CF toolkit: Use rankUpdate() to calculate XtX in ALS and WALS #24
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added 5 commits
April 29, 2014 18:10
Conflicts: toolkits/collaborative_filtering/als_tensor.cpp
last_item_bias file is saved with .mm extension, but loaded with .m
This optimized calculation gives around a 2X speedup on the small netflix set in my testing (D=20)
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Two changes, first is a typo fix, libFM writes the item_bias factor with the file extension ".mm" but tries to read it with extension ".m".
The second change is to use rankUpdate when computing XtX in the ALS and weighted ALS implementation. The function rankUpdate() provides an optimized way to compute M += alpha(uu*), which is exactly what we want.
In some simple testing on the small Netflix data I was seeing runtimes cut in half with this change.