com.googlecode.javaewah
Class EWAHCompressedBitmap

java.lang.Object
  com.googlecode.javaewah.EWAHCompressedBitmap

All Implemented Interfaces:

BitmapStorage, LogicalElement<EWAHCompressedBitmap>, Externalizable, Serializable, Cloneable, Iterable<Integer>

public final class EWAHCompressedBitmap
extends Object
implements Cloneable, Externalizable, Iterable<Integer>, BitmapStorage, LogicalElement<EWAHCompressedBitmap>

This implements the patent-free(1) EWAH scheme. Roughly speaking, it is a 64-bit variant of the BBC compression scheme used by Oracle for its bitmap indexes.

The objective of this compression type is to provide some compression, while reducing as much as possible the CPU cycle usage.

Once constructed, the bitmap is essentially immutable (unless you call the "set" or "add" methods). Thus, it can be safely used in multi-threaded programs.

This implementation being 64-bit, it assumes a 64-bit CPU together with a 64-bit Java Virtual Machine. This same code on a 32-bit machine may not be as fast. There is also a 32-bit version of this code in the class javaewah32.EWAHCompressedBitmap32.

Here is a code sample to illustrate usage:

 EWAHCompressedBitmap ewahBitmap1 = EWAHCompressedBitmap.bitmapOf(0, 2, 55, 64,
         1 << 30);
 EWAHCompressedBitmap ewahBitmap2 = EWAHCompressedBitmap.bitmapOf(1, 3, 64,
         1 << 30);
 EWAHCompressedBitmap ewahBitmap3 = EWAHCompressedBitmap
         .bitmapOf(5, 55, 1 << 30);
 EWAHCompressedBitmap ewahBitmap4 = EWAHCompressedBitmap
         .bitmapOf(4, 66, 1 << 30);
 EWAHCompressedBitmap orbitmap = ewahBitmap1.or(ewahBitmap2);
 EWAHCompressedBitmap andbitmap = ewahBitmap1.and(ewahBitmap2);
 EWAHCompressedBitmap xorbitmap = ewahBitmap1.xor(ewahBitmap2);
 andbitmap = EWAHCompressedBitmap.and(ewahBitmap1, ewahBitmap2, ewahBitmap3,
         ewahBitmap4);
 ByteArrayOutputStream bos = new ByteArrayOutputStream();
 ObjectOutputStream oo = new ObjectOutputStream(bos);
 ewahBitmap1.writeExternal(oo);
 oo.close();
 ewahBitmap1 = null;
 ewahBitmap1 = new EWAHCompressedBitmap();
 ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
 ewahBitmap1.readExternal(new ObjectInputStream(bis));
 EWAHCompressedBitmap threshold2 = EWAHCompressedBitmap.threshold(2,
         ewahBitmap1, ewahBitmap2, ewahBitmap3, ewahBitmap4);
 

For more details, see the following papers:

• Daniel Lemire, Owen Kaser, Kamel Aouiche, Sorting improves word-aligned bitmap indexes. Data & Knowledge Engineering 69 (1), pages 3-28, 2010. http://arxiv.org/abs/0901.3751
• Owen Kaser and Daniel Lemire, Compressed bitmap indexes: beyond unions and intersections http://arxiv.org/abs/1402.4466

A 32-bit version of the compressed format was described by Wu et al. and named WBC:

• K. Wu, E. J. Otoo, A. Shoshani, H. Nordberg, Notes on design and implementation of compressed bit vectors, Tech. Rep. LBNL/PUB-3161, Lawrence Berkeley National Laboratory, available from http://crd.lbl. gov/~kewu/ps/PUB-3161.html (2001).

Probably, the best prior art is the Oracle bitmap compression scheme (BBC):

• G. Antoshenkov, Byte-Aligned Bitmap Compression, DCC'95, 1995.

1- The authors do not know of any patent infringed by the following implementation. However, similar schemes, like WAH are covered by patents.

Since:

0.1.0

See Also:

EWAHCompressedBitmap32, Serialized Form

Field Summary

static boolean	adjustContainerSizeWhenAggregating whether we adjust after some aggregation by adding in zeroes
static int	wordinbits The Constant wordinbits represents the number of bits in a long.

Constructor Summary

EWAHCompressedBitmap()
Creates an empty bitmap (no bit set to true).

