jsat.distributions.kernels

Class BaseKernelTrick

java.lang.Object

jsat.distributions.kernels.BaseKernelTrick

All Implemented Interfaces:

Serializable, Cloneable, KernelTrick, Parameterized

Direct Known Subclasses:

LinearKernel, PolynomialKernel, SigmoidKernel

public abstract class BaseKernelTrick
extends Object
implements KernelTrick

This provides a simple base implementation for the cache related methods in Kernel Trick. By default they will all call KernelTrick.eval(jsat.linear.Vec, jsat.linear.Vec) directly. For this reason supportsAcceleration() defaults to returning false. If the Kernel supports cache acceleration, evalSum(java.util.List, java.util.List, double[], jsat.linear.Vec, int, int) will make use of the acceleration. All other methods must be overloaded.

Author:

Edward Raff

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
BaseKernelTrick()

Method Summary

Modifier and Type	Method and Description
void	addToCache(Vec newVec, List<Double> cache) Appends the new cache values for the given vector to the list of cache values.
abstract KernelTrick	clone()
double	eval(int a, int b, List<? extends Vec> trainingSet, List<Double> cache) Produces the correct kernel evaluation given the training set and the cache generated by KernelTrick.getAccelerationCache(List).
double	eval(int a, Vec b, List<Double> qi, List<? extends Vec> vecs, List<Double> cache) Computes the kernel product between one vector in the original list of vectors with that of another vector not from the original list, but had information generated by KernelTrick.getQueryInfo(jsat.linear.Vec).
double	evalSum(List<? extends Vec> finalSet, List<Double> cache, double[] alpha, Vec y, int start, int end) Performs an efficient summation of kernel products of the form ∑ αi k(xi, y) where x are the final set of vectors, and α the associated scalar multipliers
double	evalSum(List<? extends Vec> finalSet, List<Double> cache, double[] alpha, Vec y, List<Double> qi, int start, int end) Performs an efficient summation of kernel products of the form ∑ αi k(xi, y) where x are the final set of vectors, and α the associated scalar multipliers
List<Double>	getAccelerationCache(List<? extends Vec> trainingSet) Creates a new list cache values from a given list of training set vectors.
List<Double>	getQueryInfo(Vec q) Pre computes query information that would have be generated if the query was a member of the original list of vectors when calling KernelTrick.getAccelerationCache(java.util.List) .
boolean	normalized() This method indicates if a kernel is a normalized kernel or not.
boolean	supportsAcceleration() Indicates if this kernel supports building an acceleration cache using the KernelTrick.getAccelerationCache(List) and associated cache accelerated methods.

Methods inherited from class java.lang.Object

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

Methods inherited from interface jsat.distributions.kernels.KernelTrick

eval, toString

Methods inherited from interface jsat.parameters.Parameterized

getParameter, getParameters

Constructor Detail

BaseKernelTrick

public BaseKernelTrick()

Method Detail

supportsAcceleration

public boolean supportsAcceleration()

Description copied from interface: KernelTrick

Indicates if this kernel supports building an acceleration cache using the KernelTrick.getAccelerationCache(List) and associated cache accelerated methods. By default this method will return false. If true, then a cache can be obtained from this matrix and used in conjunction with KernelTrick.eval(int, Vec, List, List, List) and KernelTrick.eval(int, int, List, List) to perform kernel products.

Specified by:

supportsAcceleration in interface KernelTrick

Returns:

true if cache acceleration is supported for this kernel, false otherwise.

getAccelerationCache

public List<Double> getAccelerationCache(List<? extends Vec> trainingSet)

Description copied from interface: KernelTrick

Creates a new list cache values from a given list of training set vectors. If this kernel does not support acceleration, null will be returned.

Specified by:

getAccelerationCache in interface KernelTrick

Parameters:

trainingSet - the list of training set vectors

Returns:

a list of cache values that may be used by this kernel

getQueryInfo

public List<Double> getQueryInfo(Vec q)

Description copied from interface: KernelTrick

Pre computes query information that would have be generated if the query was a member of the original list of vectors when calling KernelTrick.getAccelerationCache(java.util.List) . This can then be used if a large number of kernel computations are going to be done against points in the original set for a point that is outside the original space.

