pegasus.mapreduce.common.types

Class BitStrings

java.lang.Object

pegasus.mapreduce.common.types.BitStrings

All Implemented Interfaces:

org.apache.hadoop.io.Writable

public class BitStrings
extends java.lang.Object
implements org.apache.hadoop.io.Writable

Represents multiple (typically, 32) bitstrings.

Constructor Summary

Constructors

Constructor and Description
BitStrings() Construct bitstrings with empty values.
BitStrings(long[] bits) Construct bitstring with given bit values.

Method Summary

Modifier and Type	Method and Description
double	cardinality() Returns the cardinality of bitstrings using Flajolet-Martin method.
boolean	equals(java.lang.Object o)
long	getBit(int i) Returns i-th sub-bitstring.
long[]	getBits() Returns current bit values.
int	hashCode()
boolean	isEmpty() Returns whether all bitstrings are empty or not.
void	or(BitStrings other) Applies bitwise-or operation on itself and the given bitstrings and assigns the result of operation.
void	readFields(java.io.DataInput in) Read bitstring values from an input stream.
void	setBit(int i, long bit) Sets i-th sub-bitstring to the given bit values.
void	setBits(long[] bits) Sets the value of bitstring to the given bit values.
java.lang.String	toString()
void	write(java.io.DataOutput out) Writes bitstring values to an output stream.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

BitStrings

public BitStrings()

Construct bitstrings with empty values.

BitStrings

public BitStrings(long[] bits)

Construct bitstring with given bit values.

Parameters:

bits - The initial bit values

Method Detail

setBits

public void setBits(long[] bits)

Sets the value of bitstring to the given bit values.

Parameters:

bits - The bit values to be set

getBits

public long[] getBits()

Returns current bit values.

Returns:

The current bit values which are stored

getBit

public long getBit(int i)

Returns i-th sub-bitstring.

Parameters:

i - The index of desired bitstring

Returns:

The i-th sub-bitstring

setBit

public void setBit(int i,
                   long bit)

Sets i-th sub-bitstring to the given bit values.

Parameters:

i - The index of bitstring to be updated

bit - The bit values

or

public void or(BitStrings other)

Applies bitwise-or operation on itself and the given bitstrings and assigns the result of operation.

Parameters:

other - The bitstrings for bitwise-or operation

isEmpty

public boolean isEmpty()

Returns whether all bitstrings are empty or not.

Returns:

true if all bitstrings are empty, otherwise false

write

public void write(java.io.DataOutput out)
           throws java.io.IOException

Writes bitstring values to an output stream.

Specified by:

write in interface org.apache.hadoop.io.Writable

Parameters:

out - The output stream object to write the values

Throws:

java.io.IOException

readFields

public void readFields(java.io.DataInput in)
                throws java.io.IOException

Read bitstring values from an input stream.

Specified by:

readFields in interface org.apache.hadoop.io.Writable

Parameters:

in - The input stream object to read the values

Throws:

java.io.IOException

equals

public boolean equals(java.lang.Object o)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

cardinality

public double cardinality()

Returns the cardinality of bitstrings using Flajolet-Martin method.

Returns:

The cardinality of bitstrings

See Also:

Wikipedia, Probabitistic Counting Algorithms for Data Base Applications

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object