Posts tagged data science
Posts tagged data science
The Million Song Dataset Challenge is a contest hosted on Kaggle. Its goal is to predict the songs that 100,000 users will listen to, given their listening history and additional listening histories and data about the songs.
Predicting held-out past user choices is a proxy for another task that cannot be directly evaluated without using a live system: personalized recommendation.
MyMediaLite is a tool/library containing state-of-the-art recommendation algorithms. In this post, I explain how MyMediaLite can be used to make predictions for the Million Song Dataset Challenge.
First, you need to install MyMediaLite. Don’t worry, it is quite easy, and should work fine on Linux, Mac OS X, and Windows.
You will also need several gigabytes of disk space, the challenge datasets, and a working Unix-like environment. On Linux and Mac this should not be a problem. For Windows you could use Cygwin to get such an environment.
In the following, I assume that you have installed MyMediaLite 3.01 (it must be the latest version, because only that one contains some features we will make use of) in
~/src/MyMediaLite. If it is somewhere else, just adapt the paths below accordingly.
In the MyMediaLite directory, create a directory
data/millionsong, and put the unzipped competition dataset there.
cat kaggle_users.txt | perl -ne 'chomp; print "$_\t" . ++$l . "\n"' > user_id_mappings.txt cut -f 2 user_id_mappings.txt > test_users.txt cut -f 2 -d ' ' kaggle_songs.txt > candidate_items.txt # create dataset ~/src/MyMediaLite/scripts/import_dataset.pl --load-user-mapping=user_id_mappings.txt --load-item-mapping=kaggle_songs.txt kaggle_visible_evaluation_triplets.txt > msd.train.txt # create CV splits mkdir cv ~/src/MyMediaLite/scripts/per_user_crossvalidation.pl --k=5 --filename=cv/msd < msd.train.txt # use one split for validation cp cv/msd-0.train.txt msd_validation.train.txt cp cv/msd-0.test.txt msd_validation.test.txt mkdir validation_predictions mkdir validation_submissions # prepare directories for prediction/submission files and logs mkdir logs mkdir submissions mkdir predictions
Trying out Different Recommenders
Run in the MyMediaLite directory:
bin/item_recommendation --training-file=msd_validation.train.txt --test-file=msd_validation.test.txt --data-dir=data/millionsong --recommender=MostPopular --random-seed=1 --predict-items-number=500 --num-test-users=1000 --no-id-mapping --candidate-items=candidate_items.txt
You will get an output like this:
Set random seed to 1. loading_time 1.67 memory 21 training data: 110000 users, 149052 items, 1160746 events, sparsity 99.99292 test data: 110000 users, 77330 items, 290187 events, sparsity 99.99659 MostPopular training_time 00:00:00.0718350 .AUC 0.56605 prec@5 0.0078 prec@10 0.007 MAP 0.02051 recall@5 0.01875 recall@10 0.03011 NDCG 0.05008 MRR 0.02324 num_users 1000 num_items 386213 num_lists 1000 testing_time 00:00:35.3801840 memory 120
The MAP 0.02051 is the interesting piece of information: This is an estimate of how well we will perform on the leaderboard with this recommender.
The command for the WRMF recommender is similar, only that we also see results at different iterations:
k=28; cpos=28; reg=0.002; bin/item_recommendation --training-file=msd_validation.train.txt --test-file=msd_validation.test.txt --recommender=WRMF --random-seed=1 --predict-items-number=500 --num-test-users=1000 --test-users=test_users.txt --find-iter=1 --max-iter=30 --recommender-options="num_iter=0 num_factors=$k c_pos=$cpos reg=$reg" --data-dir=data/millionsong --no-id-mapping --candidate-items=candidate_items.txt
The output will be like this (I removed some parts for better readability):
WRMF num_factors=28 regularization=0.002 c_pos=28 num_iter=0 MAP 0.00003 iteration 0 MAP 0.01106 iteration 1 MAP 0.01659 iteration 2 MAP 0.02593 iteration 3 MAP 0.03558 iteration 4 ... MAP 0.05341 iteration 30
Nice. This is already some improvement over the MostPopular baseline.
Creating a Submission
bin/item_recommendation --training-file=data/millionsong/msd.train.txt --recommender=MostPopular --predict-items-number=500 --prediction-file=data/millionsong/predictions/mp.pred --test-users=data/millionsong/kaggle_users.txt
k=28; cpos=28; reg=0.002; it=30; bin/item_recommendation --training-file=msd.train.txt --recommender=WRMF --random-seed=1 --predict-items-number=500 --recommender-options="num_iter=$it num_factors=$k c_pos=$cpos reg=$reg" --prediction-file=predictions/wrmf-k-$k-cpos-$cpos-reg-$reg-it-$it.pred --test-users=kaggle_users.txt --candidate-items=candidate_items.txt --data-dir=data/millionsong
MyMediaLite’s output format is a bit different from the submission file format, so I wrote a little script to convert the prediction file:
~/src/MyMediaLite/scripts/msdchallenge/create_submission.sh < predictions/wrmf-k-28-cpos-28-reg-0.002-it-30.pred > submissions/wrmf-k-28-cpos-28-reg-0.002-it-30.sub ~/src/MyMediaLite/scripts/msdchallenge/create_submission.sh < predictions/mp.pred > submissions/mp.sub
It will not hurt to make sure the submission file is in the correct format (using the script provided by the organizers) before trying to upload it:
Compress before upload:
Now you can upload the submission files to Kaggle. I got the following results:
I am currently preparing three further blog posts, which I will publish during the next days (links will be provided when the post are ready):
The approach demonstrated here is just a simple one, relying on functions that are already available in MyMediaLite. One can think of many extensions, either using existing functionality, or implementing them using the framework provided by MyMediaLite:
Want to learn more about MyMediaLite?
Rebranding of statistics as a field seems to be a popular topic these days and “data science” is one of the potential rebranding options. This article over at Revolutions is a nice summary of where the term comes from and what it means. This quote seems pretty accurate:
My own take is that Data Science is a valuable rebranding of computer science and applied statistics skills.