Implement advanced indexing (boolean mask, integer array) in mohu-index

[Bbn08]

Summary

mohu-index handles indexing strategies beyond basic slicing. Implement boolean mask indexing and integer array (fancy) indexing -- the two most common advanced indexing patterns.

API surface

// crates/mohu-index/src/lib.rs
pub fn index_bool(src: &Buffer, mask: &Buffer) -> MohuResult<Buffer>;
pub fn index_take(src: &Buffer, indices: &Buffer, axis: usize) -> MohuResult<Buffer>;

Behavior

index_bool (boolean mask):

• mask dtype must be DType::Bool; otherwise DomainError
• mask must have same shape as src; otherwise ShapeMismatch
• Returns 1D buffer of elements where mask is true

index_take (integer array indexing):

• indices dtype must be DType::I64; otherwise DomainError
• Selects elements along axis at positions given by indices
• Out-of-bounds index returns MohuError::IndexOutOfBounds
• Negative indices not supported in v1 (return IndexOutOfBounds)

Acceptance criteria

• index_bool extracts correct elements for 1D and 2D mask
• index_take gathers correct rows/cols for 1D and 2D src
• All error cases tested
• Output is always a new owning buffer (no view aliasing)
• No .unwrap() in library code

Signed-off-by: Bbn08 atrancendentbeing@gmail.com

[Akanksha-2712]

Hi @Bbn08 ,

I would like to work on this issue for GSSoC.

I have understood the requirements clearly:

• Implement index_bool with strict dtype (Bool) and shape validation
• Return flattened 1D owning buffer containing only true masked elements
• Implement index_take for integer array indexing using I64 indices
• Handle axis-based gathering for both 1D and 2D buffers
• Add proper error handling for invalid dtype, shape mismatch, negative indices, and out-of-bounds access
• Ensure no view aliasing and avoid .unwrap() usage in library code
• Add comprehensive unit tests for success and failure cases

Please assign this issue to me.

[Akanksha-2712]

@Bbn08 Thank you for assigning it to me !!

[abdulamaan29]

assign

[rajesh-puripanda]

Hi @Akanksha-2712, just checking whether this issue is currently being worked on actively.

I’d be interested in contributing to this if there’s no ongoing implementation or PR planned yet. Happy to wait if progress is already underway.

@Bbn08 please consider me in case reassignment becomes possible. Thanks!

[rajesh-puripanda]

/assign gssoc

[github-actions]

Assigned to @rajesh-puripanda ✓

[github-actions]

Assigned to @Pcmhacker-piro ✓

[sakshiwankhade026-coder]

/assign gsssoc
I would like to contribute to this project under gssoc and would love to work on this issue. I have experience working on open-source contributions and would be happy to implement the required changes.

Could you please assign this issue to me? Thanks!

[github-actions]

Assigned to @sakshiwankhade026-coder ✓

[rajesh-puripanda]

Quick update — I was assigned this advanced indexing issue 14 days ago. I'm working on the implementation and expect to have a PR ready shortly. Appreciate your patience.