An application of the LightFM hybrid recommender system library for suggesting CDN (content delivery network) providers to various websites. Includes examples of using LightFM to create both hybrid and pure collaborative filtering recommendation models, scikit-optimize to run hyperparameter efficient searches, and matplotlib to visualize the models' learning curves. Detailed write-up here.

(Created at Tsinghua University's Big Data Technology R&D Center as part of USC Viterbi's Research Overseas program.)

If you use this repo for your work, please cite the corresponding DOI:

Content Delivery Networks (CDNs) are great for getting your digital content onto the devices of end-users around the world in an efficient way; however, there are so many different CDN providers and services available now that it can be hard for new internet content providers (ICPs) to know which service to pick.

Using data on Chinese ICPs from some researchers in Nanjing, China, I formulated CDN selection as a recommender systems problem, with ICPs as users and CDN providers as items. I first constructed an interactions matrix of existing CDN purchases, as well as feature vectors for both the ICPs and CDNs in the dataset. The result was a hybrid recommender system model that could suggest CDN providers to ICPs in both warm-start and cold-start scenarios.

Although I don't have permission to release the raw data (I've hidden the actual CDN provider names, along with most of the raw ICP/CDN data tables), this project may still serve as a valuable first step (or perhaps even just a proof of concept) toward future applications of recommender systems for CDN selection.

If you would like to run the main notebook locally, you'll need:

• Python >= 2.7, preferably via Anaconda
• The SciPy Stack (included in Anaconda builds)
• LightFM Recommender System Library (available via pip)
• Scikit-Optimize (available via pip)

Then, clone this repository, create a Jupyter session within the repo directory, and open the LightFM.ipynb file.

• LightFM.ipynb - Main recommender system notebook
• Read_Interactions.ipynb - Interactions preprocessing (not runnable)
• Read_ICP_Features.ipynb - User (ICP) feature preprocessing (not runnable)
• Read_CDN_Features.ipynb - Item (CDN) feature preprocessing (not runnable)

• 20170629-interactions-mappings.pkl - (interactions, iidx_to_cdn, cdn_to_iidx, uidx_to_icp, icp_to_uidx) tuple
  • Interactions: rows = users (ICPs), cols = items (CDNs), nonzero entries = interactions (CSR-sparse matrix)
  • icp_to_uidx: ICP name to user index mapping (Python dict)
  • uidx_to_icp: User index to ICP name mapping (Python dict)
  • cdn_to_iidx: CDN code to item index mapping (Python dict)
  • iidx_to_cdn: Item index to CDN code mapping (Python dict)
• 20170703-cdn-feature-vectors.pkl - cdn_features array. Rows = one-hot feature vectors (CSR-sparse matrix)
• 20170703-icp-feature-vectors.pkl - icp_features array. Rows = one-hot feature vectors (CSR-sparse matrix)
• 20170705-train-test.pkl - (train, test) matrices tuple (CSR-sparse matrices)
• 20170705-warm-cold.pkl - (test_warm, test_cold) matrices tuple (CSR-sparse matrices)
• 20170714-opt-models.pkl - tuple of trained LightFM model objects
  • Order: (opt_model_all, opt_model_none, opt_model_icp, opt_model_cdn)
• 20170714-opt-hyperparams.pkl - tuple of optimal hyperparameters for each model
  • Order: (opt_hyperparams_all, opt_hyperparams_none, opt_hyperparams_icp, opt_hyperparams_cdn)
  • Each element contains: (opt_epochs_[name], opt_lr_[name], opt_no_components_[name], opt_item_alpha_[name], opt_user_alpha_[name])

• LightFM - Recommender System Library
• Pandas - Data Preprocessing
• Scikit-optimize - Hyperparameter Optimization
• Scikit-learn - For feature vectorization
• Numpy/Scipy - For everything matrix-related

• Project Wiki
• Project Slides (PPT)

• Professor Yin Hao, Professor Yu Longqiang (Tsinghua University)
• Zha Cong - My host/partner student at Tsinghua University
• Mr. Feng Deng - Donor and creator of the USC Viterbi/Tsinghua Summer Research Program
• Maciej Kula (Lyst) - LightFM Author
• Ethan Rosenthal - For his blog posts on recommender systems