uk.ac.starlink.util

Class SplitPolicy

java.lang.Object

uk.ac.starlink.util.SplitPolicy

public class SplitPolicy
extends java.lang.Object

Defines the details of a concurrency policy as used by SplitProcessor.

Since:

5 Nov 2019

Field Summary

Fields

Modifier and Type	Field and Description
static short	DFLT_MAX_TASKS_PER_CORE Default value for maximum average number of subtasks per core.
static int	DFLT_MIN_TASK_SIZE Default value for minimum subtask size.
static SplitPolicy	DFLT_POLICY Default splitting policy.

Constructor Summary

Constructors

Constructor and Description
SplitPolicy() Constructs a policy with default configuration.
SplitPolicy(java.util.function.Supplier<java.util.concurrent.ForkJoinPool> fjPoolSupplier, int minTaskSize, short maxTasksPerCore) Constructs a policy with supplied configuration options.

Method Summary

Modifier and Type	Method and Description
java.util.concurrent.ForkJoinPool	getForkJoinPool() Returns the ForkJoinPool used by this policy.
short	getMaxTasksPerCore() Returns the maximum number of tasks (on average) to be executed on each core as a result of decomposition, or zero for no limit.
int	getMinTaskSize() Returns the smallest task size used by this policy.
java.lang.String	toString()
boolean	willAttemptSplit(Splittable<?> content) Indicates whether an attempt should be made to split a splittable in order to process it.

Methods inherited from class java.lang.Object

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

Field Detail

DFLT_MIN_TASK_SIZE

public static final int DFLT_MIN_TASK_SIZE

Default value for minimum subtask size. The current value for this is conservative, in that it will not result in concurrency for relatively small jobs. The (JDK8) ForkJoinTask javadocs recommend as a rough rule of thumb a value in the range of 1e2-1e4 steps, so this possibly could be reduced.

See Also:

Constant Field Values

DFLT_MAX_TASKS_PER_CORE

public static final short DFLT_MAX_TASKS_PER_CORE

Default value for maximum average number of subtasks per core. The value of 8 is suggested by the example parallel computation framework sketch in the (JDK8) Spliterator javadocs.

See Also:

Constant Field Values

DFLT_POLICY

public static final SplitPolicy DFLT_POLICY

Default splitting policy.

Constructor Detail

SplitPolicy

public SplitPolicy()

Constructs a policy with default configuration.

SplitPolicy

public SplitPolicy(java.util.function.Supplier<java.util.concurrent.ForkJoinPool> fjPoolSupplier,
                   int minTaskSize,
                   short maxTasksPerCore)

Constructs a policy with supplied configuration options.

Parameters:

fjPoolSupplier - supplier for fork/join pool for execution, or null to use the common pool; if non-null this supplier will be used a maximum of once for lazy acquisition

minTaskSize - smallest acceptable size of sub-task to split tasks into, or non-positive value for default (DFLT_MIN_TASK_SIZE)

maxTasksPerCore - maximum number of tasks (on average) to be executed on each core as a result of decomposition, or zero for no limit, or negative value for default limit (DFLT_MAX_TASKS_PER_CORE)

Method Detail

getForkJoinPool

public java.util.concurrent.ForkJoinPool getForkJoinPool()

Returns the ForkJoinPool used by this policy.

Returns:

forkjoinpool

getMinTaskSize

public int getMinTaskSize()

Returns the smallest task size used by this policy.

Returns:

smallest acceptable size of sub-task to split tasks into

getMaxTasksPerCore

public short getMaxTasksPerCore()

Returns the maximum number of tasks (on average) to be executed on each core as a result of decomposition, or zero for no limit.

Returns:

maximum tasks per core, or zero

willAttemptSplit

public boolean willAttemptSplit(Splittable<?> content)

Indicates whether an attempt should be made to split a splittable in order to process it. If it's too small for instance, false will be returned.

Parameters:

content - splittable

Returns:

true iff processing will try to split content

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object