nx_f32_activations.nx

nx_f32_activations.nx -- bits-up f32 ML activation functions. L7 composition brick. Composes L4 mul/add/sub/div + L6 exp. Provides sigmoid, SiLU/Swish, tanh -- the standard activation set used in Llama / Mistral / Qwen / GPT-class transformers. All functions: scalar f32 in, scalar f32 out. Caller broadcasts across tensor elements. No libm. Sigmoid: sigma(x) = 1 / (1 + exp(-x)) Endpoints: x -> +inf : 1.0 x -> -inf : +0 Our exp clamps very-negative-arg to 0 -> sigma -> 1, and very-positive-arg to +inf -> sigma -> 0. Both extreme cases handled correctly without underflow path. SiLU / Swish: silu(x) = x * sigma(x) Used as the gate activation in Llama FFN SwiGLU. Hendrycks+Gimpel 2016 (GELU); Ramachandran+ 2017 (Swish); Elfwing+ 2017 (SiLU). Tanh: tanh(x) = 2 * sigma(2x) - 1 Cheaper than the canonical (exp(x)-exp(-x))/(exp(x)+exp(-x)) form via the sigmoid identity.