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gnn_logistic : Logistic Sigmoid Activation Function.
[Atomic Nodes.]

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Detailed Description

The gnn_logistic datatype implements a node that computes the function:

where .

This function is a member of the more general class of sigmoid functions, which have the property to "squash" its inputs to a very restricted output interval.

The Logistic Sigmoid is assymmetric and its outputs lie between . It has been said that it leads to slower convergence in training than the Hyperbolic Tangent.

Functions
int	gnn_logistic_f (gnn_node *node, const gsl_vector *x, const gsl_vector *w, gsl_vector *y)
	Computes the output.
int	gnn_logistic_dx (gnn_node *node, const gsl_vector *x, const gsl_vector *w, const gsl_vector *dy, gsl_vector *dx)
	Computes .
gnn_node *	gnn_logistic_new (int input_size, double a, double b)
	Creates a Logistic Sigmoid activation function node.
gnn_node *	gnn_logistic_standard_new (int input_size)
	Creates a standard Logistic Sigmoid function node.
double	gnn_logistic_get_a (gnn_node *node)
	Returns the amplitude constant .
void	gnn_logistic_set_a (gnn_node *node, double a)
	Sets the amplitude constant .
double	gnn_logistic_get_b (gnn_node *node)
	Gets the streching factor .
void	gnn_logistic_set_b (gnn_node *node, double b)
	Sets the streching factor .

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Function Documentation

int gnn_logistic_dx (  gnn_node *    node, const gsl_vector *    x, const gsl_vector *    w, const gsl_vector *    dy, gsl_vector *    dx )  [static]

This functions computes the gradient of the logistic sigmoid function, given dedy ( ). The function is, Parameters: node  A pointer to a gnn_logistic node. x  The input vector . w  The parameter vector (which is empty in this case). dy  The vector . dx  The output buffer vector . Returns: Returns 0 on success. Definition at line 154 of file gnn_logistic.c.

int gnn_logistic_f (  gnn_node *    node, const gsl_vector *    x, const gsl_vector *    w, gsl_vector *    y )  [static]

This functions evaluates the logistic sigmoid function. Parameters: node  A pointer to a gnn_logistic node. x  The input vector . w  The parameter vector (which is empty in this case). y  The output buffer vector . Returns: Returns 0 on success. Definition at line 107 of file gnn_logistic.c.

double gnn_logistic_get_a (  gnn_node *    node )

Parameters: node  A pointer to a gnn_logistic node. Returns: The amplitude of the sigmoid. Definition at line 282 of file gnn_logistic.c.

double gnn_logistic_get_b (  gnn_node *    node )

Parameters: node  A pointer to a gnn_logistic node. Returns: The streching factor . Definition at line 308 of file gnn_logistic.c.

gnn_node* gnn_logistic_new (  int    input_size, double    a, double    b )

This function creates a node of the gnn_logistic type. This node computes where , and constants. Parameters: input_size  The input size . a  The factor. b  The factor. Returns: A pointer to a new gnn_logistic node. Definition at line 211 of file gnn_logistic.c.

void gnn_logistic_set_a (  gnn_node *    node, double    a )

Parameters: node  A pointer to a gnn_logistic node. a  The amplitude factor. Definition at line 295 of file gnn_logistic.c.

void gnn_logistic_set_b (  gnn_node *    node, double    b )

Parameters: node  A pointer to a gnn_logistic node. b  The new streching factor . Definition at line 321 of file gnn_logistic.c.

gnn_node* gnn_logistic_standard_new (  int    input_size )

This function creates a node of the gnn_logistic type: where . Parameters: input_size  The input size . Returns: A pointer to a new gnn_logistic node. Definition at line 269 of file gnn_logistic.c.

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