EWAHCompressedBitmap(int buffersize)
Sets explicitly the buffer size (in 64-bit words).

Method Summary

void	add(long newdata) Deprecated. use addWord() instead.
void	add(long newdata, int bitsthatmatter) Deprecated. use addWord() instead.
void	addStreamOfEmptyWords(boolean v, long number) For experts: You want to add many zeroes or ones? This is the method you use.
void	addStreamOfLiteralWords(long[] data, int start, int number) if you have several literal words to copy over, this might be faster.
void	addStreamOfNegatedLiteralWords(long[] data, int start, int number) Same as addStreamOfLiteralWords, but the words are negated.
void	addWord(long newdata) Adding words directly to the bitmap (for expert use).
void	addWord(long newdata, int bitsthatmatter) Adding words directly to the bitmap (for expert use).
static EWAHCompressedBitmap	and(EWAHCompressedBitmap... bitmaps) Returns a new compressed bitmap containing the bitwise AND values of the provided bitmaps.
EWAHCompressedBitmap	and(EWAHCompressedBitmap a) Returns a new compressed bitmap containing the bitwise AND values of the current bitmap with some other bitmap.
static int	andCardinality(EWAHCompressedBitmap... bitmaps) Returns the cardinality of the result of a bitwise AND of the values of the provided bitmaps.
int	andCardinality(EWAHCompressedBitmap a) Returns the cardinality of the result of a bitwise AND of the values of the current bitmap with some other bitmap.
EWAHCompressedBitmap	andNot(EWAHCompressedBitmap a) Returns a new compressed bitmap containing the bitwise AND NOT values of the current bitmap with some other bitmap.
int	andNotCardinality(EWAHCompressedBitmap a) Returns the cardinality of the result of a bitwise AND NOT of the values of the current bitmap with some other bitmap.
void	andNotToContainer(EWAHCompressedBitmap a, BitmapStorage container) Returns a new compressed bitmap containing the bitwise AND NOT values of the current bitmap with some other bitmap.
void	andToContainer(EWAHCompressedBitmap a, BitmapStorage container) Computes new compressed bitmap containing the bitwise AND values of the current bitmap with some other bitmap.
static void	andWithContainer(BitmapStorage container, EWAHCompressedBitmap... bitmaps) For internal use.
static EWAHCompressedBitmap	bitmapOf(int... setbits) Return a bitmap with the bit set to true at the given positions.
int	cardinality() reports the number of bits set to true.
void	clear() Clear any set bits and set size in bits back to 0
IntIterator	clearIntIterator() Iterator over the clear bits.
EWAHCompressedBitmap	clone()
void	deserialize(DataInput in) Deserialize.
boolean	equals(Object o) Check to see whether the two compressed bitmaps contain the same set bits.
boolean	get(int i) Query the value of a single bit.
EWAHIterator	getEWAHIterator() Gets an EWAHIterator over the data.
IteratingRLW	getIteratingRLW() Gets an IteratingRLW to iterate over the data.
List<Integer>	getPositions() Deprecated. use toList() instead.
int	hashCode() Returns a customized hash code (based on Karp-Rabin).
boolean	intersects(EWAHCompressedBitmap a) Return true if the two EWAHCompressedBitmap have both at least one true bit in the same position.
IntIterator	intIterator() Iterator over the set bits (this is what most people will want to use to browse the content if they want an iterator).
Iterator<Integer>	iterator() Iterates over the positions of the true values.
void	not() Negate (bitwise) the current bitmap.
static EWAHCompressedBitmap	or(EWAHCompressedBitmap... bitmaps) Returns a new compressed bitmap containing the bitwise OR values of the provided bitmaps.
EWAHCompressedBitmap	or(EWAHCompressedBitmap a) Returns a new compressed bitmap containing the bitwise OR values of the current bitmap with some other bitmap.
static int	orCardinality(EWAHCompressedBitmap... bitmaps) Returns the cardinality of the result of a bitwise OR of the values of the provided bitmaps.
int	orCardinality(EWAHCompressedBitmap a) Returns the cardinality of the result of a bitwise OR of the values of the current bitmap with some other bitmap.
void	orToContainer(EWAHCompressedBitmap a, BitmapStorage container) Computes the bitwise or between the current bitmap and the bitmap "a".
static void	orWithContainer(BitmapStorage container, EWAHCompressedBitmap... bitmaps) Uses an adaptive technique to compute the logical OR.
void	readExternal(ObjectInput in)
void	serialize(DataOutput out) Serialize.
int	serializedSizeInBytes() Report the size required to serialize this bitmap The current bitmap is not modified.
boolean	set(int i) Set the bit at position i to true, the bits must be set in (strictly) increasing order.
void	setSizeInBits(int size) Set the size in bits.
boolean	setSizeInBits(int size, boolean defaultvalue) Change the reported size in bits of the *uncompressed* bitmap represented by this compressed bitmap.
int	sizeInBits() Returns the size in bits of the *uncompressed* bitmap represented by this compressed bitmap.
int	sizeInBytes() Report the *compressed* size of the bitmap (equivalent to memory usage, after accounting for some overhead).
void	swap(EWAHCompressedBitmap other) Swap the content of the bitmap with another.
static EWAHCompressedBitmap	threshold(int T, EWAHCompressedBitmap... bitmaps) Compute a Boolean threshold function: bits are true where at least T bitmaps have a true bit.
static void	thresholdWithContainer(BitmapStorage container, int T, EWAHCompressedBitmap... bitmaps) Compute a Boolean threshold function: bits are true where at least T bitmaps have a true bit.
int[]	toArray() Populate an array of (sorted integers) corresponding to the location of the set bits.
String	toDebugString() A more detailed string describing the bitmap (useful for debugging).
List<Integer>	toList() Gets the locations of the true values as one list.
String	toString() A string describing the bitmap.
void	trim() Reduce the internal buffer to its minimal allowable size (given by this.actualsizeinwords).
void	writeExternal(ObjectOutput out)
static EWAHCompressedBitmap	xor(EWAHCompressedBitmap... bitmaps) Returns a new compressed bitmap containing the bitwise XOR values of the provided bitmaps.
EWAHCompressedBitmap	xor(EWAHCompressedBitmap a) Returns a new compressed bitmap containing the bitwise XOR values of the current bitmap with some other bitmap.
int	xorCardinality(EWAHCompressedBitmap a) Returns the cardinality of the result of a bitwise XOR of the values of the current bitmap with some other bitmap.
void	xorToContainer(EWAHCompressedBitmap a, BitmapStorage container) Computes a new compressed bitmap containing the bitwise XOR values of the current bitmap with some other bitmap.
static void	xorWithContainer(BitmapStorage container, EWAHCompressedBitmap... bitmaps) Uses an adaptive technique to compute the logical XOR.

