com.saxonica.ee.optim

Class MultithreadedItemMappingIterator<F extends Item<?>,T extends Item<?>>

java.lang.Object

net.sf.saxon.expr.ItemMappingIterator<F,T>

com.saxonica.ee.optim.MultithreadedItemMappingIterator<F,T>

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, LastPositionFinder, SequenceIterator<T>, LookaheadIterator<T>

public class MultithreadedItemMappingIterator<F extends Item<?>,T extends Item<?>>
extends ItemMappingIterator<F,T>

Parallel-processing version of the ItemMappingIterator class, which executes a mapping function for each item in a sequence. In this implementation (which is designed initially for use by the collection() function), the order of items in the result sequence retains the order of items in the input sequence.

Field Summary

Fields inherited from interface net.sf.saxon.om.SequenceIterator

ATOMIZING, GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Constructor Summary

Constructors

Constructor and Description
MultithreadedItemMappingIterator(SequenceIterator<F> base, ItemMappingFunction<F,T> action)

Method Summary

Modifier and Type	Method and Description
void	close() The user of a SequenceIterator is encouraged to call the close() method if no further items are required from the sequence of items delivered by the SequenceIterator.
protected int	getMaxThreads() Overridable method that decides how many threads to use.
protected java.util.concurrent.ExecutorService	makeExecutorService(int maxThreads) Overridable method to create an ExecutorService with a given concurrency
T	next() Get the next item in the sequence.

Methods inherited from class net.sf.saxon.expr.ItemMappingIterator

getBaseIterator, getLength, getMappingFunction, getProperties, hasNext, isOneToOne, setOneToOne

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.saxon.om.SequenceIterator

forEachOrFail, materialize

Constructor Detail

MultithreadedItemMappingIterator

public MultithreadedItemMappingIterator(SequenceIterator<F> base,
                                        ItemMappingFunction<F,T> action)
                                 throws XPathException

Throws:

XPathException

Method Detail

getMaxThreads

protected int getMaxThreads()

Overridable method that decides how many threads to use. The default implementation returns the value of Runtime.getRuntime().availableProcessors(), or 1 if greater.

Returns:

the maximum number of threads to use.

makeExecutorService

protected java.util.concurrent.ExecutorService makeExecutorService(int maxThreads)

Overridable method to create an ExecutorService with a given concurrency

Parameters:

maxThreads - the maximum number of threads to be used

Returns:

a suitable ExecutorService

next

public T next()
       throws XPathException

Description copied from interface: SequenceIterator

Get the next item in the sequence. This method changes the state of the iterator.

Specified by:

next in interface SequenceIterator<T extends Item<?>>

Overrides:

next in class ItemMappingIterator<F extends Item<?>,T extends Item<?>>

Returns:

the next item, or null if there are no more items. Once a call on next() has returned null, no further calls should be made. The preferred action for an iterator if subsequent calls on next() are made is to return null again, and all implementations within Saxon follow this rule.

Throws:

XPathException - if an error occurs retrieving the next item

close

public void close()

The user of a SequenceIterator is encouraged to call the close() method if no further items are required from the sequence of items delivered by the SequenceIterator. This allows resources to be released. A SequenceIterator is NOT normally closed explicitly if it has been read to completion. This implementation of the close() method shuts down the ExecutorService used to schedule threads.

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface SequenceIterator<T extends Item<?>>

Overrides:

close in class ItemMappingIterator<F extends Item<?>,T extends Item<?>>