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Add fbgemm_utils lookup helper libraries for XPU training operators#81

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aagalleg wants to merge 30 commits into
intel:mainfrom
aagalleg:feat/add_lookup_utils
Draft

Add fbgemm_utils lookup helper libraries for XPU training operators#81
aagalleg wants to merge 30 commits into
intel:mainfrom
aagalleg:feat/add_lookup_utils

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@aagalleg

@aagalleg aagalleg commented Jul 3, 2026

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This PR adds the supporting utility headers and source files under
fbgemm_utils/ that are required by the forward and backward embedding
lookup kernels on Intel XPU devices.

Depends on #80

Changes

Core Utilities (src/fbgemm_xpu/fbgemm_utils/)

  • vec4.h: Vec4T<T> template struct for 4-element vectorized
    memory access backed by a sycl::float4 accumulator. Includes
    template specializations for float and at::Half with optimized
    load/store operations, round-to-nearest-even half-precision
    conversion matching CUDA semantics, and a vec4_acc helper for
    element-wise accumulation. Vec4TAcc<T> alias wraps the accumulator
    type via at::acc_type

  • stochastic_rounding.h: Lightweight 64-bit xorshift* RNG
    (StochasticRoundingRNGState) seeded from Philox state for generating
    random bits, plus stochastic_rounding_scalar and
    stochastic_rounding_vector template specializations for float-to-half
    conversion with stochastic rounding to reduce quantization bias

  • weight_row.h: WeightRow<emb_t, cache_t, reg_t> template
    class abstracting load/store access to embedding table rows with
    transparent cache/device switching, optional stochastic rounding on
    stores, and an optimizer_state_ptr<T>() method for accessing
    optimizer state packed at a 4-element-aligned offset within the row.
    Includes a read-only WeightRowAccessor variant and a pad4 utility
    for computing aligned offsets

  • feature_gates.h/cpp: Runtime feature flag system backed by
    FBGEMM_* environment variables. Provides is_feature_enabled(),
    is_feature_enabled_from_env(), and check_feature_gate_key() with
    an in-process cache to avoid repeated env-var lookups

  • pt2_arg_utils.h: Named index enumerations
    (ArgIndex_aux_tensor, ArgIndex_aux_bool, ArgIndex_aux_int,
    ArgIndex_aux_float) for accessing the auxiliary argument arrays used
    in PT2-compiled embedding operators, replacing numbers with
    descriptive constants

  • split_embeddings_cache_xpu.h: uvm_cache_stats_index enum
    defining named indices into the UVM cache statistics tensor
    (num_calls, num_requested_indices, num_unique_misses, etc.)

cc: @flezaalv

aagalleg and others added 30 commits June 18, 2026 22:37
- Add invert_permute kernel to CMake build
- Implement invert_permute Python wrapper in ops.py
- Register invert_permute operator with schema existence check
- Add torch_library.h utility for schema validation
Add SYCL/XPU kernel implementation for invert_permute operation.
Add complete test coverage for invert_permute operator on XPU
devices, covering correctness, validation, parity, and performance.

Test coverage includes:
- Correctness tests for int32/int64 with edge cases (empty, single
  element, identity, reverse, random permutations)
- Input validation tests for invalid dimensions and dtypes
- Meta function tests for torch.compile compatibility
- PyTorch opcheck validation for operator conventions
- Parametric tests with varying sizes (1 to 1M elements)
- CPU-XPU parity tests to ensure consistent results
- Performance benchmarks measuring execution time and bandwidth
- CMakeLists: add permute_1d_sparse_data.cpp to build sources
- ops.py: add Python wrapper with type hints
- ops_registry.cpp: register operator schema in fbgemm namespace
Implement SYCL/XPU kernel implementation of permute_1D_sparse_data
operator for sparse jagged/1D format data permutation.
Add SYCL port of FBGEMM's asynchronous_complete_cumsum operator for
Intel XPU devices. The operator computes a complete cumulative sum
with a leading zero (e.g., [a, b, c] → [0, a, a+b, a+b+c]).
Integrate asynchronous_complete_cumsum operator into fbgemm-xpu:
- Add Python wrapper with complete cumsum documentation
- Register operator schema in torch library
- Include implementation in CMake build
Add comprehensive test suite for asynchronous_complete_cumsum
operator covering:
- Basic functionality with int32 and int64 dtypes
- Empty tensor handling
- Random input validation with numpy reference
Add SYCL infrastructure headers from intel/torch-xpu-ops/
to support advanced kernel implementations:
- DeviceProperties.h: Device capability queries and work group sizing
- SYCLContext.h: SYCL context management and namespace aliases
- SYCLHelpers.h: SYCL kernel submission and utility functions
- TensorInfo.h: Tensor metadata and dimension handling structures
- TensorOptions.h: Tensor configuration and options management
- Runtime.h: SYCL runtime utilities
- Macros.h: Common macro definitions
- Scalar.h: Scalar type conversion utilities

