org.apache.hadoop.examples
Class PiEstimator

java.lang.Object
  org.apache.hadoop.conf.Configured
      org.apache.hadoop.examples.PiEstimator

All Implemented Interfaces:

Configurable, Tool

public class PiEstimator
extends Configured
implements 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

static class	PiEstimator.PiMapper Mapper class for Pi estimation.
static class	PiEstimator.PiReducer Reducer class for Pi estimation.

Constructor Summary

PiEstimator()

Method Summary

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

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 Tool

Parameters:

args - command specific arguments.

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