Understanding Youtube recommender (candidate generation step)












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$begingroup$


I'm trying to understand https://storage.googleapis.com/pub-tools-public-publication-data/pdf/45530.pdf



Their candidate generation step outputs topn items




  • via softmax (with negative sampling) at training time .

  • via nearestneighbor at serving time.


enter image description here





  1. I guess Vj represents, (from softmax layer to nearest neighbor index)

    topn videos you get via softmax, and represent them in the original encoding (same encoding you used for the input (used for embedded video watches))



    apparently, Vj are in the different encoding from the input encodings.
    The softmax layer outputs a multinomial distribution over the same 1M
    video classes with a dimension of 256 (which can be thought
    of as a separate output video embedding)



    I'm trying to understand what they mean by interpreting softmax output as a separate output video embedding. I thought softmax layer that outputs 1M classes has dimension of 1M, where does 256 came from? (It's the same question as How to create a multi-dimensional softmax output in Tensorflow? and I don't think it has been answered there..)



  2. user vector u is the output of the final ReLU unit, although I'm not sure what this user vector is used for.



  3. I guess in serving time, to pick the topn for a given user, user vector u is used by nearest-neighbor. But my understanding of nearest-neighbor is for a given vector, it finds nearest vectors in the same dimension. (such as given an movie, find nearest movies). However here, you are given a user and need to find topn videos. How does that work?



    My best guess is that, for a given user, u get a user vector as the ReLU output, then find user-user nearest neighbor, and combine their topn items obtained in the training time. But it's just a guess..











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    0












    $begingroup$


    I'm trying to understand https://storage.googleapis.com/pub-tools-public-publication-data/pdf/45530.pdf



    Their candidate generation step outputs topn items




    • via softmax (with negative sampling) at training time .

    • via nearestneighbor at serving time.


    enter image description here





    1. I guess Vj represents, (from softmax layer to nearest neighbor index)

      topn videos you get via softmax, and represent them in the original encoding (same encoding you used for the input (used for embedded video watches))



      apparently, Vj are in the different encoding from the input encodings.
      The softmax layer outputs a multinomial distribution over the same 1M
      video classes with a dimension of 256 (which can be thought
      of as a separate output video embedding)



      I'm trying to understand what they mean by interpreting softmax output as a separate output video embedding. I thought softmax layer that outputs 1M classes has dimension of 1M, where does 256 came from? (It's the same question as How to create a multi-dimensional softmax output in Tensorflow? and I don't think it has been answered there..)



    2. user vector u is the output of the final ReLU unit, although I'm not sure what this user vector is used for.



    3. I guess in serving time, to pick the topn for a given user, user vector u is used by nearest-neighbor. But my understanding of nearest-neighbor is for a given vector, it finds nearest vectors in the same dimension. (such as given an movie, find nearest movies). However here, you are given a user and need to find topn videos. How does that work?



      My best guess is that, for a given user, u get a user vector as the ReLU output, then find user-user nearest neighbor, and combine their topn items obtained in the training time. But it's just a guess..











    share







    New contributor




    eugene is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.







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      $begingroup$


      I'm trying to understand https://storage.googleapis.com/pub-tools-public-publication-data/pdf/45530.pdf



      Their candidate generation step outputs topn items




      • via softmax (with negative sampling) at training time .

      • via nearestneighbor at serving time.


      enter image description here





      1. I guess Vj represents, (from softmax layer to nearest neighbor index)

        topn videos you get via softmax, and represent them in the original encoding (same encoding you used for the input (used for embedded video watches))



        apparently, Vj are in the different encoding from the input encodings.
        The softmax layer outputs a multinomial distribution over the same 1M
        video classes with a dimension of 256 (which can be thought
        of as a separate output video embedding)



        I'm trying to understand what they mean by interpreting softmax output as a separate output video embedding. I thought softmax layer that outputs 1M classes has dimension of 1M, where does 256 came from? (It's the same question as How to create a multi-dimensional softmax output in Tensorflow? and I don't think it has been answered there..)



      2. user vector u is the output of the final ReLU unit, although I'm not sure what this user vector is used for.



      3. I guess in serving time, to pick the topn for a given user, user vector u is used by nearest-neighbor. But my understanding of nearest-neighbor is for a given vector, it finds nearest vectors in the same dimension. (such as given an movie, find nearest movies). However here, you are given a user and need to find topn videos. How does that work?



        My best guess is that, for a given user, u get a user vector as the ReLU output, then find user-user nearest neighbor, and combine their topn items obtained in the training time. But it's just a guess..











      share







      New contributor




      eugene is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.







      $endgroup$




      I'm trying to understand https://storage.googleapis.com/pub-tools-public-publication-data/pdf/45530.pdf



      Their candidate generation step outputs topn items




      • via softmax (with negative sampling) at training time .

      • via nearestneighbor at serving time.


      enter image description here





      1. I guess Vj represents, (from softmax layer to nearest neighbor index)

        topn videos you get via softmax, and represent them in the original encoding (same encoding you used for the input (used for embedded video watches))



        apparently, Vj are in the different encoding from the input encodings.
        The softmax layer outputs a multinomial distribution over the same 1M
        video classes with a dimension of 256 (which can be thought
        of as a separate output video embedding)



        I'm trying to understand what they mean by interpreting softmax output as a separate output video embedding. I thought softmax layer that outputs 1M classes has dimension of 1M, where does 256 came from? (It's the same question as How to create a multi-dimensional softmax output in Tensorflow? and I don't think it has been answered there..)



      2. user vector u is the output of the final ReLU unit, although I'm not sure what this user vector is used for.



      3. I guess in serving time, to pick the topn for a given user, user vector u is used by nearest-neighbor. But my understanding of nearest-neighbor is for a given vector, it finds nearest vectors in the same dimension. (such as given an movie, find nearest movies). However here, you are given a user and need to find topn videos. How does that work?



        My best guess is that, for a given user, u get a user vector as the ReLU output, then find user-user nearest neighbor, and combine their topn items obtained in the training time. But it's just a guess..









      deep-learning recommender-system





      share







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      eugene is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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      share







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      Check out our Code of Conduct.








      share



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      eugene is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






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