org.apache.flink.api.java

Class IterativeDataSet<T>

java.lang.Object

org.apache.flink.api.java.DataSet<OUT>

org.apache.flink.api.java.operators.Operator<OUT,O>

org.apache.flink.api.java.operators.SingleInputOperator<T,T,IterativeDataSet<T>>

org.apache.flink.api.java.IterativeDataSet<T>

Type Parameters:

T - The data type of set that is the input and feedback of the iteration.

public class IterativeDataSet<T>
extends SingleInputOperator<T,T,IterativeDataSet<T>>

The IterativeDataSet represents the start of an iteration. It is created from the DataSet that represents the initial solution set via the DataSet.iterate(int) method.

See Also:

DataSet.iterate(int)

Method Summary

Methods

Modifier and Type	Method and Description
DataSet<T>	closeWith(DataSet<T> iterationResult) Closes the iteration.
DataSet<T>	closeWith(DataSet<T> iterationResult, DataSet<?> terminationCriterion) Closes the iteration and specifies a termination criterion.
AggregatorRegistry	getAggregators() Gets the registry for aggregators.
int	getMaxIterations() Gets the maximum number of iterations.
<X extends Value> IterativeDataSet<T>	registerAggregationConvergenceCriterion(String name, Aggregator<X> aggregator, ConvergenceCriterion<X> convergenceCheck) Registers an Aggregator for the iteration together with a ConvergenceCriterion.
IterativeDataSet<T>	registerAggregator(String name, Aggregator<?> aggregator) Registers an Aggregator for the iteration.
protected SingleInputOperator<T,T,?>	translateToDataFlow(Operator<T> input) Translates this operation to a data flow operator of the common data flow API.

Methods inherited from class org.apache.flink.api.java.operators.SingleInputOperator

getInput, getInputType

Methods inherited from class org.apache.flink.api.java.operators.Operator

getName, getParallelism, getResultType, name, setParallelism

Methods inherited from class org.apache.flink.api.java.DataSet

aggregate, checkSameExecutionContext, coGroup, cross, crossWithHuge, crossWithTiny, distinct, distinct, distinct, filter, flatMap, getExecutionEnvironment, getType, groupBy, groupBy, iterate, iterateDelta, join, joinWithHuge, joinWithTiny, map, max, min, output, print, printToErr, project, reduce, reduceGroup, runOperation, sum, union, write, write, writeAsCsv, writeAsCsv, writeAsCsv, writeAsText, writeAsText

Methods inherited from class java.lang.Object

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

Method Detail

closeWith

public DataSet<T> closeWith(DataSet<T> iterationResult)

Closes the iteration. This method defines the end of the iterative program part.

Parameters:

iterationResult - The data set that will be fed back to the next iteration.

Returns:

The DataSet that represents the result of the iteration, after the computation has terminated.

See Also:

DataSet.iterate(int)

closeWith

public DataSet<T> closeWith(DataSet<T> iterationResult,
                   DataSet<?> terminationCriterion)

Closes the iteration and specifies a termination criterion. This method defines the end of the iterative program part.

The termination criterion is a means of dynamically signaling the iteration to halt. It is expressed via a data set that will trigger to halt the loop as soon as the data set is empty. A typical way of using the termination criterion is to have a filter that filters out all elements that are considered non-converged. As soon as no more such elements exist, the iteration finishes.

Parameters:

iterationResult - The data set that will be fed back to the next iteration.

Returns:

The DataSet that represents the result of the iteration, after the computation has terminated.

See Also:

DataSet.iterate(int)

getMaxIterations

public int getMaxIterations()

Gets the maximum number of iterations.

Returns:

The maximum number of iterations.

registerAggregator

public IterativeDataSet<T> registerAggregator(String name,
                                     Aggregator<?> aggregator)

Registers an Aggregator for the iteration. Aggregators can be used to maintain simple statistics during the iteration, such as number of elements processed. The aggregators compute global aggregates: After each iteration step, the values are globally aggregated to produce one aggregate that represents statistics across all parallel instances. The value of an aggregator can be accessed in the next iteration.

Aggregators can be accessed inside a function via the AbstractRichFunction.getIterationRuntimeContext() method.

Parameters:

name - The name under which the aggregator is registered.

aggregator - The aggregator class.

Returns:

The IterativeDataSet itself, to allow chaining function calls.

registerAggregationConvergenceCriterion

public <X extends Value> IterativeDataSet<T> registerAggregationConvergenceCriterion(String name,
                                                                            Aggregator<X> aggregator,
                                                                            ConvergenceCriterion<X> convergenceCheck)

Registers an Aggregator for the iteration together with a ConvergenceCriterion. For a general description of aggregators, see registerAggregator(String, Aggregator) and Aggregator. At the end of each iteration, the convergence criterion takes the aggregator's global aggregate value and decided whether the iteration should terminate. A typical use case is to have an aggregator that sums up the total error of change in an iteration step and have to have a convergence criterion that signals termination as soon as the aggregate value is below a certain threshold.

Parameters:

name - The name under which the aggregator is registered.

aggregator - The aggregator class.

convergenceCheck - The convergence criterion.

Returns:

The IterativeDataSet itself, to allow chaining function calls.

getAggregators

public AggregatorRegistry getAggregators()

Gets the registry for aggregators. On the registry, one can add Aggregators and an aggregator-based ConvergenceCriterion. This method offers an alternative way to registering the aggregators via registerAggregator(String, Aggregator) and ).

Returns:

The registry for aggregators.

translateToDataFlow

protected SingleInputOperator<T,T,?> translateToDataFlow(Operator<T> input)

Description copied from class: SingleInputOperator

Translates this operation to a data flow operator of the common data flow API.

Specified by:

translateToDataFlow in class SingleInputOperator<T,T,IterativeDataSet<T>>

Parameters:

input - The data flow operator that produces this operation's input data.

Returns:

The translated data flow operator.