# Source code for mars.tensor.indexing.flatnonzero

#!/usr/bin/env python
# -*- coding: utf-8 -*-
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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
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# http://www.apache.org/licenses/LICENSE-2.0
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from .nonzero import nonzero
[docs]def flatnonzero(a):
"""
Return indices that are non-zero in the flattened version of a.
This is equivalent to a.ravel().nonzero()[0].
Parameters
----------
a : Tensor
Input tensor.
Returns
-------
res : Tensor
Output tensor, containing the indices of the elements of `a.ravel()`
that are non-zero.
See Also
--------
nonzero : Return the indices of the non-zero elements of the input tensor.
ravel : Return a 1-D tensor containing the elements of the input tensor.
Examples
--------
>>> import mars.tensor as mt
>>> x = mt.arange(-2, 3)
>>> x.execute()
array([-2, -1, 0, 1, 2])
>>> mt.flatnonzero(x).execute()
array([0, 1, 3, 4])
Use the indices of the non-zero elements as an index array to extract
these elements:
>>> x.ravel()[mt.flatnonzero(x)].execute() # TODO(jisheng): accomplish this after fancy indexing is supported
"""
from ..base import ravel
return nonzero(ravel(a))[0]