Package org.apache.lucene.util
Class OpenBitSet
- java.lang.Object
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- org.apache.lucene.search.DocIdSet
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- org.apache.lucene.util.OpenBitSet
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- All Implemented Interfaces:
java.lang.Cloneable
,Bits
- Direct Known Subclasses:
OpenBitSetDISI
public class OpenBitSet extends DocIdSet implements Bits, java.lang.Cloneable
An "open" BitSet implementation that allows direct access to the array of words storing the bits. Unlike java.util.bitset, the fact that bits are packed into an array of longs is part of the interface. This allows efficient implementation of other algorithms by someone other than the author. It also allows one to efficiently implement alternate serialization or interchange formats.OpenBitSet
is faster thanjava.util.BitSet
in most operations and *much* faster at calculating cardinality of sets and results of set operations. It can also handle sets of larger cardinality (up to 64 * 2**32-1) The goals ofOpenBitSet
are the fastest implementation possible, and maximum code reuse. Extra safety and encapsulation may always be built on top, but if that's built in, the cost can never be removed (and hence people re-implement their own version in order to get better performance). If you want a "safe", totally encapsulated (and slower and limited) BitSet class, usejava.util.BitSet
.Performance Results
Test system: Pentium 4, Sun Java 1.5_06 -server -Xbatch -Xmx64M
BitSet size = 1,000,000
Results are java.util.BitSet time divided by OpenBitSet time.cardinality intersect_count union nextSetBit get iterator 50% full 3.36 3.96 1.44 1.46 1.99 1.58 1% full 3.31 3.90 1.04 0.99
Test system: AMD Opteron, 64 bit linux, Sun Java 1.5_06 -server -Xbatch -Xmx64M
BitSet size = 1,000,000
Results are java.util.BitSet time divided by OpenBitSet time.cardinality intersect_count union nextSetBit get iterator 50% full 2.50 3.50 1.00 1.03 1.12 1.25 1% full 2.51 3.49 1.00 1.02
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Nested Class Summary
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Nested classes/interfaces inherited from interface org.apache.lucene.util.Bits
Bits.MatchAllBits, Bits.MatchNoBits
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Field Summary
Fields Modifier and Type Field Description protected long[]
bits
protected int
wlen
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Fields inherited from interface org.apache.lucene.util.Bits
EMPTY_ARRAY
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Constructor Summary
Constructors Constructor Description OpenBitSet()
Constructor: allocates enough space for 64 bits.OpenBitSet(long numBits)
Constructs an OpenBitSet large enough to holdnumBits
.OpenBitSet(long[] bits, int numWords)
Constructs an OpenBitSet from an existing long[].
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description void
and(OpenBitSet other)
void
andNot(OpenBitSet other)
static long
andNotCount(OpenBitSet a, OpenBitSet b)
Returns the popcount or cardinality of "a and not b" or "intersection(a, not(b))".Bits
bits()
Optionally provides aBits
interface for random access to matching documents.static int
bits2words(long numBits)
returns the number of 64 bit words it would take to hold numBitslong
capacity()
Returns the current capacity in bits (1 greater than the index of the last bit)long
cardinality()
void
clear(int startIndex, int endIndex)
Clears a range of bits.void
clear(long index)
clears a bit, allowing access beyond the current set size without changing the size.void
clear(long startIndex, long endIndex)
Clears a range of bits.OpenBitSet
clone()
void
ensureCapacity(long numBits)
Ensure that the long[] is big enough to hold numBits, expanding it if necessary.void
ensureCapacityWords(int numWords)
Expand the long[] with the size given as a number of words (64 bit longs).boolean
equals(java.lang.Object o)
returns true if both sets have the same bits setprotected int
expandingWordNum(long index)
void
fastClear(int index)
clears a bit.void
fastClear(long index)
clears a bit.void
fastFlip(int index)
flips a bit.void
fastFlip(long index)
flips a bit.boolean
fastGet(int index)
Returns true or false for the specified bit index.boolean
fastGet(long index)
Returns true or false for the specified bit index.void
fastSet(int index)
Sets the bit at the specified index.void
fastSet(long index)
Sets the bit at the specified index.void
flip(long index)
flips a bit, expanding the set size if necessaryvoid
flip(long startIndex, long endIndex)
Flips a range of bits, expanding the set size if necessaryboolean
flipAndGet(int index)
flips a bit and returns the resulting bit value.boolean
flipAndGet(long index)
flips a bit and returns the resulting bit value.boolean
get(int index)
Returns true or false for the specified bit index.boolean
get(long index)
Returns true or false for the specified bit indexboolean
getAndSet(int index)
Sets a bit and returns the previous value.boolean
getAndSet(long index)
Sets a bit and returns the previous value.int
getBit(int index)
returns 1 if the bit is set, 0 if not.long[]
getBits()
Expert: returns the long[] storing the bitsint
getNumWords()
Expert: gets the number of longs in the array that are in useint
hashCode()
void
intersect(OpenBitSet other)
this = this AND otherstatic long
intersectionCount(OpenBitSet a, OpenBitSet b)
Returns the popcount or cardinality of the intersection of the two sets.boolean
intersects(OpenBitSet other)
returns true if the sets have any elements in commonboolean
isCacheable()
This DocIdSet implementation is cacheable.boolean
isEmpty()
Returns true if there are no set bitsDocIdSetIterator
iterator()
Provides aDocIdSetIterator
