在Theano中查看RBM的费用更新

Question

我具有以下theano功能

train_rbm = theano.function(
    [index],
    cost,
    updates=updates,
    givens={
        x: train_set_x[index * batch_size: (index + 1) * batch_size]
    },
    name='train_rbm'
)

然后对于每个时期，我记录成本函数中的值

for epoch in range(training_epochs):
    mean_cost = []
    for batch_index in range(n_train_batches):
        mean_cost += [train_rbm(batch_index)]

    print('Training epoch %d, cost is ' % epoch, np.mean(mean_cost))

但是在进行训练时我得到了

Training epoch 0, cost is  nan   
Training epoch 1, cost is  nan

是因为我的Theano函数没有任何输出吗？在这种情况下如何定义？

如果您需要参考来完成完整的源代码，我将关注this tutorial