[FFI] Adopt PackedFunc on Numpy Imperative Invoke

[barry-jin]

Description

Adopt PackedFunc based FFI on imperative invoke to reduce overhead.

Checklist

Essentials

• PR's title starts with a category (e.g. [BUGFIX], [MODEL], [TUTORIAL], [FEATURE], [DOC], etc)
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage
• Code is well-documented

Changes

• Feature1, tests, (and when applicable, API doc)
• Feature2, tests, (and when applicable, API doc)

Comments

• If this change is a backward incompatible change, why must this change be made.
• Interesting edge cases to note here

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[barry-jin]

@mxnet-bot run ci [all]

[mxnet-bot]

Jenkins CI successfully triggered : [centos-cpu, miscellaneous, centos-gpu, windows-gpu, unix-gpu, sanity, clang, edge, website, windows-cpu, unix-cpu]

[leezu]

Adopt PackedFunc based FFI on imperative invoke to reduce overhead.

Have you measured the improvement for this PR? Previously I thought you intend to convert the remaining operators to the new FFI, rendering the generic imperative invoke unneeded?

[barry-jin]

Adopt PackedFunc based FFI on imperative invoke to reduce overhead.

Have you measured the improvement for this PR? Previously I thought you intend to convert the remaining operators to the new FFI, rendering the generic imperative invoke unneeded?

Yes, some operators that takes no stringified params as invocation input will benefit a bit from it.
copyto

setup = """
from mxnet import np, npx
npx.set_np()
a = np.zeros((2,2))
b = np.ones((2,2))
"""
stmt = """
c = a.copyto(b)
"""
timer = timeit.Timer(setup=setup,
                     stmt=stmt)
num_repeat = 1000
print(min(timer.repeat(repeat=10, number=num_repeat)) / num_repeat)

legacy
5.821948400000032e-05
New FFI
5.494140500000011e-05

npx.gather_nd

setup = """
from mxnet import np, npx
npx.set_np()
a = np.zeros((2,2))
b = np.ones((2,2))
"""
stmt = """
c = npx.gather_nd(a, b)
"""
timer = timeit.Timer(setup=setup,
                     stmt=stmt)
num_repeat = 1000
print(min(timer.repeat(repeat=10, number=num_repeat)) / num_repeat)

legacy
8.739984900000009e-05
New FFI
7.992273099999991e-05