I am doing some research on building recommendation engine.
One problem I found in Chapter 5 BUILDING COLLABORATIVE FILTERING RECOMMENDATION ENGINES is the sample code in python doing recommendation on Movie Lens 100k data is that the RMSE values are as high as 11.
A quick google can find some tutorials on the web, doing the same thing on ml-100k data set, using SVD or ALS algorithm have a RMSE lower than 1.0, commonly 0.9x.
In the Chapter 7 of the book, BUILDING REAL-TIME RECOMMENDATION ENGINES WITH SPARK, author using Spark ALS reached 0.9x RMSE on same data set.
It looks the author did not put too much effort polishing Chapter 5’s code sample.
I would recommend following articles and samples over Chapter 5 of this book: