Thanks for the replies Sebastian and Sean. I looked at the similarity values and they are the same, but ItemSimilarityJob is calculating fewer of them. So it must be still doing some sort of sampling. I thought that I could force it to use all of the data by setting maxPrefsPerUser sufficiently large. Could there be another reason for it not to calculate all of the similarity values?
I also tried to use a smaller amount of similarItemsPerItem but this leads to worse results. Thanks again, Greg
