[MAHOUT-824] FastByIDRunningAverage: Optimize SlopeOneRecommender by optimizing MemoryDiffStorage

• Type: Improvement
• Status: Closed
• Priority: Trivial
• Resolution: Won't Fix
• Fix Version/s: 0.6
• Assignee: Sean R. Owen
• Reporter: Lance Norskog
• Created: 02/Oct/11 01:49
• Updated: 09/Feb/12 14:00
• Resolved: 02/Oct/11 07:04

Description

The SlopeOneRecommender has by far the best RMS of all of the online recommenders in Mahout (that I've found). Unfortunately the implementation also uses much more memory and is unuseable on my laptop.

This patch optimizes memory (and speed) by folding FastByIDMap<RunningAverage> into one class: FastByIDRunningAverage. This is what it sounds like: a Long-addressable array of running averages (and optionally standard deviation).