org.apache.hadoop.mapred
Class PeriodicStatsAccumulator

java.lang.Object
  org.apache.hadoop.mapred.PeriodicStatsAccumulator

@InterfaceAudience.Private
@InterfaceStability.Unstable
public abstract class PeriodicStatsAccumulator
extends Object

This abstract class that represents a bucketed series of measurements of a quantity being measured in a running task attempt.

The sole constructor is called with a count, which is the number of buckets into which we evenly divide the spectrum of progress from 0.0D to 1.0D . In the future we may provide for custom split points that don't have to be uniform.

A subclass determines how we fold readings for portions of a bucket and how we interpret the readings by overriding extendInternal(...) and initializeInterval()

Field Summary

protected int	count
protected int[]	values

Method Summary

protected void	advanceState(double newProgress, int newValue)
protected void	extend(double newProgress, int newValue) This method calls extendInternal at least once.
protected abstract void	extendInternal(double newProgress, int newValue) adds a new reading to the current bucket.
protected int[]	getValues()
protected void	initializeInterval() initializes the state variables to be ready for a new interval

Methods inherited from class java.lang.Object

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

Field Detail

count

protected final int count

values

protected final int[] values

Method Detail

getValues

protected int[] getValues()

extendInternal

protected abstract void extendInternal(double newProgress,
                                       int newValue)

adds a new reading to the current bucket.

Parameters:

newProgress - the endpoint of the interval this new reading covers

newValue - the value of the reading at newProgress The class has three instance variables, oldProgress and oldValue and currentAccumulation. extendInternal can count on three things: 1: The first time it's called in a particular instance, both oldXXX's will be zero. 2: oldXXX for a later call is the value of newXXX of the previous call. This ensures continuity in accumulation from one call to the next. 3: currentAccumulation is owned by initializeInterval and extendInternal.

initializeInterval

protected void initializeInterval()

initializes the state variables to be ready for a new interval

extend

protected void extend(double newProgress,
                      int newValue)

This method calls extendInternal at least once. It divides the current progress interval [from the last call's newProgress to this call's newProgress ] into one or more subintervals by splitting at any point which is an interval boundary if there are any such points. It then calls extendInternal for each subinterval, or the whole interval if there are no splitting points.

For example, if the value was 300 last time with 0.3 progress, and count is 5, and you get a new reading with the variable at 700 and progress at 0.7, you get three calls to extendInternal: one extending from progress 0.3 to 0.4 [the next boundary] with a value of 400, the next one through 0.6 with a value of 600, and finally one at 700 with a progress of 0.7 .

Parameters:

newProgress - the endpoint of the progress range this new reading covers

newValue - the value of the reading at newProgress

advanceState

protected void advanceState(double newProgress,
                            int newValue)