Source code for activations

"""
Has the built-in activation functions,
code for using them,
and code for adding new user-defined ones
"""
from __future__ import division
import math
import types


def sigmoid_activation(z):
    z = max(-60.0, min(60.0, 5.0 * z))
    return 1.0 / (1.0 + math.exp(-z))


def tanh_activation(z):
    z = max(-60.0, min(60.0, 2.5 * z))
    return math.tanh(z)


def sin_activation(z):
    z = max(-60.0, min(60.0, 5.0 * z))
    return math.sin(z)


def gauss_activation(z):
    z = max(-3.4, min(3.4, z))
    return math.exp(-5.0 * z ** 2)


def relu_activation(z):
    return z if z > 0.0 else 0.0


def elu_activation(z):
    return z if z > 0.0 else math.exp(z) - 1


def lelu_activation(z):
    leaky = 0.005
    return z if z > 0.0 else leaky * z


def selu_activation(z):
    lam = 1.0507009873554804934193349852946
    alpha = 1.6732632423543772848170429916717
    return lam * z if z > 0.0 else lam * alpha * (math.exp(z) - 1)


def softplus_activation(z):
    z = max(-60.0, min(60.0, 5.0 * z))
    return 0.2 * math.log(1 + math.exp(z))


def identity_activation(z):
    return z


def clamped_activation(z):
    return max(-1.0, min(1.0, z))


def inv_activation(z):
    try:
        z = 1.0 / z
    except ArithmeticError:  # handle overflows
        return 0.0
    else:
        return z


def log_activation(z):
    z = max(1e-7, z)
    return math.log(z)


def exp_activation(z):
    z = max(-60.0, min(60.0, z))
    return math.exp(z)


def abs_activation(z):
    return abs(z)


def hat_activation(z):
    return max(0.0, 1 - abs(z))


def square_activation(z):
    return z ** 2


def cube_activation(z):
    return z ** 3


[docs]class InvalidActivationFunction(TypeError): pass
[docs]def validate_activation(function): if not isinstance(function, (types.BuiltinFunctionType, types.FunctionType, types.LambdaType)): raise InvalidActivationFunction("A function object is required.") if function.__code__.co_argcount != 1: # avoid deprecated use of `inspect` raise InvalidActivationFunction("A single-argument function is required.")
[docs]class ActivationFunctionSet(object): """ Contains the list of current valid activation functions, including methods for adding and getting them. """ def __init__(self): self.functions = {} self.add('sigmoid', sigmoid_activation) self.add('tanh', tanh_activation) self.add('sin', sin_activation) self.add('gauss', gauss_activation) self.add('relu', relu_activation) self.add('elu', elu_activation) self.add('lelu', lelu_activation) self.add('selu', selu_activation) self.add('softplus', softplus_activation) self.add('identity', identity_activation) self.add('clamped', clamped_activation) self.add('inv', inv_activation) self.add('log', log_activation) self.add('exp', exp_activation) self.add('abs', abs_activation) self.add('hat', hat_activation) self.add('square', square_activation) self.add('cube', cube_activation)
[docs] def add(self, name, function): validate_activation(function) self.functions[name] = function
[docs] def get(self, name): f = self.functions.get(name) if f is None: raise InvalidActivationFunction("No such activation function: {0!r}".format(name)) return f
[docs] def is_valid(self, name): return name in self.functions