LSTM 模型的问题

Question

我尝试在 PyTorch 中实现 LSTM 模型并遇到这样的问题：损失不减少。 我的任务是这样的：我有不同功能的会话。会话长度是固定的，等于 20。我的目标是预测最后一个会话是否被跳过。 我尝试缩放输入特征，我尝试将target 传递给特征（可能提供的特征绝对没有信息，我认为这会导致过度拟合并且损失应该接近 0），但我的损失减少总是如下所示：

print(X.shape)
#(82770, 20, 31) where 82770 is count of sessions, 20 is seq_len, 31 is count of features
print(y.shape)
#(82770, 20)

我还定义了get_batches 函数。是的，我知道这个生成器中最后一批的问题

def get_batches(X, y, batch_size):
'''Create a generator that returns batches of size
   batch_size x seq_length from arr.
'''
assert X.shape[0] == y.shape[0]
assert X.shape[1] == y.shape[1]
assert len(X.shape) == 3
assert len(y.shape) == 2

seq_len = X.shape[1]
n_batches = X.shape[0]//seq_len

for batch_number in range(n_batches):
    #print(batch_number*batch_size, )
    batch_x = X[batch_number*batch_size:(batch_number+1)*batch_size, :, :]
    batch_y = y[batch_number*batch_size:(batch_number+1)*batch_size, :]
    if batch_x.shape[0] == batch_size:
        yield batch_x, batch_y
    else:
        print('batch_x shape: {}'.format(batch_x.shape))
        break

这是我的 RNN

class BaseRNN(nn.Module):

def __init__(self, n_features, hidden_size, n_layers, drop_p=0.3, lr=0.001, last_items=10):
    super(BaseRNN, self).__init__()
    # constants
    self.n_features = n_features
    self.hidden_size = hidden_size
    self.n_layers = n_layers 
    self.drop_p = drop_p
    self.lr = lr
    self.last_items = last_items

    # layers
    self.lstm = nn.LSTM(
        n_features, n_hidden, n_layers, 
        dropout=drop_p, batch_first=True
    )
    self.dropout = nn.Dropout(self.drop_p)
    self.linear_layer = nn.Linear(self.hidden_size, 1)
    self.sigm = nn.Sigmoid()

def forward(self, x, hidden):
    out, hidden = self.lstm(x, hidden)
    batch_size = x.shape[0]
    out = self.dropout(out)
    out = out.contiguous().view(-1, self.hidden_size)
    out = self.linear_layer(out)
    out = self.sigm(out)
    # use only last elements
    out = out.view(batch_size, -1)
    out = out[:, -1] 
    return out, hidden

def init_hidden(self, batch_size):
    #initialize with zeros
    weight = next(self.parameters()).data
    hidden = (weight.new(self.n_layers, batch_size, self.hidden_size).zero_(),
                  weight.new(self.n_layers, batch_size, self.hidden_size).zero_())

    return hidden

这是我的火车功能：

def train(net, X, y,
      n_epochs=10, batch_size=10, clip=5):
'''
pass
'''
n_features = X.shape[2]
seq_len = X.shape[1]
net.train()
opt = torch.optim.Adam(net.parameters(), lr=net.lr)
criterion = nn.BCELoss()
counter = 0
losses = []
for e in range(n_epochs):
    h = net.init_hidden(batch_size)
    for x, y in get_batches(X=X, y=y, batch_size=batch_size):
        counter += 1
        h = net.init_hidden(batch_size)
        inputs, targets = torch.from_numpy(x).float(), torch.from_numpy(y.astype(int))
        targets = targets[:,-net.last_items:].float().view(net.last_items*batch_size)
        h = tuple([each.data for each in h])
        net.zero_grad()
        output, h = net(inputs, h)
        loss = criterion(output.view(net.last_items*batch_size), targets)
        losses.append(loss.item())
        loss.backward()
        nn.utils.clip_grad_norm_(net.parameters(), clip)
        opt.step()
return losses

运行训练：

n_hidden = 100
n_layers = 1
n_features = X.shape[2]
net = BaseRNN(n_features, n_hidden, n_layers, 
              lr=0.01, drop_p=0.1, last_items=1)

losses = train(net, X, y, n_epochs=5, batch_size=1000, lr=0.001, clip=5)
plt.plot(losses)

在所有这些步骤之后，我得到了问题顶部的情节。我认为我在某个地方遇到了一个巨大的错误，因为我将目标变量放在了特征中，但仍然没有减少损失。 我哪里错了？

PS.如何生成样本数据？我将使用真实的y 数据并添加一些噪音。

Y = np.array([[0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 1],
       [1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
       [0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
       [1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1],
       [0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0],
       [0, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
       [0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
       [1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
       [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1],
       [1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1]])
print(Y.shape)
#(10, 20)

# add 5 features with random noise 
random_noise = np.random.randn(10*20*5).reshape(10,20,5)
X = np.concatenate((Y.reshape(10,20,1), random_noise), axis=2)
print(X.shape)
#(10, 20, 6)

Answer 1

我的失败，忘记缩放输入功能，现在可以正常工作。