dpctl.tensor.where output preserves memory order of inputs

[ndgrigorian]

This PR adjusts the behavior of dpctl.tensor.where to preserve the memory layout of its inputs. This improves the access pattern of the kernel.

Performance of old behavior:

In [1]: import dpctl.tensor as dpt, numpy as np

In [2]: dt = dpt.int32

In [3]: sh = (8160, 8160)

In [4]: ar1 = dpt.ones(sh, dtype=dt, order="C")[:4080, ::-2].mT

In [5]: ar2 = dpt.zeros(sh, dtype=dt, order="C")[:4080, ::-2].mT

In [6]: condition = dpt.zeros(sh, dtype=dt, order="C")[:4080, ::-2].mT

In [7]: res = dpt.where(condition, ar1, ar2)
CPU times: user 143 ms, sys: 53.4 ms, total: 196 ms
Wall time: 220 ms

In [8]: %time res = dpt.where(condition, ar1, ar2)
CPU times: user 48.3 ms, sys: 67.6 ms, total: 116 ms
Wall time: 119 ms

In [9]: %time res = dpt.where(condition, ar1, ar2)
CPU times: user 81.5 ms, sys: 31.1 ms, total: 113 ms
Wall time: 114 ms

New behavior:

In [9]: %time res = dpt.where(condition, ar1, ar2)
CPU times: user 26.9 ms, sys: 198 µs, total: 27.1 ms
Wall time: 27.8 ms

In [10]: %time res = dpt.where(condition, ar1, ar2)
CPU times: user 16.1 ms, sys: 13.8 ms, total: 29.9 ms
Wall time: 30.9 ms

In [11]: %time res = dpt.where(condition, ar1, ar2)
CPU times: user 23.3 ms, sys: 1.43 ms, total: 24.7 ms
Wall time: 26.7 ms

which is an improvement of ~4x in certain cases.

_empty_like_triple_orderK is introduced for this purpose and a test was added to ensure that the output strides are as expected.

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• Have you added a test, reproducer or referred to an issue with a reproducer?
• Have you tested your changes locally for CPU and GPU devices?
• Have you made sure that new changes do not introduce compiler warnings?
• Have you checked performance impact of proposed changes?
• If this PR is a work in progress, are you opening the PR as a draft?

[github-actions]

View rendered docs @ https://intelpython.github.io/dpctl/pulls/1342/index.html

[coveralls]

coverage: 85.072% (+0.03%) from 85.041% when pulling 873b0b6 on where-order-K into bd996b5 on master.

[github-actions]

Array API standard conformance tests for dpctl=0.14.6dev2=py310h7bf5fec_5 ran successfully.
Passed: 913
Failed: 87
Skipped: 119

[github-actions]

Array API standard conformance tests for dpctl=0.14.6dev3=py310ha25a700_22 ran successfully.
Passed: 913
Failed: 87
Skipped: 119

[github-actions]

Array API standard conformance tests for dpctl=0.14.6dev3=py310ha25a700_23 ran successfully.
Passed: 913
Failed: 87
Skipped: 119

[oleksandr-pavlyk]

I think this looks good to go in @ndgrigorian. I had a small nitpick, but it just a matter of style.

[github-actions]

Array API standard conformance tests for dpctl=0.14.6dev3=py310ha25a700_24 ran successfully.
Passed: 913
Failed: 87
Skipped: 119

[github-actions]

Deleted rendered PR docs from intelpython.github.com/dpctl, latest should be updated shortly. 🤞

[github-actions]

Array API standard conformance tests for dpctl=0.14.6dev3=py310ha25a700_43 ran successfully.
Passed: 913
Failed: 87
Skipped: 119