com.bigdata.rdf.graph.impl.frontier

Class StaticFrontier2

java.lang.Object

com.bigdata.rdf.graph.impl.frontier.StaticFrontier2

All Implemented Interfaces:

IStaticFrontier, Iterable<org.openrdf.model.Value>

public class StaticFrontier2
extends Object
implements IStaticFrontier

An implementation of a "static" frontier that grows and reuses the backing vertex array.

Note: This implementation has package private methods that permit certain kinds of mutation.

Author:

Bryan Thompson

Constructor Summary

Constructors

Constructor and Description
StaticFrontier2()

Method Summary

Methods

Modifier and Type	Method and Description
void	copyIntoResetFrontier(int off, IArraySlice<org.openrdf.model.Value> slice) Copy a slice into the backing array.
boolean	isCompact() Return true iff the frontier is known to be compact (no duplicate vertices).
boolean	isEmpty() Return true if the frontier is known to be empty.
Iterator<org.openrdf.model.Value>	iterator()
void	resetAndEnsureCapacity(int minCapacity) Grow the backing array iff necessary.
void	resetFrontier(int minCapacity, boolean sort, Iterator<org.openrdf.model.Value> itr) Reset the frontier from the supplied vertices.
void	setCompact(boolean newValue)
int	size() The number of vertices in the frontier.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

StaticFrontier2

public StaticFrontier2()

Method Detail

isCompact

public boolean isCompact()

Description copied from interface: IStaticFrontier

Return true iff the frontier is known to be compact (no duplicate vertices).

Note: If the frontier is not compact, then the IGASEngine may optionally elect to eliminate duplicate work when it schedules the vertices in the frontier.

Note: A non-compact frontier can arise when the IGASScheduler chooses a per-thread approach and then copies the per-thread segments onto the shared backing array in parallel. This can reduce the time between rounds, which can speed up the overall execution of the algorithm significantly.

Specified by:

isCompact in interface IStaticFrontier

setCompact

public void setCompact(boolean newValue)

size

public int size()

Description copied from interface: IStaticFrontier

The number of vertices in the frontier. TODO Long? Or just do not allow in scale-out?

Specified by:

size in interface IStaticFrontier

isEmpty

public boolean isEmpty()

Description copied from interface: IStaticFrontier

Return true if the frontier is known to be empty.

Specified by:

isEmpty in interface IStaticFrontier

iterator

public Iterator<org.openrdf.model.Value> iterator()

Specified by:

iterator in interface Iterable<org.openrdf.model.Value>

resetAndEnsureCapacity

public void resetAndEnsureCapacity(int minCapacity)

Grow the backing array iff necessary. Regardless, the entries from end of the current view to the first non-null are cleared. This is done to faciltiate GC by clearing references that would otherwise remain if/when the frontier contracted.

Parameters:

minCapacity - The required minimum capacity.

copyIntoResetFrontier

public void copyIntoResetFrontier(int off,
                         IArraySlice<org.openrdf.model.Value> slice)

Copy a slice into the backing array. This method is intended for use by parallel threads. The backing array MUST have sufficient capacity. The threads MUST write to offsets that are known to not overlap. NO checking is done to ensure that the concurrent copy of these slices will not overlap.

Parameters:

off - The offset at which to copy the slice.

slice - The slice.

resetFrontier

public void resetFrontier(int minCapacity,
                 boolean sort,
                 Iterator<org.openrdf.model.Value> itr)

Description copied from interface: IStaticFrontier

Reset the frontier from the supplied vertices.

Specified by:

resetFrontier in interface IStaticFrontier

Parameters:

minCapacity - The minimum capacity of the new frontier. (A minimum capacity is specified since many techniques to compact the frontier can only estimate the required capacity.)

itr - The vertices in the new frontier.

toString

public String toString()

Overrides:

toString in class Object