Methods inherited from class java.lang.Object

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

Field Detail

adjustContainerSizeWhenAggregating

public static final boolean adjustContainerSizeWhenAggregating

whether we adjust after some aggregation by adding in zeroes

See Also:

Constant Field Values

wordinbits

public static final int wordinbits

The Constant wordinbits represents the number of bits in a long.

See Also:

Constant Field Values

Constructor Detail

EWAHCompressedBitmap

public EWAHCompressedBitmap()

Creates an empty bitmap (no bit set to true).

EWAHCompressedBitmap

public EWAHCompressedBitmap(int buffersize)

Sets explicitly the buffer size (in 64-bit words). The initial memory usage will be "buffersize * 64". For large poorly compressible bitmaps, using large values may improve performance.

Parameters:

buffersize - number of 64-bit words reserved when the object is created)

Method Detail

add

@Deprecated
public void add(long newdata)

Deprecated. use addWord() instead.

Parameters:

newdata - the word

add

@Deprecated
public void add(long newdata,
                           int bitsthatmatter)

Deprecated. use addWord() instead.

Parameters:

newdata - the word

bitsthatmatter - the number of significant bits (by default it should be 64)

addWord

public void addWord(long newdata)

Adding words directly to the bitmap (for expert use). This method adds bits in words of 4*8 bits. It is not to be confused with the set method which sets individual bits. Most users will want the set method. Example: if you add word 321 to an empty bitmap, you are have added (in binary notation) 0b101000001, so you have effectively called set(0), set(6), set(8) in sequence. Since this modifies the bitmap, this method is not thread-safe. API change: prior to version 0.8.3, this method was called add.

