Unary Kernel Design

The unary runtime adapters implement Abs, Exp, Log, and Not. Their node-specific classes live under onnx_light_cpu/kernels/math and onnx_light_cpu/kernels/logical; typed compute functions and tuning helpers live under onnx_light_cpu/impl.

Execution architecture

Each registered adapter follows the same path:

NodeProto + RuntimeContext
           |
           v
     KernelBase::Run
           |
           v
   validate type and shape
           |
           v
   resolve immutable tuning
           |
           v
scalar/SIMD range function
           |
           v
   session CpuExecutor

The output retains the input shape and type. Run allocates it through the runtime context, while the direct operator() entry points require matching preallocated input and output tensors.

Operators and types

Operator	Registered types	Implementation
Abs	FLOAT, DOUBLE, FLOAT16, BFLOAT16, INT8, INT16, INT32, INT64	Typed scalar fallbacks and ISA-selected vector loops, including low-precision and integer paths.
Exp / Log	FLOAT, DOUBLE, FLOAT16, BFLOAT16	Shared scheduling with operator-specific approximation, conversion, exceptional-value, and tail handling.
Not	BOOL	Byte-valued boolean inversion; ONNX BOOL tensors are not bit-packed.

Tuning and scheduling

unary_execution_tuning.h contains the shared range schedulers. ExecuteUnaryRanges uses a byte threshold for inexpensive operations, while ExecuteCostedUnaryRanges also accounts for the operation cost. The resolved tuning snapshot contains the bulk threshold, target block size, and participant limit; Abs can additionally select preferred participants and a streaming-store threshold.

Small tensors execute on the calling thread. Setting the parallel threshold to zero disables executor dispatch completely. Otherwise, larger tensors are divided into independent contiguous ranges and submitted to onnx-light’s current CpuExecutor. A participant limit of zero means that the session executor may use every participant it admits.

Dispatch and invariants

ISA selection is cached and gated by both compiled translation units and runtime CPU capabilities. Unsupported instructions are never entered on a weaker host, and every vector implementation has an exact scalar tail and a portable fallback.

The adapters reject unsupported types and mismatched buffers before compute. Floating-point paths preserve their documented NaN, infinity, signed-zero, and domain behavior; integer absolute value avoids undefined signed overflow.