I trained a [context2vec].(https://github.com/orenmel/context2vec/blob/master/context2vec/train/train_context2vec.py)
I printed the context_v in explore_context2vec.py, and got all nan.
When using tensorflow, I can fix this by adding a small number to the loss function.

cross_entropy = self.target * tf.log(self.prediction+1e-10)
How to do this in chainer?