Mahout movieLens recommender, where are the output files?

Question

I am running mahout Recommender located in the mahout wiki stater, following a successful build after the comand:

mvn exec:java -Dexec.mainClass="org.apache.mahout.cf.taste.example.grouplens.GroupLensRecommenderEvaluatorRunner" -Dexec.args="-i ratings.dat"

I see this log file and could not find any output:

[INFO] Scanning for projects...
[INFO] Searching repository for plugin with prefix: 'exec'.
[INFO] ------------------------------------------------------------------------
[INFO] Building Mahout Examples
[INFO]    task-segment: [exec:java]
[INFO] ------------------------------------------------------------------------
[INFO] Preparing exec:java
[INFO] No goals needed for project - skipping
[WARNING] POM for 'asm:asm:pom:3.1:compile' is invalid.

Its dependencies (if any) will NOT be available to the current build.
[INFO] [exec:java {execution: default-cli}]
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL

[INFO] ------------------------------------------------------------------------ [INFO] Total time: 20 seconds [INFO] Finished at: Fri Jan 04 14:47:33 PST 2013 [INFO] Final Memory: 31M/697M [INFO] ------------------------------------------------------------------------

Where are the logs/outputs? How can I enable logs? Where are the recommendations? Am I doing some thing wrong?

Answer 1

That class you are running is described as "A simple example "runner" class which will evaluate the performance of the current implementation of GroupLensRecommender", which will only give you the "average absolute difference between predicted and actual ratings for users", also known as the "mean average error"

So, you are not really generating recommendations.

Ted Dunning's github account has the Mahout In Action book examples (link). You should have a look.