org.apache.mahout.math.function

Class PlusMult

java.lang.Object

org.apache.mahout.math.function.DoubleDoubleFunction

org.apache.mahout.math.function.PlusMult

public final class PlusMult
extends DoubleDoubleFunction

Only for performance tuning of compute intensive linear algebraic computations. Constructs functions that return one of

• a + b*constant
• a - b*constant
• a + b/constant
• a - b/constant

a and b are variables, constant is fixed, but for performance reasons publicly accessible. Intended to be passed to matrix.assign(otherMatrix,function) methods.

Constructor Summary

Constructors

Constructor and Description
PlusMult(double multiplicator)

Method Summary

Methods

Modifier and Type	Method and Description
double	apply(double a, double b) Returns the result of the function evaluation.
double	getMultiplicator()
boolean	isAssociative() f(x, f(y, z)) = x + c * (y + c * z) = x + c * y + c^2 * z f(f(x, y), z) = (x + c * y) + c * z = x + c * y + c * z true only for c = 0 or c = 1
boolean	isCommutative() x + y * c = y + x * c iff c = 1
boolean	isLikeLeftMult() 0 + y * c = y * c != 0
boolean	isLikeRightMult() x + 0 * c = x != 0
boolean	isLikeRightPlus() x + 0 * c = x
static PlusMult	minusMult(double constant) a - b*constant.
static PlusMult	plusMult(double constant) a + b*constant.
void	setMultiplicator(double multiplicator)

Methods inherited from class org.apache.mahout.math.function.DoubleDoubleFunction

isAssociativeAndCommutative, isDensifying, isLikeMult

Methods inherited from class java.lang.Object

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

Constructor Detail

PlusMult

public PlusMult(double multiplicator)

Method Detail

apply

public double apply(double a,
           double b)

Returns the result of the function evaluation.

Specified by:

apply in class DoubleDoubleFunction

Parameters:

a - a double for the first argument

b - a double for the second argument

Returns:

the result of applying the function

minusMult

public static PlusMult minusMult(double constant)

a - b*constant.

plusMult

public static PlusMult plusMult(double constant)

a + b*constant.

getMultiplicator

public double getMultiplicator()

isLikeRightPlus

public boolean isLikeRightPlus()

x + 0 * c = x

Overrides:

isLikeRightPlus in class DoubleDoubleFunction

Returns:

true iff f(x, 0) = x for any x

isLikeLeftMult

public boolean isLikeLeftMult()

0 + y * c = y * c != 0

Overrides:

isLikeLeftMult in class DoubleDoubleFunction

Returns:

true iff f(0, y) = 0 for any y

isLikeRightMult

public boolean isLikeRightMult()

x + 0 * c = x != 0

Overrides:

isLikeRightMult in class DoubleDoubleFunction

Returns:

true iff f(x, 0) = 0 for any x

isCommutative

public boolean isCommutative()

x + y * c = y + x * c iff c = 1

Overrides:

isCommutative in class DoubleDoubleFunction

Returns:

true iff f(x, y) = f(y, x) for any x, y

isAssociative

public boolean isAssociative()

f(x, f(y, z)) = x + c * (y + c * z) = x + c * y + c^2 * z f(f(x, y), z) = (x + c * y) + c * z = x + c * y + c * z true only for c = 0 or c = 1

Overrides:

isAssociative in class DoubleDoubleFunction

Returns:

true iff f(x, f(y, z)) = f(f(x, y), z) for any x, y, z

setMultiplicator

public void setMultiplicator(double multiplicator)