uk.ac.starlink.util

Class SplitProcessor<S extends Splittable<S>>

java.lang.Object

uk.ac.starlink.util.SplitProcessor<S>

public abstract class SplitProcessor<S extends Splittable<S>>
extends Object

Invokes processing on Splittables.

Instances of this class perform a similar function to that implemented in the Stream class from the Java 8 Streams framework. There is much less functionality and cleverness here, but the behaviour is predictable and permits external iteration rather than imposing internal iteration.

Since:

9 Sep 2019

Author:

Mark Taylor

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	SplitProcessor(String name) Constructor.

Method Summary

Modifier and Type	Method and Description
abstract <A> A	collect(SplitCollector<S,A> collector, S content) Collects content from a splittable object into an accumulator, as defined by a provided collector.
static <S extends Splittable<S>> SplitProcessor<S>	createBasicParallelProcessor(SplitPolicy policy) Returns a SplitProcessor instance that works in parallel, with one accumulator created for every forked subtask.
static <S extends Splittable<S>> SplitProcessor<S>	createPoolParallelProcessor(SplitPolicy policy) Returns a SplitProcessor instance that works in parallel, with a pool of reusable accumulators shared by forked subtasks.
static <S extends Splittable<S>> SplitProcessor<S>	createSequentialProcessor() Returns a SplitProcessor instance that performs sequential processing.
static <S extends Splittable<S>> SplitProcessor<S>	createStandardProcessor(SplitPolicy policy, boolean isPool) Returns a suitable processor instance.
String	toString()
abstract boolean	willAttemptSplit(S content) Indicates whether this processor will attempt to split the given splittable object when processing it.

Methods inherited from class java.lang.Object

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

Constructor Detail

SplitProcessor

protected SplitProcessor(String name)

Constructor.

Parameters:

name - name of this instance

Method Detail

willAttemptSplit

public abstract boolean willAttemptSplit(S content)

Indicates whether this processor will attempt to split the given splittable object when processing it. If for instance its size is known to be too small for this processor's policy, false will be returned.

Parameters:

content - splittable object

Returns:

true iff splitting will be attempted during processing

collect

public abstract <A> A collect(SplitCollector<S,A> collector,
                              S content)

Collects content from a splittable object into an accumulator, as defined by a provided collector.

Parameters:

collector - defines collection semantics

content - input data

Returns:

accumulator into which content has been collected

toString

public String toString()

Overrides:

toString in class Object

createSequentialProcessor

public static <S extends Splittable<S>> SplitProcessor<S> createSequentialProcessor()

Returns a SplitProcessor instance that performs sequential processing.

Returns:

new processor

createBasicParallelProcessor

public static <S extends Splittable<S>> SplitProcessor<S> createBasicParallelProcessor(SplitPolicy policy)

Returns a SplitProcessor instance that works in parallel, with one accumulator created for every forked subtask.

Parameters:

policy - parallel execution policy, or null for default

Returns:

new processor

createPoolParallelProcessor

public static <S extends Splittable<S>> SplitProcessor<S> createPoolParallelProcessor(SplitPolicy policy)

Returns a SplitProcessor instance that works in parallel, with a pool of reusable accumulators shared by forked subtasks. This is expected to be beneficial if accumulator construction or combination is computationally expensive. However, it's probably not necessary when working with accumulators that simply have a large memory footprint, since multiple accumulators ought not to be in simultaneous use either way.

Parameters:

policy - parallel execution policy, or null for default

Returns:

new processor

createStandardProcessor

public static <S extends Splittable<S>> SplitProcessor<S> createStandardProcessor(SplitPolicy policy,
                                                                                  boolean isPool)

Returns a suitable processor instance. This will defer to one of createSequentialProcessor, createBasicParallelProcessor or createPoolParallelProcessor, depending on its arguments.

Parameters:

policy - parallel execution policy, or null for default

isPool - true to prefer pooling

Returns:

new processor