If this kernel does not support acceleration, null will be returned.

Specified by:

getQueryInfo in interface KernelTrick

Parameters:

q - the query point to generate cache information for

Returns:

the cache information for the query point

addToCache

public void addToCache(Vec newVec,
                       List<Double> cache)

Description copied from interface: KernelTrick

Appends the new cache values for the given vector to the list of cache values. This method is present for online style kernel learning algorithms, where the set of vectors is not known in advance. When a vector is added to the set of kernel vectors, its cache values can be added using this method.

The results of calling this sequentially on a lit of vectors starting with an empty double list is equivalent to getting the results from calling KernelTrick.getAccelerationCache(java.util.List)

If this kernel does not support acceleration, this method call will function as a nop.

Specified by:

addToCache in interface KernelTrick

Parameters:

newVec - the new vector to add to the cache values

cache - the original list of cache values to add to

eval

public double eval(int a,
                   int b,
                   List<? extends Vec> trainingSet,
                   List<Double> cache)

Description copied from interface: KernelTrick

Produces the correct kernel evaluation given the training set and the cache generated by KernelTrick.getAccelerationCache(List). The training vectors should be in the same order.

Specified by:

eval in interface KernelTrick

Parameters:

a - the index of the first training vector

b - the index of the second training vector

trainingSet - the list of training set vectors

cache - the double list of cache values generated by this kernel for the given training set

Returns:

the same kernel evaluation result as KernelTrick.eval(jsat.linear.Vec, jsat.linear.Vec)

eval

public double eval(int a,
                   Vec b,
                   List<Double> qi,
                   List<? extends Vec> vecs,
                   List<Double> cache)

Description copied from interface: KernelTrick

Computes the kernel product between one vector in the original list of vectors with that of another vector not from the original list, but had information generated by KernelTrick.getQueryInfo(jsat.linear.Vec).
If the cache input is null, then KernelTrick.eval(jsat.linear.Vec, jsat.linear.Vec) will be called directly.

Specified by:

eval in interface KernelTrick

Parameters:

a - the index of the vector in the cache

b - the other vector

qi - the query information about b

vecs - the list of vectors used to build the cache

cache - the cache associated with the given list of vectors

Returns:

the kernel product of the two vectors

evalSum

public double evalSum(List<? extends Vec> finalSet,
                      List<Double> cache,
                      double[] alpha,
                      Vec y,
                      int start,
                      int end)

Description copied from interface: KernelTrick

Performs an efficient summation of kernel products of the form
∑ α_i k(x_i, y)
where x are the final set of vectors, and α the associated scalar multipliers

Specified by:

evalSum in interface KernelTrick

Parameters:

finalSet - the final set of vectors

cache - the cache associated with the final set of vectors

alpha - the coefficients associated with each vector

y - the vector to perform the summed kernel products against

start - the starting index (inclusive) to sum from

end - the ending index (exclusive) to sum from

Returns:

the sum of the multiplied kernel products

evalSum

public double evalSum(List<? extends Vec> finalSet,
                      List<Double> cache,
                      double[] alpha,
                      Vec y,
                      List<Double> qi,
                      int start,
                      int end)

Description copied from interface: KernelTrick

Performs an efficient summation of kernel products of the form
∑ α_i k(x_i, y)
where x are the final set of vectors, and α the associated scalar multipliers

Specified by:

evalSum in interface KernelTrick

Parameters:

finalSet - the final set of vectors

cache - the cache associated with the final set of vectors

alpha - the coefficients associated with each vector

y - the vector to perform the summed kernel products against

qi - the query information about y

start - the starting index (inclusive) to sum from

end - the ending index (exclusive) to sum from

Returns:

the sum of the multiplied kernel products

clone

public abstract KernelTrick clone()

Specified by:

clone in interface KernelTrick

Overrides:

clone in class Object

normalized

public boolean normalized()

Description copied from interface: KernelTrick

This method indicates if a kernel is a normalized kernel or not. A normalized kernel is one in which k(x,x) = 1 for the same object, and no value greater than 1 can be returned.

Specified by:

normalized in interface KernelTrick

Returns:

true if this is a normalized kernel. false otherwise.