Hello spark users and developers, I read the paper from Yahoo about CF with implicit feedback and other papers using implicit feedbacks. Their implementation require to set the missing rating with 0. That is for unobserved ratings, the confidence for those is set to 1 (c=1). Therefore, the matrix to be factorized is a dense matrix.
I read the source code of the ALS implementation in spark (version 1.6.x) for implicit feedback. Apparently, it ignores rating that is 0 (Line 1159 in ALS.scala). It could be a mistake or it could be an optimization. Just want to see if anyone steps on this yet. Best Regards, Jerry
