EnvironmentsOnline and OfflineUser Versus Item MetricsA/B TestingRecall and Precision@ kPrecision at kRecall at kR-precisionmAP, MMR, NDCGmAPMRRNDCGmAP Versus NDCG?Correlation CoefficientsRMSE from AffinityIntegral Forms: AUC and cAUCRecommendation Probabilities to AUC-ROCComparison to Other MetricsBPRSummary