Add npx op 'index_add'

[JiangZhaoh]

Description

Forward for index_add.

Checklist

Essentials

Please feel free to remove inapplicable items for your PR.

• The PR title starts with [MXNET-$JIRA_ID], where $JIRA_ID refers to the relevant JIRA issue created (except PRs with tiny changes)
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage:
• Unit tests are added for small changes to verify correctness (e.g. adding a new operator)
• Nightly tests are added for complicated/long-running ones (e.g. changing distributed kvstore)
• Build tests will be added for build configuration changes (e.g. adding a new build option with NCCL)
• Code is well-documented:
• For user-facing API changes, API doc string has been updated.
• For new C++ functions in header files, their functionalities and arguments are documented.
• For new examples, README.md is added to explain the what the example does, the source of the dataset, expected performance on test set and reference to the original paper if applicable
• Check the API doc at https://mxnet-ci-doc.s3-accelerate.dualstack.amazonaws.com/PR-$PR_ID/$BUILD_ID/index.html
• To the best of my knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change

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

[mxnet-bot]

Hey @JiangZhaoh , Thanks for submitting the PR
All tests are already queued to run once. If tests fail, you can trigger one or more tests again with the following commands:

• To trigger all jobs: @mxnet-bot run ci [all]
• To trigger specific jobs: @mxnet-bot run ci [job1, job2]

---

CI supported jobs: [website, centos-gpu, centos-cpu, sanity, windows-cpu, unix-cpu, unix-gpu, windows-gpu, clang, edge, miscellaneous]

---

Note:
Only following 3 categories can trigger CI :PR Author, MXNet Committer, Jenkins Admin.
All CI tests must pass before the PR can be merged.

[sxjscience]

Is it using the new FFI?

[zheyuye]

Related to #17823

[zheyuye]

It seems that this operation currently only supports floating type. In addition, it would be great if the data types of indices can be extended to np.ndarray instead of only tuple and list as

import mxnet as mx
a = mx.np.zeros((2,6))
val = mx.np.arange(6)
x = [1,0,0,0,0,0]
y = [0,2,3,4,0,1]
# indices = [list, list]
mx.npx.index_add(a, val, [x, y])
# indices = (list, list)
mx.npx.index_add(a, val, (x, y))
# indices = [np.ndarray, np.ndarray]
x = mx.np.array(x).astype('int32')
y = mx.np.array(y).astype('int32')
mx.npx.index_add(a, val, [x, y])

>>> MXNetError: MXNetError: Invalid Parameter format for ind expect tuple of <Shape(tuple)> 
but value='[array([1, 0, 0, 0, 0, 0], dtype=int32), array([0, 2, 3, 4, 0, 1], dtype=int32)]', in 
operator _npx_index_add(name="", ind="[array([1, 0, 0, 0, 0, 0], dtype=int32), array([0, 2, 3, 4, 0, 1], dtype=int32)]")

[JiangZhaoh]

For npx.index_add(a, ind, val), now it supports int32 or int64 tensor ind, and both int or float tensor a and val. But it requires the dtype of a and val keep same.

[sxjscience]

LGTM overall. Needs to fix the CudaMalloc + cudaFree.

[JiangZhaoh]

@mxnet-bot run ci [unix-gpu, windows-cpu, windows-gpu]

[mxnet-bot]

Jenkins CI successfully triggered : [windows-cpu, windows-gpu, unix-gpu]

[JiangZhaoh]

@mxnet-bot run ci [unix-gpu, unix-cpu, centos-gpu]

[mxnet-bot]

Jenkins CI successfully triggered : [unix-cpu, unix-gpu, centos-gpu]

[sxjscience]

@yzhliu I've suggested @JiangZhaoh to write the gradient op by reusing the forward op. This has multiple benefits:

1. We can do more optimization in the graph pass
2. It's easy to support higher-order gradient.

I think we may add the document about such usage since not many people are aware of that.

[sxjscience]

@mxnet-bot run ci [centos-gpu] [unix-cpu] [unix-gpu] [windows-cpu] [windows-gpu]

[mxnet-bot]

Jenkins CI successfully triggered : [centos-gpu]

[leezu]

@mxnet-bot run ci [unix-cpu, unix-gpu, windows-cpu, windows-gpu]

[mxnet-bot]

Jenkins CI successfully triggered : [unix-cpu, windows-gpu, windows-cpu, unix-gpu]

[sxjscience]

Thanks @JiangZhaoh , this is merged.