[Feature] Base/Row alignment support for Tensors

[zacharyvincze]

PR Description

General

• Adds padding (row/base pointer alignment) support for roccv::Tensor.
• Adds MemAlign class which is used as a parameter when allocating memory for Tensors. This specifies what the row alignment and base alignment should be for newly created tensors.

Samples

• Changes support reading/writing images from host <-> device with tensor padding in mind.
• Improves help messages and command line argument parsing across all samples.

Tensors

• Stride calculation logic changed to take non-contiguous data (row padding) into account.
• Reshape method implementation changed to take into account non-contiguous tensors. Ensures that the shape cannot be changed across the row padding boundary, as this is supposed to be a zero-copy operation which retains the initial memory layout.
• Quality of life methods for checking whether a tensor is contiguous, and for returning the amount of non-padded (non-garbage) bytes being used by the tensor.
• Adds copyToHost and copyFromHost methods to the tensor, which accepts and produces contiguous host buffers. Since padding makes copying memory from the host to the device non-trivial, this allows the user to perform a copy which is agnostic to the underlying row padding that a tensor may have.

Python bindings (rocpycv)

• Adds correctness changes to DLPack conversion. Checks whether strides are provided by DLPack first, if so, uses them directly after converting from element-wise to byte-wise strides, otherwise, assumes a contiguous tensor is being provided by DLPack and recalculates with that assumption.

Tests

• Helpers which copy from host to device now use Tensor::copyFromHost, Tensor::copyToHost directly instead of using duplicate code.
• Adds Tensor unit tests to ensure padding is calculated properly, and that any additional methods added to roccv::Tensor are covered. Special attention is paid to the reshape method, since this has undergone the most changes.

[simonCatBot]

Review: [Feature] Base/Row alignment support for Tensors

Major feature addition for Tensor memory layout:

Key additions:

• MemAlign class for memory allocation control
• Row/base pointer alignment support
• Non-contiguous tensor handling with proper stride calculations
• copyToHost/copyFromHost for padded tensor handling
• Updated reshape logic respecting padding boundaries
• DLPack stride conversion fixes
• Comprehensive unit tests

Assessment: Needs Review - Large architectural change.

This is a substantial PR (+2010/-1165 lines across 24 files) that changes core tensor semantics. The approach looks solid - explicit handling of padding makes the API clearer. Questions for maintainers:

1. Backward compatibility with existing code?
2. Performance impact of stride calculations?
3. Memory overhead of the alignment system?

Well documented and includes tests. Ready for deep review.

[Copilot]

Pull request overview

This PR adds base-pointer and per-row alignment (padding) support to roccv::Tensor, updating stride/reshape semantics and introducing host<->device copy helpers that are padding-aware. It also updates samples, Python bindings, benchmarks, and tests to operate correctly with non-contiguous (row-padded) tensors.

Changes:

• Introduce MemAlignment and update Tensor allocation/stride/reshape logic to support row/base alignment and non-contiguous layouts.
• Add Tensor::copyFromHost / Tensor::copyToHost and refactor tests/helpers/samples to use padding-aware copies.
• Update Python DLPack import to honor provided strides (and convert element-strides to byte-strides), with a contiguous fallback.

Reviewed changes

Copilot reviewed 24 out of 24 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
src/core/tensor.cpp	Core implementation updates: alignment-aware stride calc, reshape for non-contiguous tensors, host copy helpers.
include/core/tensor.hpp	Public API updates for alignment-aware construction + new copy/contiguity helpers.
include/core/mem_alignment.hpp / src/core/mem_alignment.cpp	New alignment configuration type used during tensor allocation.
include/core/utils.hpp	New low-level helpers (power-of-two + align-up) used for alignment/stride logic.
src/core/tensor_storage.cpp / include/core/tensor_storage.hpp	Expose allocator used by TensorStorage.
src/op_non_max_suppression.cpp	Update reshape call sites to new reshape(dtype, shape) signature.
python/src/py_tensor.cpp / python/include/py_tensor.hpp	DLPack import correctness fixes + documentation/typing cleanup.
tests/roccv/cpp/src/tests/core/tensor/test_tensor.cpp	Add/adjust tensor tests for padding/reshape/copy helpers.
tests/roccv/cpp/include/test_helpers.hpp	Refactor host<->device copy helpers to use new tensor copy APIs.
samples/common/utils.hpp	Add batch image load/write utilities that respect tensor padding.
samples/*.cpp (multiple)	Update CLI parsing + use new image IO helpers (padding-aware).
benchmarks/src/roccv/roccv_bench_helpers.cpp	Update benchmark filling logic to account for padded allocation sizes.

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 77.87234% with 52 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/core/tensor.cpp	76.47%	33 Missing and 15 partials ⚠️
include/core/utils.hpp	78.57%	3 Missing ⚠️
src/core/tensor_storage.cpp	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #136      +/-   ##
===========================================
+ Coverage    73.88%   73.97%   +0.09%     
===========================================
  Files           77       80       +3     
  Lines         2998     3189     +191     
  Branches       645      683      +38     
===========================================
+ Hits          2215     2359     +144     
- Misses         339      373      +34     
- Partials       444      457      +13     

Files with missing lines	Coverage Δ
include/core/mem_alignment.hpp	100.00% <100.00%> (ø)
include/core/tensor.hpp	62.50% <ø> (ø)
src/core/mem_alignment.cpp	100.00% <100.00%> (ø)
src/op_non_max_suppression.cpp	41.18% <100.00%> (ø)
src/core/tensor_storage.cpp	81.48% <0.00%> (-3.13%)	⬇️
include/core/utils.hpp	78.57% <78.57%> (ø)
src/core/tensor.cpp	72.53% <76.47%> (+1.23%)	⬆️

... and 1 file with indirect coverage changes

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