pt.runtime
Interface Reduction<E>

Type Parameters:

E - The type of elements to be reduced

public interface Reduction<E>

Define a reduction of two items into one. This definition may then be used to reduce a collection of items into one item. This is primarily intended for reducing the results from a multi-task (see TaskIDGroup.reduce(Reduction)).

This approach allows the programmer to easily define complex reductions that could even involve entire data structures, for example concatenating lists or maps. A reduction must be:

• associative (the order of performing the reduction makes no difference), and
• commutative (the order of the items to be reduced makes no difference) since the interface does not specify order.

For convenience, some pre-defined reductions are included to be used for common types.

Author:

Nasser Giacaman, Oliver Sinnen

Field Summary

static Reduction<java.lang.Object[]>	ArrayCOMBINE Combines the elements from the arrays into a new array.
static Reduction<java.lang.Boolean>	BooleanAND Performs a Boolean AND
static Reduction<java.lang.Boolean>	BooleanOR Performs a Boolean OR
static Reduction<java.lang.Double>	DoubleMAX Perform a maximum reduction for Double values.
static Reduction<java.lang.Double>	DoubleMIN Perform a minimum reduction for Double values.
static Reduction<java.lang.Double>	DoubleSUM Perform a sum reduction for Double values.
static Reduction<java.lang.Integer>	IntegerMAX Perform a maximum reduction for Integer values.
static Reduction<java.lang.Integer>	IntegerMIN Perform a minimum reduction for Integer values.
static Reduction<java.lang.Integer>	IntegerSUM Perform a sum reduction for Integer values.

Method Summary

E	combine(E a, E b) Specifies a reduction as defined by 2 elements into 1.

Field Detail

IntegerMIN

static final Reduction<java.lang.Integer> IntegerMIN

Perform a minimum reduction for Integer values.

IntegerMAX

static final Reduction<java.lang.Integer> IntegerMAX

Perform a maximum reduction for Integer values.

IntegerSUM

static final Reduction<java.lang.Integer> IntegerSUM

Perform a sum reduction for Integer values.

DoubleMIN

static final Reduction<java.lang.Double> DoubleMIN

Perform a minimum reduction for Double values.

DoubleMAX

static final Reduction<java.lang.Double> DoubleMAX

Perform a maximum reduction for Double values.

DoubleSUM

static final Reduction<java.lang.Double> DoubleSUM

Perform a sum reduction for Double values.

ArrayCOMBINE

static final Reduction<java.lang.Object[]> ArrayCOMBINE

Combines the elements from the arrays into a new array.

BooleanOR

static final Reduction<java.lang.Boolean> BooleanOR

Performs a Boolean OR

BooleanAND

static final Reduction<java.lang.Boolean> BooleanAND

Performs a Boolean AND

Method Detail

combine

E combine(E a,
          E b)

Specifies a reduction as defined by 2 elements into 1. The reduction must obey the following constraints:

• associative: the order of evaluating the reduction makes no difference, and
• commutative the order of the values (i.e. a and b) makes no difference.

  Parameters:

  a - The first element in the reduction

  b - The second element in the reduction

  Returns:

  The result of reducing a with b.