org.apache.hadoop.examples

Class PiEstimator

java.lang.Object

org.apache.hadoop.conf.Configured

org.apache.hadoop.examples.PiEstimator

All Implemented Interfaces:

org.apache.hadoop.conf.Configurable, org.apache.hadoop.util.Tool

public class PiEstimator
extends org.apache.hadoop.conf.Configured
implements org.apache.hadoop.util.Tool

A Map-reduce program to estimate the value of Pi using quasi-Monte Carlo method. Mapper: Generate points in a unit square and then count points inside/outside of the inscribed circle of the square. Reducer: Accumulate points inside/outside results from the mappers. Let numTotal = numInside + numOutside. The fraction numInside/numTotal is a rational approximation of the value (Area of the circle)/(Area of the square), where the area of the inscribed circle is Pi/4 and the area of unit square is 1. Then, Pi is estimated value to be 4(numInside/numTotal).

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	PiEstimator.PiMapper Mapper class for Pi estimation.
static class	PiEstimator.PiReducer Reducer class for Pi estimation.

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_PRECISION

Constructor Summary

Constructors

Constructor and Description
PiEstimator()

Method Summary

Methods

Modifier and Type	Method and Description
static BigDecimal	estimate(int numMaps, long numPoints, JobConf jobConf) Run a map/reduce job for estimating Pi.
static void	main(String[] argv) main method for running it as a stand alone command.
int	run(String[] args) Parse arguments and then runs a map/reduce job.

Methods inherited from class org.apache.hadoop.conf.Configured

getConf, setConf

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.hadoop.conf.Configurable

getConf, setConf

Field Detail

DEFAULT_PRECISION

public static int DEFAULT_PRECISION

Constructor Detail

PiEstimator

public PiEstimator()

Method Detail

estimate

public static BigDecimal estimate(int numMaps,
                  long numPoints,
                  JobConf jobConf)
                           throws IOException

Run a map/reduce job for estimating Pi.

Returns:

the estimated value of Pi

Throws:

IOException

run

public int run(String[] args)
        throws Exception

Parse arguments and then runs a map/reduce job. Print output in standard out.

Specified by:

run in interface org.apache.hadoop.util.Tool

Returns:

a non-zero if there is an error. Otherwise, return 0.

Throws:

Exception

main

public static void main(String[] argv)
                 throws Exception

main method for running it as a stand alone command.

Throws:

Exception