{"action":"opened","issue":{"url":"https://api.github.com/repos/tensorflow/tensorflow/issues/6455","repository_url":"https://api.github.com/repos/tensorflow/tensorflow","labels_url":"https://api.github.com/repos/tensorflow/tensorflow/issues/6455/labels{/name}","comments_url":"https://api.github.com/repos/tensorflow/tensorflow/issues/6455/comments","events_url":"https://api.github.com/repos/tensorflow/tensorflow/issues/6455/events","html_url":"https://github.com/tensorflow/tensorflow/issues/6455","id":197132749,"number":6455,"title":"gradient for tf.gather_nd","user":{"login":"nina124","id":6497205,"avatar_url":"https://avatars.githubusercontent.com/u/6497205?v=3","gravatar_id":"","url":"https://api.github.com/users/nina124","html_url":"https://github.com/nina124","followers_url":"https://api.github.com/users/nina124/followers","following_url":"https://api.github.com/users/nina124/following{/other_user}","gists_url":"https://api.github.com/users/nina124/gists{/gist_id}","starred_url":"https://api.github.com/users/nina124/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/nina124/subscriptions","organizations_url":"https://api.github.com/users/nina124/orgs","repos_url":"https://api.github.com/users/nina124/repos","events_url":"https://api.github.com/users/nina124/events{/privacy}","received_events_url":"https://api.github.com/users/nina124/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":0,"created_at":"2016-12-22T09:41:06Z","updated_at":"2016-12-22T09:41:06Z","closed_at":null,"body":"I use tf.gather_nd to build a Value Iteration Block(NIPS2016 best paper, value iteration network). \r\nI need to pick several \"pixels\" (the input (i,j) in the following picture) in the feature map Q_n.\r\n![image](https://cloud.githubusercontent.com/assets/6497205/21421213/a8e6a8be-c86c-11e6-8801-714ca47c4c2f.png)\r\n\r\n\r\nBut I got this error: NotImplementedError: Gradient for gather_nd is not implemented.\r\nI know gradient for tf.gather is implemented, but tf.gather could only slice the first dimentsion. It should be easy to transfer the gradient of tf.gather to tf.gather_nd.\r\nOr anyone could tell me how to implement this operation and train this?"}}
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