to access the set.int
length()
Returns the number of bits in this setint
nextSetBit(int index)
Returns the index of the first set bit starting at the index specified.long
nextSetBit(long index)
Returns the index of the first set bit starting at the index specified.void
or(OpenBitSet other)
int
prevSetBit(int index)
Returns the index of the first set bit starting downwards at the index specified.long
prevSetBit(long index)
Returns the index of the first set bit starting downwards at the index specified.void
remove(OpenBitSet other)
Remove all elements set in other.void
set(long index)
sets a bit, expanding the set size if necessaryvoid
set(long startIndex, long endIndex)
Sets a range of bits, expanding the set size if necessarylong
size()
Returns the current capacity of this set.void
trimTrailingZeros()
Lowers numWords, the number of words in use, by checking for trailing zero words.void
union(OpenBitSet other)
this = this OR otherstatic long
unionCount(OpenBitSet a, OpenBitSet b)
Returns the popcount or cardinality of the union of the two sets.void
xor(OpenBitSet other)
this = this XOR otherstatic long
xorCount(OpenBitSet a, OpenBitSet b)
Returns the popcount or cardinality of the exclusive-or of the two sets.
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Constructor Detail
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OpenBitSet
public OpenBitSet(long numBits)
Constructs an OpenBitSet large enough to holdnumBits
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OpenBitSet
public OpenBitSet()
Constructor: allocates enough space for 64 bits.
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OpenBitSet
public OpenBitSet(long[] bits, int numWords)
Constructs an OpenBitSet from an existing long[].The first 64 bits are in long[0], with bit index 0 at the least significant bit, and bit index 63 at the most significant. Given a bit index, the word containing it is long[index/64], and it is at bit number index%64 within that word.
numWords are the number of elements in the array that contain set bits (non-zero longs). numWords should be <= bits.length, and any existing words in the array at position >= numWords should be zero.
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Method Detail
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iterator
public DocIdSetIterator iterator()
Description copied from class:DocIdSet
Provides aDocIdSetIterator
to access the set. This implementation can returnnull
if there are no docs that match.
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bits
public Bits bits()
Description copied from class:DocIdSet
Optionally provides aBits
interface for random access to matching documents.- Overrides:
bits
in classDocIdSet
- Returns:
null
, if thisDocIdSet
does not support random access. In contrast toDocIdSet.iterator()
, a return value ofnull
does not imply that no documents match the filter! The default implementation does not provide random access, so you only need to implement this method if your DocIdSet can guarantee random access to every docid in O(1) time without external disk access (asBits
interface cannot throwIOException
). This is generally true for bit sets likeFixedBitSet
, which return itself if they are used asDocIdSet
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isCacheable
public boolean isCacheable()
This DocIdSet implementation is cacheable.- Overrides:
isCacheable
in classDocIdSet
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capacity
public long capacity()
Returns the current capacity in bits (1 greater than the index of the last bit)
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size
public long size()
Returns the current capacity of this set. Included for compatibility. This is *not* equal tocardinality()
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length
public int length()
Description copied from interface:Bits
Returns the number of bits in this set
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isEmpty
public boolean isEmpty()
Returns true if there are no set bits
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getBits
public long[] getBits()
Expert: returns the long[] storing the bits
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getNumWords
public int getNumWords()
Expert: gets the number of longs in the array that are in use
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get
public boolean get(int index)
Returns true or false for the specified bit index.- Specified by:
get
in interfaceBits
- Parameters:
index
- index, should be non-negative and <Bits.length()
. The result of passing negative or out of bounds values is undefined by this interface, just don't do it!- Returns:
true
if the bit is set,false
otherwise.
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fastGet
public boolean fastGet(int index)
Returns true or false for the specified bit index. The index should be less than the OpenBitSet size
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get
public boolean get(long index)
Returns true or false for the specified bit index
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fastGet
public boolean fastGet(long index)
Returns true or false for the specified bit index. The index should be less than the OpenBitSet size.
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getBit
public int getBit(int index)
returns 1 if the bit is set, 0 if not. The index should be less than the OpenBitSet size
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set
public void set(long index)
sets a bit, expanding the set size if necessary
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fastSet
public void fastSet(int index)
Sets the bit at the specified index. The index should be less than the OpenBitSet size.
