The random ranking is assigned after every `pio train` so if you have not
trained in-between, they will be the same. Random is not really meant to do
what you are using it for, it is meant to surface items with no data—no
primary events. This will allow some to get real events and be recommended
for the events next time you train. It is meant to fill in when you ask for
20 recs but there are only 10 things to be recommended. Proper use of this
with frequent training will cause items with no data to be purchased and to
therefore get data. The reason rankings are assigned at train time is that
this is the only way to get all of the business rules applied to the query
as well as a random ranking. In other words the ranking must be built into
the model with `pio train`
If you want to recommend random items each time you query, create a list of
item ids from your catalog and return some random sample each query
yourself. This should be nearly trivial.
From: Brian Chiu
Reply: user@predictionio.apache.org
Date: August 28, 2018 at 1:51:24 AM
To: u...@predictionio.incubator.apache.org
Subject: Distinct recommendation from "random" backfill?
Dear pio developers and users:
I have been using predictionIO and Universal Recommender for a while.
In universal recommender engiene.json, there is a configuration field
`rankings`, and one of the option is random. Initially I thought it
would give each item without any related event some random recommended
items, and each of the recommendation list is different. However, it
turns out all of the random recommended item list is the same. For
example, if both item "6825991" and item "682599" have no events
during training, the result will be
```
$ curl -H "Content-Type: application/json" -d '{ "item": "6825991" }'
http://localhost:8000/queries.json
{"itemScores":[{"item":"8083748","score":0.0},{"item":"7942100","score":0.0},{"item":"8016271","score":0.0},{"item":"7731061","score":0.0},{"item":"8002458","score":0.0},{"item":"7763317","score":0.0},{"item":"8141119","score":0.0},{"item":"8080694","score":0.0},{"item":"7994844","score":0.0},{"item":"7951667","score":0.0},{"item":"7948453","score":0.0},{"item":"8148479","score":0.0},{"item":"8113083","score":0.0},{"item":"8041124","score":0.0},{"item":"8004823","score":0.0},{"item":"8126058","score":0.0},{"item":"8093042","score":0.0},{"item":"8064036","score":0.0},{"item":"8022524","score":0.0},{"item":"7977131","score":0.0}]}
$ curl -H "Content-Type: application/json" -d '{ "item": "682599" }'
http://localhost:8000/queries.json
{"itemScores":[{"item":"8083748","score":0.0},{"item":"7942100","score":0.0},{"item":"8016271","score":0.0},{"item":"7731061","score":0.0},{"item":"8002458","score":0.0},{"item":"7763317","score":0.0},{"item":"8141119","score":0.0},{"item":"8080694","score":0.0},{"item":"7994844","score":0.0},{"item":"7951667","score":0.0},{"item":"7948453","score":0.0},{"item":"8148479","score":0.0},{"item":"8113083","score":0.0},{"item":"8041124","score":0.0},{"item":"8004823","score":0.0},{"item":"8126058","score":0.0},{"item":"8093042","score":0.0},{"item":"8064036","score":0.0},{"item":"8022524","score":0.0},{"item":"7977131","score":0.0}]}
```
But I my webpage, whenever user click on these products without
events, they will see exactly the same recommended items, making it
looks boring. Is there anyway to give each item distinct random list?
Even if it is generated dynamically is OK. If you have any other
alternative, please also tell me.
Thanks all developers!
Best Regards,
Brian
