# Copyright 2022-2023 XProbe Inc.
# derived from copyright 1999-2021 Alibaba Group Holding Ltd.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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from ..datasource import tensor as astensor
[docs]def flip(m, axis):
"""
Reverse the order of elements in a tensor along the given axis.
The shape of the array is preserved, but the elements are reordered.
Parameters
----------
m : array_like
Input tensor.
axis : integer
Axis in tensor, which entries are reversed.
Returns
-------
out : array_like
A view of `m` with the entries of axis reversed. Since a view is
returned, this operation is done in constant time.
See Also
--------
flipud : Flip a tensor vertically (axis=0).
fliplr : Flip a tensor horizontally (axis=1).
Notes
-----
flip(m, 0) is equivalent to flipud(m).
flip(m, 1) is equivalent to fliplr(m).
flip(m, n) corresponds to ``m[...,::-1,...]`` with ``::-1`` at position n.
Examples
--------
>>> import mars.tensor as mt
>>> A = mt.arange(8).reshape((2,2,2))
>>> A.execute()
array([[[0, 1],
[2, 3]],
[[4, 5],
[6, 7]]])
>>> mt.flip(A, 0).execute()
array([[[4, 5],
[6, 7]],
[[0, 1],
[2, 3]]])
>>> mt.flip(A, 1).execute()
array([[[2, 3],
[0, 1]],
[[6, 7],
[4, 5]]])
>>> A = mt.random.randn(3,4,5)
>>> mt.all(mt.flip(A,2) == A[:,:,::-1,...]).execute()
True
"""
m = astensor(m)
sl = [slice(None)] * m.ndim
try:
sl[axis] = slice(None, None, -1)
except IndexError:
raise ValueError(
"axis=%i is invalid for the %i-dimensional input tensor" % (axis, m.ndim)
)
return m[tuple(sl)]