Activation.hpp File Reference

Public activation enum and helpers for FlexNN. More...

#include <cstdint>
#include <string_view>
#include <type_traits>
#include <Eigen/Dense>
#include "ActivationParameters.hpp"

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Namespaces
namespace	FlexNN
	Namespace for the FlexNN neural network library.
namespace	FlexNN::Activations
namespace	FlexNN::Activations::detail

Enumerations
enum class	FlexNN::Activations::Activation : uint8_t {   FlexNN::Activations::None = 0 , FlexNN::Activations::ReLU = 1 , FlexNN::Activations::LeakyReLU = 2 , FlexNN::Activations::Sigmoid = 3 ,   FlexNN::Activations::Tanh = 4 , FlexNN::Activations::Softmax = 5 }
	Activation function identifier. More...

Functions
const char *	FlexNN::Activations::to_string (Activation a) noexcept
	Convert Activation to canonical lower-case string.
bool	FlexNN::Activations::try_parse (std::string_view s, Activation &out) noexcept
	Parse a string into an Activation.
Eigen::MatrixXd	FlexNN::Activations::detail::forward (Activation act, const Eigen::MatrixXd &Z, const ActivationParameters &params=ActivationParameters{})
	Elementwise forward for a single activation.
Eigen::MatrixXd	FlexNN::Activations::detail::backward (Activation act, const Eigen::MatrixXd &dA, const Eigen::MatrixXd &Z, const Eigen::MatrixXd &A, const ActivationParameters &params=ActivationParameters{}) noexcept
	Elementwise backward for a single activation (hidden layers).
Eigen::MatrixXd	FlexNN::Activations::detail::softmax_forward (const Eigen::MatrixXd &Z)
	Stable column-wise softmax forward.
Eigen::MatrixXd	FlexNN::Activations::detail::softmax_backward_hidden (const Eigen::MatrixXd &s, const Eigen::MatrixXd &upstream) noexcept
	Softmax hidden backward: dZ = J * upstream per column.

Detailed Description

Public activation enum and helpers for FlexNN.

Defines the type-safe FlexNN::Activations::Activation enum that replaces the old stringly-typed std::string activationFunction. The enum is 1 byte (uint8_t) so it maps directly to the model.bin flat binary (see LLD_FLEXNN §7 / Appendix A). Per-activation elementwise ops live in include/activations (e.g., ReLU.hpp) and are re-exported via FlexNN::Activations::detail for use by lib/layers.

Why this file exists:

• Gives -Wswitch-enum exhaustiveness: adding a new Activation forces updates to every switch without a default branch.
• No heap, no linear string compare in hot forward path.
• Keeps the public enum separate from the per-activation math so tests can include a single header (Activation.hpp) without pulling all per-activation headers unless needed.