DiveRS'11

Pablo Castells, Jun Wang, Ruben Lara, and Dell Zhang are organising an ACM RecSys-2011 workshop on Novelty and Diversity in Recommender Systems (DiveRS). A special issue of ACM TIST in the scope of the workshop will be announced after the conference. Authors of accepted papers will be invited to submit an extended version.

A couple of metrics

It is often desirable to measure the dissimilarity or distance between items using a proper metric.

• Jaccard coefficient can be converted to a metric by by subtracting the Jaccard coefficient from 1.
• Kullback–Leibler divergence can be converted to a metric by taking the square root of its symmetric version Jensen–Shannon divergence.

A Poor Man's Parallel Processing

A very crude, but often good enough, method to achieve parallel processing (e.g., on multi-core computers) is to partition the large input data file into small chunks, run the program to process each of them in parallel, and then merge the output results file back. Fortunately, this process can be done easily with the wise iterative usage of two Unix utilities: split and cat.

nDCG

The choice of the gain and discount function for the popular IR performance measure normalised Discounted Cumulative Gain (nDCG) has been discussed and empirically justified in a CIKM-2009 paper through analysis of variance (ANOVA).

LNRE

Here is a good tutorial with Matlab examples about Statistical Estimation for Large Numbers of Rare Events (LNRE).