it.uniroma2.sag.kelp.kernel

Class Kernel

java.lang.Object

it.uniroma2.sag.kelp.kernel.Kernel

Direct Known Subclasses:

DirectKernel, KernelCombination, KernelComposition

public abstract class Kernel
extends Object

Abstract class for a generic kernel function

Author:

Simone Filice

Constructor Summary

Constructors

Constructor and Description
Kernel()

Method Summary

Methods

Modifier and Type	Method and Description
void	disableCache() Disables the kernel cache
KernelCache	getKernelCache() Returns the cache in which storing the kernel operations in the RKHS defined by this kernel
long	getKernelComputations() Returns the number of times the kernel function has been invoked
long	getNumberOfHits() Returns the number of times a cache hit happened
long	getNumberOfMisses() Returns the number of times a cache miss happened
SquaredNormCache	getSquaredNormCache() Returns the cache in which storing the squared norms in the RKHS defined by this kernel
float	innerProduct(Example exA, Example exB) Returns the kernel similarity between the given examples.
protected abstract float	kernelComputation(Example exA, Example exB) Returns the kernel similarity between the given examples.
static Kernel	load(String inputFilePath) Load a kernel function from a file path.
void	reset() Resets the kernel statistics (number of kernel computations, cache hits and misses)
static void	save(Kernel kernel, String outputFilePath) Save the input kernel in a file.
void	setKernelCache(KernelCache cache) Sets the cache in which storing the kernel operations in the RKHS defined by this kernel
void	setSquaredNormCache(SquaredNormCache normCache) Sets the cache in which storing the squared norms in the RKHS defined by this kernel
float	squaredNorm(Example example) Returns the squared norm of the given example in the RKHS defined by this kernel
float	squaredNormOfTheDifference(Example exA, Example exB) Returns the squared norm of the difference between the given examples in the RKHS.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Kernel

public Kernel()

Method Detail

innerProduct

public final float innerProduct(Example exA,
                 Example exB)

Returns the kernel similarity between the given examples. This corresponds to the inner product in the implicit Reproducing Kernel Hilbert Space (RKHS)

Parameters:

exA - the first example

exB - the second example

Returns:

the kernel operation between exA and exB

setSquaredNormCache

public void setSquaredNormCache(SquaredNormCache normCache)

Sets the cache in which storing the squared norms in the RKHS defined by this kernel

Parameters:

normCache - the cache for the squared norms

getSquaredNormCache

public SquaredNormCache getSquaredNormCache()

Returns the cache in which storing the squared norms in the RKHS defined by this kernel

Returns:

the cache for the squared norms

setKernelCache

public void setKernelCache(KernelCache cache)

Sets the cache in which storing the kernel operations in the RKHS defined by this kernel

Parameters:

cache - the cache for the kernel operations

getKernelCache

public KernelCache getKernelCache()

Returns the cache in which storing the kernel operations in the RKHS defined by this kernel

Parameters:

cache - the cache for the kernel operations

kernelComputation

protected abstract float kernelComputation(Example exA,
                      Example exB)

Returns the kernel similarity between the given examples. This corresponds to the inner product in the implicit Reproducing Kernel Hilbert Space (RKHS)

Parameters:

exA - the first example

exB - the second example

Returns:

the kernel operation between exA and exB

squaredNorm

public float squaredNorm(Example example)

Returns the squared norm of the given example in the RKHS defined by this kernel

Parameters:

example - the example whose squared norm must be computed

Returns:

the squared norm in the RKHS

squaredNormOfTheDifference

public float squaredNormOfTheDifference(Example exA,
                               Example exB)

Returns the squared norm of the difference between the given examples in the RKHS. It computes ||exA-exB||^2 = + - 2* where defines the inner product between two generic examples a and b in the RKHS defined by this kernel

Parameters:

exA - the first example

exB - the second example

Returns:

the squared norm of the difference in the RKHS

disableCache

public void disableCache()

Disables the kernel cache

getKernelComputations

public long getKernelComputations()

Returns the number of times the kernel function has been invoked

Returns:

the number of performed kernel operations

getNumberOfHits

public long getNumberOfHits()

Returns the number of times a cache hit happened

Returns:

the number of cache hits

getNumberOfMisses

public long getNumberOfMisses()

Returns the number of times a cache miss happened

Returns:

the number of cache misses

reset

public void reset()

Resets the kernel statistics (number of kernel computations, cache hits and misses)

save

public static void save(Kernel kernel,
        String outputFilePath)
                 throws FileNotFoundException,
                        IOException

Save the input kernel in a file. If the .gz extension is specified, the file is compressed.

Parameters:

kernel - The input kernel

outputFilePath - The output file path

Throws:

FileNotFoundException

IOException

load

public static Kernel load(String inputFilePath)
                   throws FileNotFoundException,
                          IOException

Load a kernel function from a file path. If the .gz extension is specified, the file considered compressed.

Parameters:

kernel - The input kernel

outputFilePath - The output file path

Throws:

FileNotFoundException

IOException