1x1 convolutions, equivalence with fully connected layer












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I'm confused by the concept of equating a 1x1 convolution with a fully connected layer. Take the following simple example of a 1x1 convolution of 2 input channels each of size 2x2, and a single output channel.



enter image description here



The only way I can relate this to fully connected layers is to say that there are 4 fully connected layers, one for each location in the input feature map (inputs and outputs colour coded).



From what I can understand my interpretation is consistent with the Network in Network paper[Lin et al. 2013] which describe the 1x1 as being equivalent as cross channel parametric pooling




The cross channel parametric pooling layer is also equivalent to a
convolution layer with 1x1 con- volution kernel.




I have seen
this one from Yann LeCunn equating 1x1 convolutions to a fully connected layer. And I have read this answer and I'm just not seeing the equivalence between a 1x1 convolution over an input volume and a single fully connected layer...



Any insight would be appreciated, if you can please relate back to the example above. Thanks!










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    2












    $begingroup$


    I'm confused by the concept of equating a 1x1 convolution with a fully connected layer. Take the following simple example of a 1x1 convolution of 2 input channels each of size 2x2, and a single output channel.



    enter image description here



    The only way I can relate this to fully connected layers is to say that there are 4 fully connected layers, one for each location in the input feature map (inputs and outputs colour coded).



    From what I can understand my interpretation is consistent with the Network in Network paper[Lin et al. 2013] which describe the 1x1 as being equivalent as cross channel parametric pooling




    The cross channel parametric pooling layer is also equivalent to a
    convolution layer with 1x1 con- volution kernel.




    I have seen
    this one from Yann LeCunn equating 1x1 convolutions to a fully connected layer. And I have read this answer and I'm just not seeing the equivalence between a 1x1 convolution over an input volume and a single fully connected layer...



    Any insight would be appreciated, if you can please relate back to the example above. Thanks!










    share|improve this question







    New contributor




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







    $endgroup$















      2












      2








      2


      1



      $begingroup$


      I'm confused by the concept of equating a 1x1 convolution with a fully connected layer. Take the following simple example of a 1x1 convolution of 2 input channels each of size 2x2, and a single output channel.



      enter image description here



      The only way I can relate this to fully connected layers is to say that there are 4 fully connected layers, one for each location in the input feature map (inputs and outputs colour coded).



      From what I can understand my interpretation is consistent with the Network in Network paper[Lin et al. 2013] which describe the 1x1 as being equivalent as cross channel parametric pooling




      The cross channel parametric pooling layer is also equivalent to a
      convolution layer with 1x1 con- volution kernel.




      I have seen
      this one from Yann LeCunn equating 1x1 convolutions to a fully connected layer. And I have read this answer and I'm just not seeing the equivalence between a 1x1 convolution over an input volume and a single fully connected layer...



      Any insight would be appreciated, if you can please relate back to the example above. Thanks!










      share|improve this question







      New contributor




      nixon 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 confused by the concept of equating a 1x1 convolution with a fully connected layer. Take the following simple example of a 1x1 convolution of 2 input channels each of size 2x2, and a single output channel.



      enter image description here



      The only way I can relate this to fully connected layers is to say that there are 4 fully connected layers, one for each location in the input feature map (inputs and outputs colour coded).



      From what I can understand my interpretation is consistent with the Network in Network paper[Lin et al. 2013] which describe the 1x1 as being equivalent as cross channel parametric pooling




      The cross channel parametric pooling layer is also equivalent to a
      convolution layer with 1x1 con- volution kernel.




      I have seen
      this one from Yann LeCunn equating 1x1 convolutions to a fully connected layer. And I have read this answer and I'm just not seeing the equivalence between a 1x1 convolution over an input volume and a single fully connected layer...



      Any insight would be appreciated, if you can please relate back to the example above. Thanks!







      neural-network convnet






      share|improve this question







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      nixon is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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      share|improve this question







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      asked 18 hours ago









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