mknn_distance_eval.h File Reference

MknnDistanceEval is the function used for comparing objects. More...

#include "../metricknn_c.h"

Go to the source code of this file.

Functions
double	mknn_distanceEval_evalTh (MknnDistanceEval *distance_eval, void *object_left, void *object_right, double current_threshold)
	Evaluates the distance between object1 and object2. More...
double	mknn_distanceEval_eval (MknnDistanceEval *distance_eval, void *object_left, void *object_right)
	Evaluates the distance between object1 and object2. More...
MknnDistance *	mknn_distanceEval_getDistance (MknnDistanceEval *distance_eval)
	returns the distance declared for the object. More...
MknnDomain *	mknn_distanceEval_getDomainLeft (MknnDistanceEval *distance_eval)
	returns the domain declared for the object at the left. More...
MknnDomain *	mknn_distanceEval_getDomainRight (MknnDistanceEval *distance_eval)
	returns the domain declared for the object at the right. More...
void	mknn_distanceEval_release (MknnDistanceEval *distance_eval)
	Releases the distance eval. More...

Detailed Description

MknnDistanceEval is the function used for comparing objects.

In order to compare objects, a MknnDistance is used to instantiate one or more MknnDistanceEval objects (one for each parallel thread). The MknnDistanceEval object computes the distance between two objects of a given domain.

The MknnDistanceEval is created by the method mknn_distance_newDistanceEval, which requires the actual domain of the objects to be compared.

A search method uses the MknnDistance to create as many MknnDistanceEval as threads will be used to solve the search. During the search, each thread uses a single MknnDistanceEval.

Function Documentation

double mknn_distanceEval_eval	(	MknnDistanceEval *	distance_eval,
		void *	object_left,
		void *	object_right
	)

Evaluates the distance between object1 and object2.

Remarks

Note about Multi-threading: this method can be called in parallel by several threads as long as each thread owns a different distance_eval object, i.e. a distance_eval object cannot be used at the same time by different threads.

Parameters

distance_eval	distance object.
object_left	left object to be evaluated.
object_right	right object to be evaluated.

Returns

the distance value between object_left and object_right which must be a number >= 0.

double mknn_distanceEval_evalTh	(	MknnDistanceEval *	distance_eval,
		void *	object_left,
		void *	object_right,
		double	current_threshold
	)

Evaluates the distance between object1 and object2.

The parameter current_threshold can be used to save some computation: if during the computation it is known that the value of the distance will surpass current_threshold, the computation is terminated and return some value greater than current_threshold. Note that this can only be fulfilled by distances whose computation produces increasing partial results (as the euclidean distance).

Remarks

Note about Multi-threading: this method can be called in parallel by several threads as long as each thread owns a different distance_eval object, i.e. a distance_eval object cannot be used at the same time by different threads.

Parameters

distance_eval	distance object.
object_left	left object to be evaluated.
object_right	right object to be evaluated.
current_threshold	is the value of the current k-th candidate in a search. This value may be used to trigger an early termination of the distance computation.

Returns

the distance value between object_left and object_right which must be a number >= 0.

MknnDistance* mknn_distanceEval_getDistance

(

MknnDistanceEval *

distance_eval

)

returns the distance declared for the object.

Parameters

distance_eval

Returns

the distance declared for the object.

MknnDomain* mknn_distanceEval_getDomainLeft

(

MknnDistanceEval *

distance_eval

)

returns the domain declared for the object at the left.

Parameters

distance_eval

Returns

the domain declared for the object at the left.

MknnDomain* mknn_distanceEval_getDomainRight

(

MknnDistanceEval *

distance_eval

)

returns the domain declared for the object at the right.

Parameters

distance_eval

Returns

the domain declared for the object at the right.

void mknn_distanceEval_release

(

MknnDistanceEval *

distance_eval

)

Releases the distance eval.

Parameters

distance_eval