New algorithms or improvements

• Reduce iterations of W&D to reduce the integration tests time in https://github.com/microsoft/recommenders/pull/1698
• Implementation of most frequent recommendation in https://github.com/microsoft/recommenders/pull/1666
• Implement time_now for sarplus in #1719 #1721
• Add a fast failure in SAR+ if the similarity metric is not within the options in https://github.com/microsoft/recommenders/pull/1743
• SAR item similarity dtype correction in https://github.com/microsoft/recommenders/pull/1751
• Simplify SAR test data loading functions in https://github.com/microsoft/recommenders/pull/1752
• Reformat SAR+ SQL queries in https://github.com/microsoft/recommenders/pull/1772
• Add new item similarity metrics for SAR in https://github.com/microsoft/recommenders/pull/1754

New utilities or improvements

• Rewrite get_top_k_items() to improve runtime in https://github.com/microsoft/recommenders/pull/1748
• Optimized Spark recall_at_k time performance in https://github.com/microsoft/recommenders/pull/1796

New notebooks or improvements

• Fix missing import in FastAI notebook https://github.com/microsoft/recommenders/pull/1708
• Review NCF notebook in #1703 #1712
• Review LigthFM notebook and add test in https://github.com/microsoft/recommenders/pull/1706
• Review BPR notebook in https://github.com/microsoft/recommenders/pull/1704
• Review LightGCN notebook in https://github.com/microsoft/recommenders/pull/1714
• Review DKN notebook in https://github.com/microsoft/recommenders/pull/1722
• Review SAR notebook #1738 #1768

Other features

• Enable distributed tests with AzureML #1696 #1717 #1729 #1733 #1739 #1747 #1732 #1755 #1763 #1771 #1773 #1775 #1787 #1788 #1794
• Added tests for Python 3.8 and 3.9 in https://github.com/microsoft/recommenders/pull/1756
• Image of contributors in https://github.com/microsoft/recommenders/pull/1692
• Update README.md in #1709 #1711 #1767
• Error in codeowners file in https://github.com/microsoft/recommenders/pull/1699
• Add test to check if CuDNN is enabled in https://github.com/microsoft/recommenders/pull/1715
• Update docker image reference to internal registry in https://github.com/microsoft/recommenders/pull/1727
• Fixed a link error in data_transform.ipynb in https://github.com/microsoft/recommenders/pull/1736
• Added tests for ranking function get_top_k_items() in https://github.com/microsoft/recommenders/pull/1757
• Fix memory error in CPU nightly workflow in https://github.com/microsoft/recommenders/pull/1759
• Update test infrastructure explanation #1776 #1777
• Added time performance tests in https://github.com/microsoft/recommenders/pull/1765
• Add path filter to avoid triggering unit tests when we change a markdown in https://github.com/microsoft/recommenders/pull/1791

Full Changelog: https://github.com/microsoft/recommenders/compare/1.1.0...1.1.1