These headers provide the foundation for implementing 2D sparse data
permutation and other complex SYCL operations on XPU devices.
Add foundational utility headers and implementations to support
complex SYCL kernel operations:
- utils.h/cpp: Core constants, type definitions, kernel launch
  helpers, and device property queries
- dispatch_macros.h: Type dispatch macros for handling multiple
  data types (int32, int64, float, etc.)
- tensor_utils.h: Tensor manipulation and metadata utilities
- function_types.h: Symbol visibility definitions for shared
  library exports

These utilities provide essential infrastructure for implementing
2D sparse data permutation and other advanced operators on XPU
devices, including work group sizing, kernel launch helpers, and
type-safe dispatching mechanisms.
Add SYCL port of FBGEMM's permute_2D_sparse_data operator for
Intel XPU devices. This operator permutes 2D sparse data including
lengths [T, B], indices, and optional weights according to a
permutation vector, commonly used for reordering embedding table
features.

Implementation includes:
- SYCL kernels: permute_2D_lengths_kernel and permute_2D_data_kernel
- Host function: permute_2D_sparse_data_xpu
Integrate permute_2D_sparse_data operator into fbgemm-xpu:
- Add Python wrapper with type hints and documentation
- Register operator schema in torch library
- Include implementation files in CMake build (utils.cpp, SYCL
  kernels, and operator implementation)
Add comprehensive test suite for permute_2D_sparse_data operator
covering:
- Basic functionality with int32 and int64 data types
- Sparse data with and without weights
- Permutations with repeated indices
- Exact value validation
- CPU-XPU consistency verification
Fixes CMake configuration and import ordering to properly build and load
the block_bucketize_sparse_features XPU operator.

- Configure CMake for XPU-only PyTorch builds
- Import torch before _C extension to load libtorch.so dependencies
- Adjust test imports for consistency

All 18 tests passing.
… generation

Add jinja_environment.py module to support template-based code
generation for FBGEMM-XPU kernels.
Add common.py module with CodeTemplate class that provides
functionality for loading Jinja2 templates, rendering them with
context variables, and writing generated files with appropriate
headers.
Add torch_type_utils.py module with utilities for handling PyTorch
data types in template-based code generation.
Add generate_forward_split.py and generate_backward_split.py scripts
for generating SYCL embedding kernels from Jinja2 templates.
Add backward_utils.cpp and backward_utils.h with SYCL ports of
FBGEMM backward pass utilities for embedding operations.
…mization

Add vec4.h header implementing 4-element vectorized data structures
for efficient memory access in embedding operations.
Add feature_gates module to enable/disable features at runtime via environment variables.
Add pt2_arg_utils.h header defining argument index enumerations for
PyTorch 2 compiled embedding operations.
Add split_embeddings_cache_xpu.h header defining indices for UVM
(Unified Virtual Memory) cache performance statistics.
…version

Add stochastic_rounding.h header implementing stochastic rounding
algorithms for float-to-half precision conversions in embedding
operations.
Add weight_row.h header implementing abstractions for efficient
access to embedding table weight rows with support for both direct
table access and cache-resident data.
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