Specified by:

addWord in interface BitmapStorage

Parameters:

newdata - the word

addWord

public void addWord(long newdata,
                    int bitsthatmatter)

Adding words directly to the bitmap (for expert use). Since this modifies the bitmap, this method is not thread-safe. API change: prior to version 0.8.3, this method was called add.

Parameters:

newdata - the word

bitsthatmatter - the number of significant bits (by default it should be 64)

addStreamOfLiteralWords

public void addStreamOfLiteralWords(long[] data,
                                    int start,
                                    int number)

if you have several literal words to copy over, this might be faster. Since this modifies the bitmap, this method is not thread-safe.

Specified by:

addStreamOfLiteralWords in interface BitmapStorage

Parameters:

data - the literal words

start - the starting point in the array

number - the number of literal words to add

addStreamOfEmptyWords

public void addStreamOfEmptyWords(boolean v,
                                  long number)

For experts: You want to add many zeroes or ones? This is the method you use. Since this modifies the bitmap, this method is not thread-safe.

Specified by:

addStreamOfEmptyWords in interface BitmapStorage

Parameters:

v - the boolean value

number - the number

addStreamOfNegatedLiteralWords

public void addStreamOfNegatedLiteralWords(long[] data,
                                           int start,
                                           int number)

Same as addStreamOfLiteralWords, but the words are negated. Since this modifies the bitmap, this method is not thread-safe.

Specified by:

addStreamOfNegatedLiteralWords in interface BitmapStorage

Parameters:

data - the literal words

start - the starting point in the array

number - the number of literal words to add

and

public EWAHCompressedBitmap and(EWAHCompressedBitmap a)

Returns a new compressed bitmap containing the bitwise AND values of the current bitmap with some other bitmap. The running time is proportional to the sum of the compressed sizes (as reported by sizeInBytes()). If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage. The current bitmap is not modified.

Specified by:

and in interface LogicalElement<EWAHCompressedBitmap>

Parameters:

a - the other bitmap (it will not be modified)

Returns:

the EWAH compressed bitmap

Since:

0.4.3

andToContainer

public void andToContainer(EWAHCompressedBitmap a,
                           BitmapStorage container)

Computes new compressed bitmap containing the bitwise AND values of the current bitmap with some other bitmap. The running time is proportional to the sum of the compressed sizes (as reported by sizeInBytes()). The current bitmap is not modified. The content of the container is overwritten.

Parameters:

a - the other bitmap (it will not be modified)

container - where we store the result

Since:

0.4.0

andCardinality

public int andCardinality(EWAHCompressedBitmap a)

Returns the cardinality of the result of a bitwise AND of the values of the current bitmap with some other bitmap. Avoids allocating an intermediate bitmap to hold the result of the OR. The current bitmap is not modified.

Parameters:

a - the other bitmap (it will not be modified)

Returns:

the cardinality

Since:

0.4.0

andNot

public EWAHCompressedBitmap andNot(EWAHCompressedBitmap a)

Returns a new compressed bitmap containing the bitwise AND NOT values of the current bitmap with some other bitmap. The running time is proportional to the sum of the compressed sizes (as reported by sizeInBytes()). If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage. The current bitmap is not modified.

Specified by:

andNot in interface LogicalElement<EWAHCompressedBitmap>

Parameters:

a - the other bitmap (it will not be modified)

Returns:

the EWAH compressed bitmap

andNotToContainer

public void andNotToContainer(EWAHCompressedBitmap a,
                              BitmapStorage container)

Returns a new compressed bitmap containing the bitwise AND NOT values of the current bitmap with some other bitmap. This method is expected to be faster than doing A.and(B.clone().not()). The running time is proportional to the sum of the compressed sizes (as reported by sizeInBytes()). The current bitmap is not modified. The content of the container is overwritten.

Parameters:

a - the other bitmap (it will not be modified)

container - where to store the result

Since:

0.4.0

andNotCardinality

public int andNotCardinality(EWAHCompressedBitmap a)

Returns the cardinality of the result of a bitwise AND NOT of the values of the current bitmap with some other bitmap. Avoids allocating an intermediate bitmap to hold the result of the OR. The current bitmap is not modified.

Parameters:

a - the other bitmap (it will not be modified)

Returns:

the cardinality

Since:

0.4.0

cardinality

public int cardinality()

reports the number of bits set to true. Running time is proportional to compressed size (as reported by sizeInBytes).

