GitHub user gaborhermann opened a pull request:
https://github.com/apache/flink/pull/2542
[FLINK-4613] Extend ALS to handle implicit feedback datasets
This extension of the ALS algorithm changes some parts of the code if
`implicitPrefs` flag is set to true. Mainly the local parts parts are changed:
the `Xt * X` computation takes into consideration the confidence, thus
computing `Xt * (C - I) * X` instead (see the paper by Hu et al. for details).
The `Xt * X` matrix is precomputed and broadcasted, and that is the only thing
that affects distributed execution.
Note, that we use a temporary directory in the test, because there would
not be enough memory segments to perform a hash join for prediction. I assume
that memory segments are not freed up after the training if no temporary
directory is set, but I did not investigate the issue as using a tempdir is a
simple workaround.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/gaborhermann/flink ials
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/flink/pull/2542.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #2542
----
commit 84d338b11f77b20fa1825029f8ca847a40eb4673
Author: Gábor Hermann <c...@gaborhermann.com>
Date: 2016-09-12T09:47:40Z
[FLINK-4613] Compute XtX for IALS & test, docs
commit 8e7c0d67a6f0390f03765fcdc9e03f3c391807cd
Author: jfeher <feh...@gmail.com>
Date: 2016-09-12T09:57:44Z
[FLINK-4613] Extend ALS for implicit case
XtX matrix precomputation is not yet done.
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