[GitHub] fhieber opened a new issue #13862: [Bug] unravel_index no longer works with magic '-1' in shape parameter after 1.3.1

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

fhieber opened a new issue #13862: [Bug] unravel_index no longer works with magic '-1' in shape parameter after 1.3.1
URL: https://github.com/apache/incubator-mxnet/issues/13862
 
 
   ## Description
   The `unravel_index` op seems to no longer correctly work with 'magic' shape values, such as '-1's. The following example still works with mxnet 1.3.1, but does not on latest master (it returns all zeros in the result without throwing an error). I don't know when this was introduced, whether its present in the 1.4 rc or was changed later.
   We have a [use case](https://github.com/awslabs/sockeye/blob/master/sockeye/inference.py#L2100) for this in Sockeye.
   
   ## Environment info (Required)
   macOs
   
   MXNet commit hash:
   pip-installed:
   mxnet                    1.5.0b20190111
   
   ## Minimum reproducible example
   Input data taken from Sockete unit tests.
   ```python
   x = mx.nd.array([335, 620, 593, 219, 36], dtype='int32')
   mx.nd.unravel_index(x, shape=(-1, 200))
   ```
   With mxnet==1.5.0b20190111, the result is incorrect:
   ```python
   [[  0   0   0   0   0]
    [135  20 193  19  36]]
   <NDArray 2x5 @cpu(0)>
   ```
   
   With mxnet==1.3.1, the result is correct:
   ```python
   [[  1   3   2   1   0]
    [135  20 193  19  36]]
   <NDArray 2x5 @cpu(0)>
   ```
   
   However, if the shape parameter is fully specified (`shape=(5,200)`), `mxnet==1.5.0b20190111` returns the correct values.
   

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