Returns:

the number of bits set to true

clear

public void clear()

Clear any set bits and set size in bits back to 0

Specified by:

clear in interface BitmapStorage

clone

public EWAHCompressedBitmap clone()

Overrides:

clone in class Object

deserialize

public void deserialize(DataInput in)
                 throws IOException

Deserialize.

Parameters:

in - the DataInput stream

Throws:

IOException - Signals that an I/O exception has occurred.

equals

public boolean equals(Object o)

Check to see whether the two compressed bitmaps contain the same set bits.

Overrides:

equals in class Object

See Also:

Object.equals(java.lang.Object)

getEWAHIterator

public EWAHIterator getEWAHIterator()

Gets an EWAHIterator over the data. This is a customized iterator which iterates over run length words. For experts only. The current bitmap is not modified.

Returns:

the EWAHIterator

getIteratingRLW

public IteratingRLW getIteratingRLW()

Gets an IteratingRLW to iterate over the data. For experts only. The current bitmap is not modified.

Returns:

the IteratingRLW iterator corresponding to this bitmap

getPositions

@Deprecated
public List<Integer> getPositions()

Deprecated. use toList() instead.

Returns:

a list

toList

public List<Integer> toList()

Gets the locations of the true values as one list. (May use more memory than iterator().) The current bitmap is not modified. API change: prior to version 0.8.3, this method was called getPositions.

Returns:

the positions in a list

hashCode

public int hashCode()

Returns a customized hash code (based on Karp-Rabin). Naturally, if the bitmaps are equal, they will hash to the same value. The current bitmap is not modified.

Overrides:

hashCode in class Object

intersects

public boolean intersects(EWAHCompressedBitmap a)

Return true if the two EWAHCompressedBitmap have both at least one true bit in the same position. Equivalently, you could call "and" and check whether there is a set bit, but intersects will run faster if you don't need the result of the "and" operation. The current bitmap is not modified.

Parameters:

a - the other bitmap (it will not be modified)

Returns:

whether they intersect

Since:

0.3.2

intIterator

public IntIterator intIterator()

Iterator over the set bits (this is what most people will want to use to browse the content if they want an iterator). The location of the set bits is returned, in increasing order. The current bitmap is not modified.

Returns:

the int iterator

clearIntIterator

public IntIterator clearIntIterator()

Iterator over the clear bits. The location of the clear bits is returned, in increasing order. The current bitmap is not modified.

Returns:

the int iterator

iterator

public Iterator<Integer> iterator()

Iterates over the positions of the true values. This is similar to intIterator(), but it uses Java generics. The current bitmap is not modified.

Specified by:

iterator in interface Iterable<Integer>

Returns:

the iterator

not

public void not()

Negate (bitwise) the current bitmap. To get a negated copy, do EWAHCompressedBitmap x= ((EWAHCompressedBitmap) mybitmap.clone()); x.not(); The running time is proportional to the compressed size (as reported by sizeInBytes()). Because this modifies the bitmap, this method is not thread-safe.

Specified by:

not in interface LogicalElement<EWAHCompressedBitmap>

or

public EWAHCompressedBitmap or(EWAHCompressedBitmap a)

Returns a new compressed bitmap containing the bitwise OR values of the current bitmap with some other bitmap. The running time is proportional to the sum of the compressed sizes (as reported by sizeInBytes()). If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage. The current bitmap is not modified.

Specified by:

or in interface LogicalElement<EWAHCompressedBitmap>

Parameters:

a - the other bitmap (it will not be modified)

Returns:

the EWAH compressed bitmap

orToContainer

public void orToContainer(EWAHCompressedBitmap a,
                          BitmapStorage container)

Computes the bitwise or between the current bitmap and the bitmap "a". Stores the result in the container. The current bitmap is not modified. The content of the container is overwritten.

Parameters:

a - the other bitmap (it will not be modified)

container - where we store the result

Since:

0.4.0

orCardinality

public int orCardinality(EWAHCompressedBitmap a)

Returns the cardinality of the result of a bitwise OR of the values of the current bitmap with some other bitmap. Avoids allocating an intermediate bitmap to hold the result of the OR. The current bitmap is not modified.

Parameters:

a - the other bitmap (it will not be modified)

Returns:

the cardinality

Since:

0.4.0

readExternal

public void readExternal(ObjectInput in)
                  throws IOException

Specified by:

readExternal in interface Externalizable

Throws:

IOException

serialize

public void serialize(DataOutput out)
               throws IOException

Serialize. The current bitmap is not modified.

