,做验证比较
def get_random_item(self):
index = randint(0, self.__len__() -1)
return self.__getitem__(index), index
继承自torch.nn.Module实现模型类:
class TorchClassifier(nn.Module):
def __init__(self) -> None:
super().__init__()
# 这里只构建全连接层,以便和后面加了卷积和池化层的模型进行比较
self.model = nn.Sequential(
nn.Linear(64*64, 1000), # 图片格式64x64
nn.LeakyReLU(0.02),
nn.Linear(1000, 100),
nn.LeakyReLU(0.02),
nn.LayerNorm(100),
nn.Linear(100, 15),
nn.Softmax(dim = 1)
)
# 定义优化函数
self.optimiser = torch.optim.Adam(self.parameters(), lr=0.001)
# 定义损失函数
self.loss = nn.BCELoss()
# 初始化数据集
self.dataset = HWDataset()
# 训练过程数据记录
self.counter = 0
self.progress = []
# 模型参数保存路径
self.checkpoint_file = os.path.join(str(DataPathEnum.MODEL_CHECKPOINT_DIR),
"zh_hw_torch.pth")
# 实现基类方法
def forward(self, x):
# 全连接层接受扁平的批次数据
x = x.view(x.size(0), -1) # 等同 nn.flatten(x)
return self.model(x)
# 训练方法
def _train(self, x, y):
outputs = self.forward(x)
loss = self.loss(outputs, y)
# 优化过程
self.optimiser.zero_grad() #重置,否则在下个批次梯度会叠加
loss.backward() #反向传播
self.optimiser.step() #调整每层的参数
# 记录过程数据(损失函数的值)
self.counter += 1
if(self.counter % 10 == 0):
self.progress.append(loss.item())
# 按周期次数进行训练
def train(self, epochs: int):
print('start train model...')
for epochs in range(epochs):
data_loader = DataLoader(self.dataset, batch_size=100, shuffle=True)
for index, (data, target, target_char) in enumerate(data_loader):
self._train(data, target)
self._plot_progress() #绘制训练过程中损失函数的值
# 随机抽一张图,验证查看
def random_eval_model(self):
(data, target, _), index = self.dataset.get_random_item()
self.dataset.plot_image(index)
with torch.no_grad():
output = self.forward(data)
df = pd.DataFrame(output.detach().numpy()).T
df.plot.barh(rot=0, legend=False, ylim=(0, 15), xlim=(0,1))
def _plot_progress(self):
df = pd.DataFrame(self.progress, columns = ["loss"])
df.plot(title="counter:" + str(self.counter), ylim=(0, 1.0), figsize=(16,8),
alpha=0.5, marker=".", grid=True, yticks=(0,0.25,0.5))
# 保存模型参数
def save_model_state(self):
torch.save(self.model.state_dict(), self.checkpoint_file)
写个ipynb文件来调用模型进行训练:
from aitrain.classifier_torch import HWDataset, TorchClassifier
#测试数据集
dataset = HWDataset()
dataset.plot_image(2)
# 训练模型并保存参数
classifier = TorchClassifier()
classifier.train(3)
classifier.save_model_state()
# 随机验证并比较预测结果
classifier.random_eval_model()
下面用TensorFlow2来实现相同的模块和功能,以便比较两种类库的操作区别。 继承自tensorflow.keras.utils.Sequence实现数据集
class TFDataset(HWData, tf.keras.utils.Sequence):
def __init__(self, batch_size) -> None:
super().__init__()
self.batch_size = batch_size
# 实现基类方法,这里返回的批次
def __len__(self):
return math.ceil(len(self.jpg># 实现基类方法,依然是批次数据
def __getitem__(self, idx):
low = idx * self.batch_size
high = min(low + self.batch_size, len(self.image_files))
image_list = []
label_list = []
for index in range(low, high):
label, image_path = self.get_image_path_vs_lable(index)
image_array = np.array(list(Image.open(image_path).getdata()))
image_list.append(image_array)
# 标签的独热模式
target =[0 if label != i else 1 for i in range(15)]
label_list.append(target)
# 返回的是批次数据,注意shape与模型的输入参数一致
return np.array(image_list).reshape(-1,64,64,1), np.array(label_list)
