[GitHub] [incubator-mxnet] samskalicky opened a new issue #15296: Graph Executor does not track mutable input dependencies

[GitBox <gi...@apache.org>]

samskalicky opened a new issue #15296: Graph Executor does not track mutable input dependencies
URL: https://github.com/apache/incubator-mxnet/issues/15296
 
 
   ## Description
   In the Symbol/Module flow, the graph executor does not track mutable input dependencies when setting up the use_vars and mutate_vars arrays here:
   https://github.com/apache/incubator-mxnet/blob/master/src/executor/graph_executor.cc#L1222-L1234
   
   Notice that inputs are only added to use_vars on line 1224, and mutate_vars only contains outputs. 
   
   Compare this to the CachedOp flow in Gluon where we get the mutable inputs here:
   https://github.com/apache/incubator-mxnet/blob/master/src/imperative/imperative_utils.h#L245
   
   and then add all mutable inputs to the write_vars array on line 294 (here read_vars is the same as use_vars, and write_vars is the same as mutate_vars in the graph executor above). 
   
   This means that its possible that write dependencies would not be tracked correctly in the symbol/module flows for operators that use the FMutateInputs attribute. Currently it looks like only BatchNorm uses this. 
   
   ## Test case
   This can be tested using BatchNorm, by creating a symbol graph that only contains batch norm and run with the same running mean and variance many times

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