[RFC]: add native float32 support for ML loss functions and activation primitives #16124

Description

This RFC proposes adding native single-precision (float32) support for the core machine learning loss functions and activation primitives.

Currently, the lack of float32 packages forces the engine to cast Float32Array buffers up to float64 to compute mathematical operations before casting back down. This doubles memory bandwidth usage and hinders SIMD vectorization. These proposed packages rely on standard algebraic arithmetic and can be efficiently implemented via single-precision C kernels without requiring new polynomial derivations.

Core ML Loss Functions (Forward & Gradients)

• ml/base/loss/float32/epsilon-insensitive
• ml/base/loss/float32/epsilon-insensitive-gradient
• ml/base/loss/float32/hinge
• ml/base/loss/float32/hinge-gradient feat: add ml/base/loss/float32/hinge-gradient #16275
• ml/base/loss/float32/huber
• ml/base/loss/float32/huber-gradient feat: add ml/base/loss/float32/huber-gradient #16289
• ml/base/loss/float32/log
• ml/base/loss/float32/log-gradient
• ml/base/loss/float32/modified-huber
• ml/base/loss/float32/modified-huber-gradient
• ml/base/loss/float32/squared-epsilon-insensitive
• ml/base/loss/float32/squared-epsilon-insensitive-gradient
• ml/base/loss/float32/squared-error
• ml/base/loss/float32/squared-error-gradient feat: add ml/base/loss/float32/squared-error-gradient #16287
• ml/base/loss/float32/squared-hinge
• ml/base/loss/float32/squared-hinge-gradient feat: add ml/base/loss/float32/squared-hinge-gradient #16276

ML Activations

• math/base/special/siluf
• math/base/special/geluf
• math/base/special/fast/gelu-tanhf
• math/base/special/fast/gelu-quickf

Prerequisites

The above ML pipeline relies on the following core single-precision math primitives, which are already being tracked in the #649:

• math/base/special/erfcf (Required for geluf)
• math/base/special/expitf (Required for siluf and gelu-tanhf)
• math/base/special/log1pexpf (Required for log loss functions)

Related Issues

None.

Questions

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Other

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Checklist

• I have read and understood the Code of Conduct.
• Searched for existing issues and pull requests.
• The issue name begins with RFC:.