[GitHub] roywei opened a new issue #12470: foreach operator does not support input's dimension unknown

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

roywei opened a new issue #12470: foreach operator does not support input's dimension unknown
URL: https://github.com/apache/incubator-mxnet/issues/12470
 
 
   ## Description
   In mxnet symbol, None shape is not supported, however we can use 0 as placeholder dimensions.
   See: https://github.com/apache/incubator-mxnet/issues/7981
   we can use
   ```
   x = mx.sym.var('x', shape=(0, 100))
   ```
   instead of 
   ```
   x = mx.sym.var('x', shape=(None, 100))
   ```
   
   But foreach operator will throw error due to check here:
   https://github.com/apache/incubator-mxnet/blob/master/src/operator/control_flow.cc#L317
   
   
   
   ## Error Message:
   ```
   mxnet.base.MXNetError: Error in operator _foreach4: [11:26:26] src/operator/control_flow.cc:317: Check failed: len > 0 (0 vs. 0) 
   Stack trace returned 8 entries:
   [bt] (0) 0   libmxnet.so                         0x0000000102854640 libmxnet.so + 26176
   [bt] (1) 1   libmxnet.so                         0x00000001028543ef libmxnet.so + 25583
   [bt] (2) 2   libmxnet.so                         0x0000000103f61e3f MXTVMBridge + 111375
   [bt] (3) 3   libmxnet.so                         0x0000000103dda022 MXNDListFree + 333138
   [bt] (4) 4   libmxnet.so                         0x0000000103dd240f MXNDListFree + 301375
   [bt] (5) 5   libmxnet.so                         0x0000000103d74a65 MXSymbolInferShape + 2373
   [bt] (6) 6   libmxnet.so                         0x0000000103d77100 MXSymbolInferShapePartial + 112
   [bt] (7) 7   libffi.6.dylib                      0x0000000101fc3884 ffi_call_unix64 + 76
   ```
   
   ## Minimum reproducible example
   ```
   step = lambda data, states: (data + states[0], [states[0] * 2])
   data = mx.sym.var('data', shape=(0,100))
   states = [mx.sym.var('state')]
   outs, states = mx.sym.contrib.foreach(step, data, states)
   outs.infer_shape()
   ```
   ## What have you tried to solve it?
   
   removing [line 317](https://github.com/apache/incubator-mxnet/blob/master/src/operator/control_flow.cc#L317
   ) works, will open a PR.

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