# Recommendation {% dynamic if request.tld != 'cn' %}{% dynamic endif %}

Personalized recommendations are widely used for a variety of use cases on mobile devices, such as media content retrieval, shopping product suggestion, and next app recommendation. If you are interested in providing personalized recommendations in your application while respecting user privacy, we recommend exploring the following example and toolkit. Note: To customize a model, try [TensorFlow Lite Model Maker](https://www.tensorflow.org/lite/guide/model_maker). ## Get started

We provide a TensorFlow Lite sample application that demonstrates how to recommend relevant items to users on Android. Android example If you are using a platform other than Android, or you are already familiar with the TensorFlow Lite APIs, you can download our starter recommendation model. Download starter model We also provide training script in Github to train your own model in a configurable way. Training code ## Understand the model architecture We leverage a dual-encoder model architecture, with context-encoder to encode sequential user history and label-encoder to encode predicted recommendation candidate. Similarity between context and label encodings is used to represent the likelihood that the predicted candidate meets the user's needs. Three different sequential user history encoding techniques are provided with this code base: * Bag-of-words encoder (BOW): averaging user activities' embeddings without considering context order. * Convolutional neural network encoder (CNN): applying multiple layers of convolutional neural networks to generate context encoding. * Recurrent neural network encoder (RNN): applying recurrent neural network to encode context sequence. To model each user activity, we could use the ID of the activity item (ID-based) , or multiple features of the item (feature-based), or a combination of both. The feature-based model utilizing multiple features to collectively encode users’ behavior. With this code base, you could create either ID-based or feature-based models in a configurable way. After training, a TensorFlow Lite model will be exported which can directly provide top-K predictions among the recommendation candidates. ## Use your training data In addition to the trained model, we provide an open-sourced [toolkit in GitHub](https://github.com/tensorflow/examples/tree/master/lite/examples/recommendation/ml) to train models with your own data. You can follow this tutorial to learn how to use the toolkit and deploy trained models in your own mobile applications. Please follow this [tutorial](https://github.com/tensorflow/examples/tree/master/lite/examples/recommendation/ml/ondevice_recommendation.ipynb) to apply the same technique used here to train a recommendation model using your own datasets. ## Examples As examples, we trained recommendation models with both ID-based and feature-based approaches. The ID-based model takes only the movie IDs as input, and the feature-based model takes both movie IDs and movie genre IDs as inputs. Please find the following inputs and outputs examples. Inputs * Context movie IDs: * The Lion King (ID: 362) * Toy Story (ID: 1) * (and more) * Context movie genre IDs: * Animation (ID: 15) * Children's (ID: 9) * Musical (ID: 13) * Animation (ID: 15) * Children's (ID: 9) * Comedy (ID: 2) * (and more) Outputs: * Recommended movie IDs: * Toy Story 2 (ID: 3114) * (and more) Note: The pretrained model is built based on [MovieLens](https://grouplens.org/datasets/movielens/1m/) dataset for research purpose. ## Performance benchmarks Performance benchmark numbers are generated with the tool [described here](https://www.tensorflow.org/lite/performance/benchmarks).

Model Name	Model Size	Device	CPU
recommendation (movie ID as input)	0.52 Mb	Pixel 3	0.09ms*
		Pixel 4	0.05ms*

recommendation (movie ID and movie genre as inputs)	1.3 Mb	Pixel 3	0.13ms*
		Pixel 4	0.06ms*

\* 4 threads used. ## Use your training data In addition to the trained model, we provide an open-sourced [toolkit in GitHub](https://github.com/tensorflow/examples/tree/master/lite/examples/recommendation/ml) to train models with your own data. You can follow this tutorial to learn how to use the toolkit and deploy trained models in your own mobile applications. Please follow this [tutorial](https://github.com/tensorflow/examples/tree/master/lite/examples/recommendation/ml/ondevice_recommendation.ipynb) to apply the same technique used here to train a recommendation model using your own datasets. ## Tips for model customization with your data The pretrained model integrated in this demo application is trained with [MovieLens](https://grouplens.org/datasets/movielens/1m/) dataset, you may want to modify model configuration based on your own data, such as vocab size, embedding dims and input context length. Here are a few tips: * Input context length: The best input context length varies with datasets. We suggest selecting input context length based on how much label events are correlated with long-term interests vs short-term context. * Encoder type selection: we suggest selecting encoder type based on input context length. Bag-of-words encoder works well for short input context length (e.g. <10), CNN and RNN encoders bring in more summarization ability for long input context length. * Using underlying features to represent items or user activities could improve model performance, better accommodate fresh items, possibly down scale embedding spaces hence reduce memory consumption and more on-device friendly.