org.pentaho.aggdes.algorithm.impl

Class AlgorithmImpl

java.lang.Object

org.pentaho.aggdes.algorithm.impl.AlgorithmImpl

All Implemented Interfaces:

Algorithm, Component

Direct Known Subclasses:

AdaptiveMonteCarloAlgorithm, ExhaustiveLatticeAlgorithm, MonteCarloAlgorithm

public abstract class AlgorithmImpl
extends Object
implements Algorithm

Implementation of the Algorithm that uses an exhaustive algorithm. The algorithm constructs the full lattice in memory, and uses a greedy algorithm which, at each step, chooses the aggregate which offers the greatest benefit over the current set of aggregates.

Cost

If there are N levels, then the lattice has size 2N. Let's suppose that the algorithm creates M aggregates before each aggregate sees only a marginal benefit. Then the running time is M * 2N.

The cost and memory usage of the algorithm is prohibitive for all but very small schemas. For example, for a schema with 20 levels and 40 aggregate tables, this requires memory for a lattice of 1 million potential aggregates, and 40 million steps to evaluate choose the actual set of aggregate tables.

Nested Class Summary

Nested classes/interfaces inherited from interface org.pentaho.aggdes.algorithm.Algorithm

Algorithm.CostBenefit, Algorithm.ParameterEnum

Field Summary

Fields

Modifier and Type	Field and Description
protected List<Parameter>	parameterList
protected Schema	schema

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AlgorithmImpl() Creates an AggregateTableAdvisorImpl

Method Summary

Methods

Modifier and Type	Method and Description
void	cancel() Cancels a run.
protected boolean	checkCancelTimeout() Checks whether this algorithm has been canceled or has exceeded its maximum running time.
Aggregate	createAggregate(Schema schema, List<Attribute> attributeList) Creates an Aggregate.
static String	getBaseName(Class<? extends Component> aClass)
String	getName() Returns a name for this component.
List<Parameter>	getParameters() Declares the parameters that this component accepts.
protected void	onStart(Map<Parameter,Object> parameterValues, Progress progress) Called by the Algorithm.run(org.pentaho.aggdes.model.Schema, java.util.Map<org.pentaho.aggdes.model.Parameter, java.lang.Object>, org.pentaho.aggdes.algorithm.Progress) method, resets the 'canceled' flag and sets the start time for timeout purposes.
protected ResultImpl	runAlgorithm(Lattice lattice, double costLimit, double minCostBenefitRatio, int aggregateLimit)

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.pentaho.aggdes.algorithm.Algorithm

computeAggregateCosts, run

Field Detail

parameterList

protected final List<Parameter> parameterList

schema

protected Schema schema

Constructor Detail

AlgorithmImpl

protected AlgorithmImpl()

Creates an AggregateTableAdvisorImpl

Method Detail

cancel

public void cancel()

Description copied from interface: Algorithm

Cancels a run.

Call this method from another thread.

Some algorithms are able to return a result if they are canceled before they run to completion; if so, the Algorithm.run(org.pentaho.aggdes.model.Schema, java.util.Map<org.pentaho.aggdes.model.Parameter, java.lang.Object>, org.pentaho.aggdes.algorithm.Progress) method will return that result; otherwise Algorithm.run(org.pentaho.aggdes.model.Schema, java.util.Map<org.pentaho.aggdes.model.Parameter, java.lang.Object>, org.pentaho.aggdes.algorithm.Progress) returns null.

Specified by:

cancel in interface Algorithm

getName

public String getName()

Description copied from interface: Component

Returns a name for this component.

Specified by:

getName in interface Component

Returns:

name for this component

getBaseName

public static String getBaseName(Class<? extends Component> aClass)

getParameters

public List<Parameter> getParameters()

Description copied from interface: Component

Declares the parameters that this component accepts.

Specified by:

getParameters in interface Component

Returns:

list of parameters that this component accepts

onStart

protected void onStart(Map<Parameter,Object> parameterValues,
           Progress progress)

Called by the Algorithm.run(org.pentaho.aggdes.model.Schema, java.util.Map<org.pentaho.aggdes.model.Parameter, java.lang.Object>, org.pentaho.aggdes.algorithm.Progress) method, resets the 'canceled' flag and sets the start time for timeout purposes.

Parameters:

parameterValues - Parameters

progress - Progress callback

checkCancelTimeout

protected boolean checkCancelTimeout()

Checks whether this algorithm has been canceled or has exceeded its maximum running time.

Algorithm must call this method regularly and terminate if it returns true.

Returns:

whether algorithm needs to terminate due to either cancelation or timeout

createAggregate

public Aggregate createAggregate(Schema schema,
                        List<Attribute> attributeList)

Description copied from interface: Algorithm

Creates an Aggregate.

Specified by:

createAggregate in interface Algorithm

Parameters:

schema - Schema object

attributeList - List of attributes

Returns:

Aggregate

runAlgorithm

protected ResultImpl runAlgorithm(Lattice lattice,
                      double costLimit,
                      double minCostBenefitRatio,
                      int aggregateLimit)