Question: What is used to optimize the loss function?
Evidence: It is often the case that the meaning of a word is determined by its context, such as the previous word and the following word. [id=lq]Also, negations and emotion transitions are context sensitive. However, the memory network described in Section SECREF3 has only one memory slot with size INLINEFORM0 to represent a clause, where INLINEFORM1 is the dimension of a word embedding and INLINEFORM2 is the length of a clause. It means that when the memory network models a clause, it only considers each word separately.
In order to capture [id=lq]context information for clauses, we propose a new architecture which contains more memory slot to model the context with a convolutional operation. The basic architecture of Convolutional Multiple-Slot Memory Network (in short: ConvMS-Memnet) is shown in Figure 4.
Considering the text length is usually short in the dataset used here for emotion cause extraction, we set the size of the convolutional kernel to 3. That is, the weight of word INLINEFORM0 [id=lq]in the INLINEFORM1 -th position considers both the previous word INLINEFORM2 and the following word INLINEFORM3 by a convolutional operation: DISPLAYFORM0 
For the first and the last word in a clause, we use zero padding, INLINEFORM0 , where INLINEFORM1 is the length of a clause. Then, the attention [id=lq]weightsignal for each word position in the clause is [id=lq]now defined as: DISPLAYFORM0 
Note that we obtain the attention for each position rather than each word. It means that the corresponding attention for the INLINEFORM0 -th word in the previous convolutional slot should be INLINEFORM1 . Hence, there are three prediction output vectors, namely, INLINEFORM2 , INLINEFORM3 , INLINEFORM4 : DISPLAYFORM0 
At last, we concatenate the three vectors as INLINEFORM0 for the prediction by a softmax function: DISPLAYFORM0 
Here, the size of INLINEFORM0 is INLINEFORM1 . Since the prediction vector is a concatenation of three outputs. We implement a concatenation operation rather than averaging or other operations because the parameters in different memory slots can be updated [id=lq]respectively in this way by back propagation. The concatenation of three output vectors forms a sequence-level feature which can be used in the training. Such a feature is important especially [id=lq]when the size of annotated training data is small.
For deep architecture with multiple layer[id=lq]s training, the network is more [id=lq]complex (shown in Figure 5).
For the first layer, the query is an embedding of the emotion word, INLINEFORM0 .
In the next layer, there are three input queries since the previous layer has three outputs: INLINEFORM0 , INLINEFORM1 , INLINEFORM2 . So, for the INLINEFORM3 -th layer ( INLINEFORM4 ), we need to re-define the weight function (5) as:
In the last layer, [id=lq]the concatenation of the three prediction vectors form the final prediction vector to generate the answer.
For model training, we use stochastic gradient descent and back propagation to optimize the loss function. Word embeddings are learned using a skip-gram model. The size of the word embedding is 20 since the vocabulary size in our dataset is small. The dropout is set to 0.4.
For model training, we use stochastic gradient descent and back propagation to optimize the loss function.
Answer: The authors use stochastic gradient descent and back propagation to optimize the loss function.