# 实现基类方法,每个训练周期结束后调用
def on_epoch_end(self):
random.shuffle(self.image_files)
使用tensorflow.keras.Sequential构建TF模型,这里添加卷积和池化层,只是比较一下两个模型的预测准确率。
class TFClassifier():
def __init__(self, data: TFDataset) -> None:
model = tf.keras.Sequential()
layers = tf.keras.layers
model.add(layers.Rescaling(1./255)) # 压缩到0 ~ 1
model.add(layers.Conv2D(filters=32, kernel_size=(3, 3), strides=(1, 1), activation='relu',
input_shape=(64, 64, 1)))
model.add(layers.MaxPool2D(pool_size=(2, 2), strides=(2, 2)))
model.add(layers.Conv2D(filters=64, kernel_size=(3, 3), strides=(1, 1), activation='relu'))
model.add(layers.MaxPool2D(pool_size=(2, 2), strides=(2, 2)))
model.add(layers.Conv2D(filters=128, kernel_size=(3, 3), strides=(1, 1), activation='relu'))
model.add(layers.MaxPool2D(pool_size=(2, 2), strides=(2, 2)))
model.add(layers.Flatten()) #扁平层连接卷积层和全连接层
model.add(layers.Dense(units=1024, activation='relu'))
model.add(layers.Dropout(0.2)) # 丢弃一些特征
model.add(layers.Dense(units=256, activation='relu'))
model.add(layers.Dense(units=15, activation='softmax'))
model.compile(optimizer="adam", loss="categorical_crossentropy", metrics=["accuracy"])
self.model = model
self.data = data
self.checkpoint_file = os.path.join(str(DataPathEnum.MODEL_CHECKPOINT_DIR),
"zh_hw_tf.h5")
# 训练模型
def train(self, epochs):
his = self.model.fit(self.data, epochs=epochs, verbose=2).history #
self.__plot_history(his)
self.model.summary() # 模型概要
# 随机选图对比验证
def random_eval_model(self):
index = random.randint(0, len(self.data.image_files)-1)
self.data.plot_image(index)
label, image_path= self.data.get_image_path_vs_lable(index)
image_array = np.array(list(Image.open(image_path).getdata())).reshape(-1, 64, 64, 1)
prediction = self.model.predict(image_array)
df = pd.DataFrame(prediction[0])
df.plot.barh(rot=0, legend=False, ylim=(0, 15), xlim=(0,1))
# 保存模型参数
def save_model_weights(self):
self.model.save_weights(self.checkpoint_file)
def load_model_weights(self):
self.model.load_weights(self.checkpoint_file)
# 绘制历史数据,这里没有导入验证数据集,所以没有与验证相关损失函数值
def __plot_history(self, history):
fig, axs = plt.subplots(1, 2, figsize=(10, 5))
axs[0].plot(history['loss'], label='training loss')
# axs[0].plot(history['val_loss'], label='validation loss')
axs[0].legend(loc='upper left')
axs[0].set_title('training data vs validation data')
axs[1].plot(history['accuracy'], label='testing accuracy')
# axs[1].plot(history['val_accuracy'], label='validation accuracy')
axs[1].set_ylim([0, 1])
axs[1].legend(loc='upper left')
axs[1].set_title('accuracy')
axs.flat[0].set(xlabel='epochs', ylabel='loss')
axs.flat[1].set(xlabel='epochs', ylabel='accuracy')
plt.show()
写个ipynb文件来调用模型进行训练:
from aitrain.classifier_tensorflow import TFDataset, TFClassifier
# 验证数据集
data = TFDataset(100)
data.plot_image(5)
# 训练模型
classifier = TFClassifier(data)
classifier.train(3)
classifier.save_model_weights()
classifier.random_eval_model()
从构建数据集和模型的方式,可见TensorFlow和PyTorch封装的方式不同,但是都能方便地实现自己的想法。后面提到的transformers可以很好的融合这两个深度学习库。
从问题解决的角度看,与问题相适应的复杂度模型会很好地平衡训练时间和预测准确度,所以说优化方法和思维方式一直都是不断提高AI能力的推动力。
下一篇谈谈巨量参数的语言模型,如何在降低参数精度载入、增加AB低秩矩阵Tuning层来节省Full Fine-Tunning全量微调的计算资源需求。