Parameters:

out - the DataOutput stream

Throws:

IOException - Signals that an I/O exception has occurred.

serializedSizeInBytes

public int serializedSizeInBytes()

Report the size required to serialize this bitmap The current bitmap is not modified.

Returns:

the size in bytes

get

public boolean get(int i)

Query the value of a single bit. Relying on this method when speed is needed is discouraged. The complexity is linear with the size of the bitmap. (This implementation is based on zhenjl's Go version of JavaEWAH.) The current bitmap is not modified.

Parameters:

i - the bit we are interested in

Returns:

whether the bit is set to true

set

public boolean set(int i)

Set the bit at position i to true, the bits must be set in (strictly) increasing order. For example, set(15) and then set(7) will fail. You must do set(7) and then set(15). Since this modifies the bitmap, this method is not thread-safe.

Parameters:

i - the index

Returns:

true if the value was set (always true when i greater or equal to sizeInBits()).

Throws:

IndexOutOfBoundsException - if i is negative or greater than Integer.MAX_VALUE - 64

setSizeInBits

public void setSizeInBits(int size)

Set the size in bits. This does not change the compressed bitmap.

Specified by:

setSizeInBits in interface BitmapStorage

Parameters:

size - number of bits

Since:

0.4.0

setSizeInBits

public boolean setSizeInBits(int size,
                             boolean defaultvalue)

Change the reported size in bits of the *uncompressed* bitmap represented by this compressed bitmap. It may change the underlying compressed bitmap. It is not possible to reduce the sizeInBits, but it can be extended. The new bits are set to false or true depending on the value of defaultvalue. This method is not thread-safe.

Parameters:

size - the size in bits

defaultvalue - the default boolean value

Returns:

true if the update was possible

sizeInBits

public int sizeInBits()

Returns the size in bits of the *uncompressed* bitmap represented by this compressed bitmap. Initially, the sizeInBits is zero. It is extended automatically when you set bits to true. The current bitmap is not modified.

Specified by:

sizeInBits in interface LogicalElement<EWAHCompressedBitmap>

Returns:

the size in bits

sizeInBytes

public int sizeInBytes()

Report the *compressed* size of the bitmap (equivalent to memory usage, after accounting for some overhead).

Specified by:

sizeInBytes in interface LogicalElement<EWAHCompressedBitmap>

Returns:

the size in bytes

threshold

public static EWAHCompressedBitmap threshold(int T,
                                             EWAHCompressedBitmap... bitmaps)

Compute a Boolean threshold function: bits are true where at least T bitmaps have a true bit.

Parameters:

T - the threshold

bitmaps - input data

Returns:

the aggregated bitmap

Since:

0.8.1

thresholdWithContainer

public static void thresholdWithContainer(BitmapStorage container,
                                          int T,
                                          EWAHCompressedBitmap... bitmaps)

Compute a Boolean threshold function: bits are true where at least T bitmaps have a true bit. The content of the container is overwritten.

Parameters:

T - the threshold

bitmaps - input data

container - where we write the aggregated bitmap

Since:

0.8.1

toArray

public int[] toArray()

Populate an array of (sorted integers) corresponding to the location of the set bits.

Returns:

the array containing the location of the set bits

toDebugString

public String toDebugString()

A more detailed string describing the bitmap (useful for debugging).

Returns:

the string

toString

public String toString()

A string describing the bitmap.

Overrides:

toString in class Object

Returns:

the string

swap

public void swap(EWAHCompressedBitmap other)

Swap the content of the bitmap with another.

Parameters:

other - bitmap to swap with

trim

public void trim()

Reduce the internal buffer to its minimal allowable size (given by this.actualsizeinwords). This can free memory.

writeExternal

public void writeExternal(ObjectOutput out)
                   throws IOException

Specified by:

writeExternal in interface Externalizable

Throws:

IOException

xor

public EWAHCompressedBitmap xor(EWAHCompressedBitmap a)

Returns a new compressed bitmap containing the bitwise XOR values of the current bitmap with some other bitmap. The running time is proportional to the sum of the compressed sizes (as reported by sizeInBytes()). If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage. The current bitmap is not modified.

