{"action":"opened","issue":{"url":"https://api.github.com/repos/torch/nn/issues/944","repository_url":"https://api.github.com/repos/torch/nn","labels_url":"https://api.github.com/repos/torch/nn/issues/944/labels{/name}","comments_url":"https://api.github.com/repos/torch/nn/issues/944/comments","events_url":"https://api.github.com/repos/torch/nn/issues/944/events","html_url":"https://github.com/torch/nn/issues/944","id":173735973,"number":944,"title":"Difference between MaxPooling and SubSampling","user":{"login":"dolaameng","id":36718,"avatar_url":"https://avatars.githubusercontent.com/u/36718?v=3","gravatar_id":"","url":"https://api.github.com/users/dolaameng","html_url":"https://github.com/dolaameng","followers_url":"https://api.github.com/users/dolaameng/followers","following_url":"https://api.github.com/users/dolaameng/following{/other_user}","gists_url":"https://api.github.com/users/dolaameng/gists{/gist_id}","starred_url":"https://api.github.com/users/dolaameng/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/dolaameng/subscriptions","organizations_url":"https://api.github.com/users/dolaameng/orgs","repos_url":"https://api.github.com/users/dolaameng/repos","events_url":"https://api.github.com/users/dolaameng/events{/privacy}","received_events_url":"https://api.github.com/users/dolaameng/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":0,"created_at":"2016-08-29T09:41:04Z","updated_at":"2016-08-29T09:41:04Z","closed_at":null,"body":"Forgive me if I am asking an naive question. What is the difference between Pooling and Sampling, say [TemporalMaxPooling](https://github.com/torch/nn/blob/master/doc/convolution.md#temporalmaxpooling) vs [TemporalSubSampling](https://github.com/torch/nn/blob/master/doc/convolution.md#temporalsubsampling), and [SpatialMaxPooling](https://github.com/torch/nn/blob/master/doc/convolution.md#spatialmaxpooling) and [SpatialSubSampling](https://github.com/torch/nn/blob/master/doc/convolution.md#spatialsubsampling)?  \r\n\r\nMy understanding is that both of them are layer-wise operations (as special cases of convolution?), where each layer of the input will be mapped independently to a layer of the output. With the difference that a `MaxPooling` use a max op and `SubSampling` use a `Weighted sum of the local region`. \r\n\r\nSo is it safe to say that `SubSampling` is a generalization of `MaxPooling` and `AveragePooling`? Is there any references on how to use `SubSampling` in practice?\r\n\r\nThe documentations on both [TemporalSubSampling](https://github.com/torch/nn/blob/master/doc/convolution.md#temporalsubsampling) and  [SpatialSubSampling](https://github.com/torch/nn/blob/master/doc/convolution.md#spatialsubsampling) are a little confusing. E.g.,\r\n- In TemporalSubSampling Section, it says \"If the input sequence is a 2D tensor `nInputFrame x inputFrameSize`, the output sequence will be `inputFrameSize x nOutputFrame`\", should it be `nOutputFrame x inputFrameSize` based on the definition equation below or I misunderstood it?\r\n- Similar as in SpatialSubSampling section, where it says \"the output image size will be `nInputPlane x oheight x owidth`\", but in the equation below `output[i][j][k] = bias[k] + weight[k] sum_{s=1}^kW sum_{t=1}^kH input[dW*(i-1)+s)][dH*(j-1)+t][k]`, the order of the input and output dimension is actually `owidth x oheight x nInputPlane`.\r\n\r\nAppreciate it if someone can help. "}}
{"actor":{"display_login":"dolaameng"}}