[MAHOUT-317] Collocations: Eliminate in-memory frequency calculation

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.3
• Fix Version/s: 0.3
• Assignee: Drew Farris
• Reporter: Drew Farris
• Created: 01/Mar/10 05:21
• Updated: 11/Mar/10 02:14
• Resolved: 06/Mar/10 16:39

Description

see: http://www.lucidimagination.com/search/document/ae484d53e969250e/who_owns_mahout_bucket_on_s3

The collocation code currently uses maps in the CollocCombiner and CollocReducer to perform frequency calculations which can cause the process to exceed the heap space if a large number of ngrams exist for any given subgram.

Convert the code to use a composite key / secondary sort to avoid the need for in-memory map for frequency calculations.