Whenever you want to create machine intelligence model, the first question to ask is “Where is my data?”. It is usually difficult to find good data to create models because it is time-consuming and may require costs to do that. Unless you work in good companies such as Google or Facebook, it might be a headache for you. But fortunately, there are good ways to solve this problem. It is “Transfer learning”. Let us find out!
1. Transfer learning
When we need to train machine intelligence models, we usually use “supervised learning”. It means that we need “teachers” who can tell which is a right answer. For example, when we need to classify “which is a cat or a dog?”, we need to tell “this is a cat and that is a dog” to computers. It is the powerful method of learning to achieve higher accuracy. So most of the current AI applications are developed by “Supervised learning”. But a problem arises here. There are a little data for supervised learning. While we have many images on our smartphones, each image has no information about “what it is”. So we need to add this information to each image manually. It takes time to complete as a massive amount of images are needed in training. I explained it a little in computer vision in my blog before. We can say the same thing in text analysis or natural language processing. We have many tweets on the internet. But no one tells you which has positive and negative sentiment. Therefore we need to put “positive or negative’ to each tweet by ourselves. No one wants to do that. Then “Transfer learning” comes here. You do not need training from scratch. Just transfer someone’s results to your models as someone did the similar training before you do! The beauty of “Transfer Learning” is that we need just a little data in our training. No need for a massive amount of data anymore. It makes preparing data far easier for us!
This model (1) is one of the most sophisticated models for machine translation in 2017. It is created by Google brain. As you know, it achieved the state of art of accuracy in Neural Machine translation at the time it was public. The key architecture of Transformer is “Self-attention”. It can tell us where the model should pay attention to among all words in a sentence, regardless of their respective position, by using “Query, Key, and Value” mechanism. The Research paper “Attention Is All You Need” is available here. “Self-attention mechanism” takes times to explain in details. If you want to know more, this blog is strongly recommended. I just want to say “Self-attention mechanism” might be a game changer to develop machine intelligence in the future.
3. Transfer learning based on “Transformer”
It has been more than one year since “Transformer” was public, There are several variations based on”Transformer”. I found the good model for “transfer learning” I mentioned earlier in this article. This is “Universal Sentence Encoder“(2). In this website, we can find a good explanation of what it is.
“The Universal Sentence Encoder encodes text into high dimensional vectors that can be used for text classification, semantic similarity, clustering and other natural language tasks.”
The model takes sentences, phrases or short paragraphs and outputs vectors to be fed into the next process. “The universal-sentence-encoder-large” is trained with “Transformer” (-light is trained with a different model). The beauty is that Universal Sentence Encoder is already trained by Google and these results are available to perform “transfer learning” by ourselves. This is great! This chart tells you how it works.
The team in Google claimed that “With transfer learning via sentence embeddings, we observe surprisingly good performance with minimal amounts of supervised training data for a transfer task.”. So let me confirm how it works with a little data. I performed a small experiment based on this awesome article. I modify the classification model and change the number of training samples. With only 100 training data, I could achieve 79.2% accuracy. With 300 data, 95.8% accuracy. This is great! I believe the results come from the power of transfer learning with Universal Sentence Encoder.
In this article, I introduce transfer learning and perform a small experiment with the latest model “Universal Sentence Encoder”. It looks very promising so far. I would like to continue transfer learning experiments and update the results here. Stay tuned!
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- Attention Is All You Need, Ashish Vaswani, Noam Shazeer, Niki Parmar, Jakob Uszkoreit, Llion Jones, Aidan N. Gomez, Lukasz Kaiser, Illia Polosukhin, Google, 12 June 2017.
- Universal Sentence Encoder, Daniel Cer, Yinfei Yang, Sheng-yi Kong, Nan Hua, Nicole Limtiaco, Rhomni St. John, Noah Constant, Mario Guajardo-Cespedes, Steve Yuan, Chris Tar, Yun-Hsuan Sung, Brian Strope, Ray Kurzweil, Google, 29 March 2018
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