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Posted to issues@mxnet.apache.org by GitBox <gi...@apache.org> on 2022/03/18 05:29:13 UTC
[GitHub] [incubator-mxnet] DickJC123 opened a new issue #20968: mxnet.numpy and original numpy differ on bitwise right shift of uint64 types
DickJC123 opened a new issue #20968:
URL: https://github.com/apache/incubator-mxnet/issues/20968
## Description
This difference was flagged by the array api tests, so it's likely that mxnet.numpy is not producing the correct value. Test failure log is: https://jenkins.mxnet-ci.com/blue/organizations/jenkins/mxnet-validation%2Funix-cpu/detail/PR-20957/3/pipeline/286/#step-438-log-636
When mxnet.numpy does a right shift on a uint64 type, if uses a low level instruction that duplicates the most significant bit (i.e. an arithmetic right shift). The simplest example showing the issue involves a right shift by 1 of 2**63 (a value with just the most significant bit set):
```
$python
>>> import mxnet.numpy as mxnp
>>> import numpy as np
>>> 2**63
9223372036854775808
>>> bin(2**63)
'0b1000000000000000000000000000000000000000000000000000000000000000'
>>> 2**63 >> 1
4611686018427387904
>>> np.right_shift(np.array(2**63, dtype='uint64'), np.array(1, dtype='uint8'))
4611686018427387904
>>> mxnp.bitwise_right_shift(mxnp.array(2**63, dtype='uint64'), mxnp.array(1, dtype='uint8'))
array(13835058055282163712, dtype=uint64)
>>> bin(13835058055282163712)
'0b1100000000000000000000000000000000000000000000000000000000000000'
```
A recent issue I filed involving an array api unittest failure involved Cython vs. ctypes, but this issue is unrelated and most likely an issue with the cast to int64_t in the lines:
https://github.com/apache/incubator-mxnet/blob/master/src/operator/mshadow_op.h#L835-L847
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[GitHub] [incubator-mxnet] agrabows commented on issue #20968: mxnet.numpy and original numpy differ on bitwise right shift of uint64 types
Posted by GitBox <gi...@apache.org>.
agrabows commented on issue #20968:
URL: https://github.com/apache/incubator-mxnet/issues/20968#issuecomment-1075402289
Hi, I added a fix here: https://github.com/apache/incubator-mxnet/pull/20974. It was caused by static_cast to int64.
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