I have found several tutorials on how to create my own non-distributed recommender but none how to create my own distributed recommender job (any link is welcome if you know one).
In the book “Mahout in Action” there are some examples of how to write Mappers/Reducers using Mahout’s objects, but it does not seem to show how to put these jobs together?
However there is item/RecommenderJob in mahout-core which gives an idea of how this can be done. My actual intent is to replace the first mapper so that I don’t have to prepare my data outside of mahout (lines look like “userid,itemid1,itemid2,itemid3…” and using item.RecommenderJob I obviously need lines like “itemid1,itemid2”, “itemid1,itemid3”, …).
Now would it be a good idea to just copy over the RecommenderJob class and change what I need?
I have tried it, but since this class uses variables that are in package scope (e. g. UserVectorSplitterMapper.USERS_FILE) I have to replace these – which does not feel good.
Should I rather create a new class extending AbstractJob and pick out the things I need from RecommenderJob? Then what are the elements in RecommenderJob that I really need?
Your alternatives are to precede the job with your own job that translates your input into a form the job wants, or, indeed to just modify the job. I don’t think it’s a big deal to copy the job and modify and customize it if you need non-trivial changes that aren’t (and wouldn’t make sense to be) supported as some kind of config parameter.