pytorch保存并加载模型

当我们的模型训练好之后，需要将其参数（或整个模型）保存起来以便日后直接使用。pytorch提供了两种方法帮助我们快速、方便地保存训练好的模型

步骤

• 训练模型
• 保存模型
• 加载模型

训练模型

我们以二分类问题为例，训练一个神经网络，代码如下：

import torch
import torch.nn.functional as F
import matplotlib.pyplot as plt


n_data = torch.ones(100, 2)
x0 = torch.normal(2 * n_data, 1)
y0 = torch.zeros(100)
x1 = torch.normal(-2 * n_data, 1)
y1 = torch.ones(100)
x = torch.cat((x0, x1), 0).type(torch.FloatTensor)
y = torch.cat((y0, y1)).type(torch.LongTensor)


class Net(torch.nn.Module):
    def __init__(self, input_size, hidden_size, output_size):
        super().__init__()
        self.linear1 = torch.nn.Linear(input_size, hidden_size)
        self.pred = torch.nn.Linear(hidden_size, output_size)

    def forward(self, x):
        output = F.relu(self.linear1(x))
        output = self.pred(output)
        return output


def train(epochs):
    model = Net(2, 64, 2)
    optimi = torch.optim.SGD(model.parameters(), lr=0.001)
    loss_fn = torch.nn.CrossEntropyLoss()

    for epoch in range(epochs):
        out = model(x)
        loss = loss_fn(out, y)  # 一定要预测在前，真实值在后

        optimi.zero_grad()
        loss.backward()
        optimi.step()

        if (epoch + 1) % 50 == 0:
            print("epoch [{}]/[{}], loss: {:.4f}".format(epoch + 1, epochs, loss.item()))
        if epoch == epochs - 1:
            draw(out, y)

保存模型

• 方法一：torch.save(model, "model_name.pkl")。该方法会将整个模型都保存下来
• 方法二：torch.save(model.state_dict(), "model_name.pkl") 该方法只保留模型参数

推荐使用第二种方法，据说速度快

加载模型

方法一：

print("加载整个模型........")
model = torch.load("model.pkl")
pred = model(x)

方法二：

print("配置模型参数........")
model2 = Net(2, 64, 2)
model2.load_state_dict(torch.load("model_param.pkl"))
pred2 = model2(x)

示例

用上述方法加载的两个模型，在同一数据集上运行结果应该是一样的：

加载整个模型的绘图结果	加载模型参数的绘图结果

完整代码

import torch
import torch.nn.functional as F
import matplotlib.pyplot as plt


n_data = torch.ones(100, 2)
x0 = torch.normal(2 * n_data, 1)
y0 = torch.zeros(100)
x1 = torch.normal(-2 * n_data, 1)
y1 = torch.ones(100)
x = torch.cat((x0, x1), 0).type(torch.FloatTensor)
y = torch.cat((y0, y1)).type(torch.LongTensor)


class Net(torch.nn.Module):
    def __init__(self, input_size, hidden_size, output_size):
        super().__init__()
        self.linear1 = torch.nn.Linear(input_size, hidden_size)
        self.pred = torch.nn.Linear(hidden_size, output_size)

    def forward(self, x):
        output = F.relu(self.linear1(x))
        output = self.pred(output)
        return output


def draw(pred, y):
    pred = torch.max(F.log_softmax(pred, dim=1), 1)[1]
    pred_y = pred.data.numpy().squeeze()
    target_y = y.numpy()
    plt.scatter(x.data.numpy()[:, 0], x.data.numpy()[:, 1], c=pred_y)
    accuracy = sum(pred_y == target_y) / 200
    plt.text(1.5, -4, "Accuracy=%.2f" % accuracy)
    plt.show()


def train(epochs):
    model = Net(2, 64, 2)
    optimi = torch.optim.SGD(model.parameters(), lr=0.001)
    loss_fn = torch.nn.CrossEntropyLoss()

    for epoch in range(epochs):
        out = model(x)
        loss = loss_fn(out, y)  # 一定要预测在前，真实值在后

        optimi.zero_grad()
        loss.backward()
        optimi.step()

        if (epoch + 1) % 50 == 0:
            print("epoch [{}]/[{}], loss: {:.4f}".format(epoch + 1, epochs, loss.item()))
        if epoch == epochs - 1:
            draw(out, y)

    torch.save(model, "model.pkl")  # 保存整个网络
    torch.save(model.state_dict(), "model_param.pkl")  # 只保留模型参数
    print("模型保存成功！！！")


if __name__ == "__main__":
    # train(100)
    print("加载整个模型........")
    model = torch.load("model.pkl")
    pred = model(x)
    draw(pred, y)

    print("配置模型参数........")
    model2 = Net(2, 64, 2)
    model2.load_state_dict(torch.load("model_param.pkl"))
    pred2 = model2(x)
    draw(pred2, y)