reminisce commented on issue #8029: Bug on sum URL: https://github.com/apache/incubator-mxnet/issues/8029#issuecomment-332393859 @tqchen It was found that the control_deps of a gradient node is the gradient node itself. For a graph like this: `sym = data + data`, where `data` is a symbolic variable, the node entries in `vector<NodeEntry> v` have the same node of op `_identity_with_attr_like_rhs` (same node ptr). https://github.com/apache/incubator-mxnet/blob/master/src/executor/graph_executor.cc#L204 Therefore, the assumption that `v[i-1]` does not depend on `v[i]` is not valid here and a cycle is introduced into the gradient graph. @piiswrong suggested checking with you to see if we could skip adding control deps for a node if `v[i-1]` and `v[i]` are the same. I checked the commit history, and it shows that you added [this line](https://github.com/apache/incubator-mxnet/blob/master/src/executor/graph_executor.cc#L204) for resolving this issue: https://github.com/apache/incubator-mxnet/pull/4093. Thank you for your help. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected]
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