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Date: Wed, 28 Jun 2017 19:29:00 +0000 (UTC)
From: "Mike Dusenberry (JIRA)" <jira@apache.org>
To: issues@systemml.apache.org
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Subject: [jira] [Closed] (SYSTEMML-1736) Add new 2D top_k utility function
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archived-at: Wed, 28 Jun 2017 19:29:05 -0000


     [ https://issues.apache.org/jira/browse/SYSTEMML-1736?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Mike Dusenberry closed SYSTEMML-1736.
-------------------------------------

> Add new 2D top_k utility function
> ---------------------------------
>
>                 Key: SYSTEMML-1736
>                 URL: https://issues.apache.org/jira/browse/SYSTEMML-1736
>             Project: SystemML
>          Issue Type: Sub-task
>            Reporter: Mike Dusenberry
>            Assignee: Fei Hu
>             Fix For: SystemML 1.0
>
>
> We should add a new {{top_k2d}} utility function (in {{nn/util.dml}}) that accepts a matrix {{X}} and return matrices {{values}} and {{indices}} with the top {{k}} values (i.e. probabilities) and associated indices (i.e. classes) along a certain dimension.  This will be modeled after the [{{top_k}} function in TensorFlow | https://www.tensorflow.org/api_docs/python/tf/nn/top_k].  For the 2D case, {{top_k}} will operate on the channels dimension.  A typical use case here is that in which {{X}} is the output of a {{softmax2d}} layer (so each channel contains a set of normalized class probabilities), and {{values}} and {{indices}} will contain the top {{k}} probabilities and indices along the channel axis.  This scenario would be common in an image segmentation problem, in which every pixel of the output image will have a set of class probabilities along the channel axis.
> Having these {{top-k}} functions will allow us to extract either predict a single class for each item, or the top {{k}} classes, and therefore may be more useful that a {{predict_class}} function.
> Although we will use {{values}} and {{indices}} as the names of the returned matrices within the functions, in practice, one is likely to name the results {{probs}} and {{classes}} in the calling environment.


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