Specified by:

xor in interface LogicalElement<EWAHCompressedBitmap>

Parameters:

a - the other bitmap (it will not be modified)

Returns:

the EWAH compressed bitmap

xorToContainer

public void xorToContainer(EWAHCompressedBitmap a,
                           BitmapStorage container)

Computes a new compressed bitmap containing the bitwise XOR values of the current bitmap with some other bitmap. The running time is proportional to the sum of the compressed sizes (as reported by sizeInBytes()). The current bitmap is not modified. The content of the container is overwritten.

Parameters:

a - the other bitmap (it will not be modified)

container - where we store the result

Since:

0.4.0

xorCardinality

public int xorCardinality(EWAHCompressedBitmap a)

Returns the cardinality of the result of a bitwise XOR of the values of the current bitmap with some other bitmap. Avoids allocating an intermediate bitmap to hold the result of the OR. The current bitmap is not modified.

Parameters:

a - the other bitmap (it will not be modified)

Returns:

the cardinality

Since:

0.4.0

andWithContainer

public static void andWithContainer(BitmapStorage container,
                                    EWAHCompressedBitmap... bitmaps)

For internal use. Computes the bitwise and of the provided bitmaps and stores the result in the container. The content of the container is overwritten.

Parameters:

container - where the result is stored

bitmaps - bitmaps to AND

Since:

0.4.3

and

public static EWAHCompressedBitmap and(EWAHCompressedBitmap... bitmaps)

Returns a new compressed bitmap containing the bitwise AND values of the provided bitmaps. It may or may not be faster than doing the aggregation two-by-two (A.and(B).and(C)). If only one bitmap is provided, it is returned as is. If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage.

Parameters:

bitmaps - bitmaps to AND together

Returns:

result of the AND

Since:

0.4.3

andCardinality

public static int andCardinality(EWAHCompressedBitmap... bitmaps)

Returns the cardinality of the result of a bitwise AND of the values of the provided bitmaps. Avoids allocating an intermediate bitmap to hold the result of the AND.

Parameters:

bitmaps - bitmaps to AND

Returns:

the cardinality

Since:

0.4.3

bitmapOf

public static EWAHCompressedBitmap bitmapOf(int... setbits)

Return a bitmap with the bit set to true at the given positions. The positions should be given in sorted order. (This is a convenience method.)

Parameters:

setbits - list of set bit positions

Returns:

the bitmap

Since:

0.4.5

orWithContainer

public static void orWithContainer(BitmapStorage container,
                                   EWAHCompressedBitmap... bitmaps)

Uses an adaptive technique to compute the logical OR. Mostly for internal use. The content of the container is overwritten.

Parameters:

container - where the aggregate is written.

bitmaps - to be aggregated

xorWithContainer

public static void xorWithContainer(BitmapStorage container,
                                    EWAHCompressedBitmap... bitmaps)

Uses an adaptive technique to compute the logical XOR. Mostly for internal use. The content of the container is overwritten.

Parameters:

container - where the aggregate is written.

bitmaps - to be aggregated

or

public static EWAHCompressedBitmap or(EWAHCompressedBitmap... bitmaps)

Returns a new compressed bitmap containing the bitwise OR values of the provided bitmaps. This is typically faster than doing the aggregation two-by-two (A.or(B).or(C).or(D)). If only one bitmap is provided, it is returned as is. If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage.

Parameters:

bitmaps - bitmaps to OR together

Returns:

result of the OR

Since:

0.4.0

xor

public static EWAHCompressedBitmap xor(EWAHCompressedBitmap... bitmaps)

Returns a new compressed bitmap containing the bitwise XOR values of the provided bitmaps. This is typically faster than doing the aggregation two-by-two (A.xor(B).xor(C).xor(D)). If only one bitmap is provided, it is returned as is. If you are not planning on adding to the resulting bitmap, you may call the trim() method to reduce memory usage.

Parameters:

bitmaps - bitmaps to XOR together

Returns:

result of the XOR

orCardinality

public static int orCardinality(EWAHCompressedBitmap... bitmaps)

Returns the cardinality of the result of a bitwise OR of the values of the provided bitmaps. Avoids allocating an intermediate bitmap to hold the result of the OR.

Parameters:

bitmaps - bitmaps to OR

Returns:

the cardinality

Since:

0.4.0