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fastSet
public void fastSet(long index)
Sets the bit at the specified index. The index should be less than the OpenBitSet size.
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set
public void set(long startIndex, long endIndex)
Sets a range of bits, expanding the set size if necessary- Parameters:
startIndex
- lower indexendIndex
- one-past the last bit to set
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expandingWordNum
protected int expandingWordNum(long index)
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fastClear
public void fastClear(int index)
clears a bit. The index should be less than the OpenBitSet size.
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fastClear
public void fastClear(long index)
clears a bit. The index should be less than the OpenBitSet size.
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clear
public void clear(long index)
clears a bit, allowing access beyond the current set size without changing the size.
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clear
public void clear(int startIndex, int endIndex)
Clears a range of bits. Clearing past the end does not change the size of the set.- Parameters:
startIndex
- lower indexendIndex
- one-past the last bit to clear
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clear
public void clear(long startIndex, long endIndex)
Clears a range of bits. Clearing past the end does not change the size of the set.- Parameters:
startIndex
- lower indexendIndex
- one-past the last bit to clear
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getAndSet
public boolean getAndSet(int index)
Sets a bit and returns the previous value. The index should be less than the OpenBitSet size.
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getAndSet
public boolean getAndSet(long index)
Sets a bit and returns the previous value. The index should be less than the OpenBitSet size.
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fastFlip
public void fastFlip(int index)
flips a bit. The index should be less than the OpenBitSet size.
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fastFlip
public void fastFlip(long index)
flips a bit. The index should be less than the OpenBitSet size.
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flip
public void flip(long index)
flips a bit, expanding the set size if necessary
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flipAndGet
public boolean flipAndGet(int index)
flips a bit and returns the resulting bit value. The index should be less than the OpenBitSet size.
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flipAndGet
public boolean flipAndGet(long index)
flips a bit and returns the resulting bit value. The index should be less than the OpenBitSet size.
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flip
public void flip(long startIndex, long endIndex)
Flips a range of bits, expanding the set size if necessary- Parameters:
startIndex
- lower indexendIndex
- one-past the last bit to flip
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cardinality
public long cardinality()
- Returns:
- the number of set bits
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intersectionCount
public static long intersectionCount(OpenBitSet a, OpenBitSet b)
Returns the popcount or cardinality of the intersection of the two sets. Neither set is modified.
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unionCount
public static long unionCount(OpenBitSet a, OpenBitSet b)
Returns the popcount or cardinality of the union of the two sets. Neither set is modified.
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andNotCount
public static long andNotCount(OpenBitSet a, OpenBitSet b)
Returns the popcount or cardinality of "a and not b" or "intersection(a, not(b))". Neither set is modified.
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xorCount
public static long xorCount(OpenBitSet a, OpenBitSet b)
Returns the popcount or cardinality of the exclusive-or of the two sets. Neither set is modified.
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nextSetBit
public int nextSetBit(int index)
Returns the index of the first set bit starting at the index specified. -1 is returned if there are no more set bits.
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nextSetBit
public long nextSetBit(long index)
Returns the index of the first set bit starting at the index specified. -1 is returned if there are no more set bits.
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prevSetBit
public int prevSetBit(int index)
Returns the index of the first set bit starting downwards at the index specified. -1 is returned if there are no more set bits.
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prevSetBit
public long prevSetBit(long index)
Returns the index of the first set bit starting downwards at the index specified. -1 is returned if there are no more set bits.
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clone
public OpenBitSet clone()
- Overrides:
clone
in classjava.lang.Object
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intersect
public void intersect(OpenBitSet other)
this = this AND other
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union
public void union(OpenBitSet other)
this = this OR other
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remove
public void remove(OpenBitSet other)
Remove all elements set in other. this = this AND_NOT other
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xor
public void xor(OpenBitSet other)
this = this XOR other
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and
public void and(OpenBitSet other)
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or
public void or(OpenBitSet other)
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andNot
public void andNot(OpenBitSet other)
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intersects
public boolean intersects(OpenBitSet other)
returns true if the sets have any elements in common
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ensureCapacityWords
public void ensureCapacityWords(int numWords)
Expand the long[] with the size given as a number of words (64 bit longs).
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ensureCapacity
public void ensureCapacity(long numBits)
Ensure that the long[] is big enough to hold numBits, expanding it if necessary.
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trimTrailingZeros
public void trimTrailingZeros()
Lowers numWords, the number of words in use, by checking for trailing zero words.
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bits2words
public static int bits2words(long numBits)
returns the number of 64 bit words it would take to hold numBits
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equals
public boolean equals(java.lang.Object o)
returns true if both sets have the same bits set- Overrides:
equals
in classjava.lang.Object
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hashCode
public int hashCode()
- Overrides:
hashCode
in classjava.lang.Object
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