Does bilinear models on vectors mean dot or outer product?












0












$begingroup$


If I have 2 vectors $x$ and $y$ where $x in mathcal{R}^{m}$ and $y in mathcal{R}^{n}$.

Does bilinear model mean?
$f(x,y) = x^TWy$ where $W in mathcal{R}^{m*n}$
which result in a scalar

or
$f(x,y) = W(x⊗y^T)$ where ⊗ is the outer
product and $W in mathcal{R}^{m*n}$.
which result in a matrix



I checked 2 papers, the first one Low-rank Bilinear Pooling
in page 2 in equation 1 their bilinear model produce a scalar

while in Compact Bilinear Pooling in section 3.1 they said "Bilinear models take the outer product of two vectors"










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$endgroup$

















    0












    $begingroup$


    If I have 2 vectors $x$ and $y$ where $x in mathcal{R}^{m}$ and $y in mathcal{R}^{n}$.

    Does bilinear model mean?
    $f(x,y) = x^TWy$ where $W in mathcal{R}^{m*n}$
    which result in a scalar

    or
    $f(x,y) = W(x⊗y^T)$ where ⊗ is the outer
    product and $W in mathcal{R}^{m*n}$.
    which result in a matrix



    I checked 2 papers, the first one Low-rank Bilinear Pooling
    in page 2 in equation 1 their bilinear model produce a scalar

    while in Compact Bilinear Pooling in section 3.1 they said "Bilinear models take the outer product of two vectors"










    share|cite|improve this question









    $endgroup$















      0












      0








      0





      $begingroup$


      If I have 2 vectors $x$ and $y$ where $x in mathcal{R}^{m}$ and $y in mathcal{R}^{n}$.

      Does bilinear model mean?
      $f(x,y) = x^TWy$ where $W in mathcal{R}^{m*n}$
      which result in a scalar

      or
      $f(x,y) = W(x⊗y^T)$ where ⊗ is the outer
      product and $W in mathcal{R}^{m*n}$.
      which result in a matrix



      I checked 2 papers, the first one Low-rank Bilinear Pooling
      in page 2 in equation 1 their bilinear model produce a scalar

      while in Compact Bilinear Pooling in section 3.1 they said "Bilinear models take the outer product of two vectors"










      share|cite|improve this question









      $endgroup$




      If I have 2 vectors $x$ and $y$ where $x in mathcal{R}^{m}$ and $y in mathcal{R}^{n}$.

      Does bilinear model mean?
      $f(x,y) = x^TWy$ where $W in mathcal{R}^{m*n}$
      which result in a scalar

      or
      $f(x,y) = W(x⊗y^T)$ where ⊗ is the outer
      product and $W in mathcal{R}^{m*n}$.
      which result in a matrix



      I checked 2 papers, the first one Low-rank Bilinear Pooling
      in page 2 in equation 1 their bilinear model produce a scalar

      while in Compact Bilinear Pooling in section 3.1 they said "Bilinear models take the outer product of two vectors"







      linear-algebra matrices






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      share|cite|improve this question











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      share|cite|improve this question










      asked Dec 19 '18 at 11:53









      floydfloyd

      1032




      1032






















          1 Answer
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          1












          $begingroup$

          "Bilinear" is simply an adjective that you can apply to any function of two vectors to indicate that it is linear in each argument. So the linear map



          $(x,y) rightarrow x^TWy$



          and the tensor product



          $(x,y) rightarrow xy^T$



          can both be described as bilinear, even though their codomains are different.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            What about the element-wise product between 2 vectors? The reason I mention it is because it's different than the dot and outer product because it's doesn't take into account all the interactions between the 2 vectors (like what the dot product does).
            $endgroup$
            – floyd
            Jan 7 at 20:20











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          1 Answer
          1






          active

          oldest

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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          1












          $begingroup$

          "Bilinear" is simply an adjective that you can apply to any function of two vectors to indicate that it is linear in each argument. So the linear map



          $(x,y) rightarrow x^TWy$



          and the tensor product



          $(x,y) rightarrow xy^T$



          can both be described as bilinear, even though their codomains are different.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            What about the element-wise product between 2 vectors? The reason I mention it is because it's different than the dot and outer product because it's doesn't take into account all the interactions between the 2 vectors (like what the dot product does).
            $endgroup$
            – floyd
            Jan 7 at 20:20
















          1












          $begingroup$

          "Bilinear" is simply an adjective that you can apply to any function of two vectors to indicate that it is linear in each argument. So the linear map



          $(x,y) rightarrow x^TWy$



          and the tensor product



          $(x,y) rightarrow xy^T$



          can both be described as bilinear, even though their codomains are different.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            What about the element-wise product between 2 vectors? The reason I mention it is because it's different than the dot and outer product because it's doesn't take into account all the interactions between the 2 vectors (like what the dot product does).
            $endgroup$
            – floyd
            Jan 7 at 20:20














          1












          1








          1





          $begingroup$

          "Bilinear" is simply an adjective that you can apply to any function of two vectors to indicate that it is linear in each argument. So the linear map



          $(x,y) rightarrow x^TWy$



          and the tensor product



          $(x,y) rightarrow xy^T$



          can both be described as bilinear, even though their codomains are different.






          share|cite|improve this answer









          $endgroup$



          "Bilinear" is simply an adjective that you can apply to any function of two vectors to indicate that it is linear in each argument. So the linear map



          $(x,y) rightarrow x^TWy$



          and the tensor product



          $(x,y) rightarrow xy^T$



          can both be described as bilinear, even though their codomains are different.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Dec 19 '18 at 12:16









          gandalf61gandalf61

          8,826725




          8,826725












          • $begingroup$
            What about the element-wise product between 2 vectors? The reason I mention it is because it's different than the dot and outer product because it's doesn't take into account all the interactions between the 2 vectors (like what the dot product does).
            $endgroup$
            – floyd
            Jan 7 at 20:20


















          • $begingroup$
            What about the element-wise product between 2 vectors? The reason I mention it is because it's different than the dot and outer product because it's doesn't take into account all the interactions between the 2 vectors (like what the dot product does).
            $endgroup$
            – floyd
            Jan 7 at 20:20
















          $begingroup$
          What about the element-wise product between 2 vectors? The reason I mention it is because it's different than the dot and outer product because it's doesn't take into account all the interactions between the 2 vectors (like what the dot product does).
          $endgroup$
          – floyd
          Jan 7 at 20:20




          $begingroup$
          What about the element-wise product between 2 vectors? The reason I mention it is because it's different than the dot and outer product because it's doesn't take into account all the interactions between the 2 vectors (like what the dot product does).
          $endgroup$
          – floyd
          Jan 7 at 20:20


















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