Package it.unimi.dsi.sux4j.mph
Class TwoStepsMWHCFunction<T>
java.lang.Object
it.unimi.dsi.fastutil.objects.AbstractObject2LongFunction<K>
it.unimi.dsi.sux4j.mph.AbstractHashFunction<T>
it.unimi.dsi.sux4j.mph.TwoStepsMWHCFunction<T>
- All Implemented Interfaces:
Function<T,
,Long> Object2LongFunction<T>
,Size64
,Serializable
,Function<T,
,Long> ToLongFunction<T>
@Deprecated
public class TwoStepsMWHCFunction<T>
extends AbstractHashFunction<T>
implements Serializable, Size64
Deprecated.
A function stored using two Majewski-Wormald-Havas-Czech
functions—one for frequent values, and one for infrequent values. This naive idea turns
out to be very effective in reducing the function size when the distribution of values is skewed
(e.g., as it happens in a
TwoStepsLcpMonotoneMinimalPerfectHashFunction
).
To create an instance, we perform a pre-scan of the values to be assigned. If possible, we finds
the best possible r such that the 2r − 1 most frequent
values can be stored in a MWHCFunction
and suitably remapped when read. The function uses
2r − 1 as an escape symbol for all other values, which are stored in
a separate function.
Warning: during the construction phase, a
filter will be set on the
ChunkedHashStore
used to store the keys. If you are
passing a store, you will have
to reset it to its previous state.
- Since:
- 1.0.2
- Author:
- Sebastiano Vigna
- See Also:
-
Nested Class Summary
Modifier and TypeClassDescriptionstatic class
Deprecated.A builder class forTwoStepsMWHCFunction
. -
Field Summary
Modifier and TypeFieldDescriptionprotected final int
Deprecated.The escape value returned byfirstFunction
to suggest thatsecondFunction
should be queried instead, provided that there is a first function.protected final MWHCFunction<T>
Deprecated.The first function, ornull
.protected final long
Deprecated.The number of keys.protected final double
Deprecated.The mean of the rank distribution.protected final long[]
Deprecated.A mapping from values of the first function to actual values, provided that there is a first function.protected final MWHCFunction<T>
Deprecated.The second function.protected long
Deprecated.The seed to be used when converting keys to triples.static final long
Deprecated.protected final TransformationStrategy<? super T>
Deprecated.The transformation strategy to turn objects of typeT
into bit vectors.protected final int
Deprecated.The width of the output of this function, in bits.Fields inherited from class it.unimi.dsi.fastutil.objects.AbstractObject2LongFunction
defRetValue
-
Constructor Summary
ModifierConstructorDescriptionprotected
TwoStepsMWHCFunction
(Iterable<? extends T> keys, TransformationStrategy<? super T> transform, LongBigList values, File tempDir, ChunkedHashStore<T> chunkedHashStore) Deprecated.Creates a new two-step function for the given keys and values. -
Method Summary
Methods inherited from class it.unimi.dsi.sux4j.mph.AbstractHashFunction
containsKey, size
Methods inherited from class it.unimi.dsi.fastutil.objects.AbstractObject2LongFunction
defaultReturnValue, defaultReturnValue
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods inherited from interface it.unimi.dsi.fastutil.objects.Object2LongFunction
andThen, andThenByte, andThenChar, andThenDouble, andThenFloat, andThenInt, andThenLong, andThenObject, andThenReference, andThenShort, applyAsLong, composeByte, composeChar, composeDouble, composeFloat, composeInt, composeLong, composeObject, composeReference, composeShort, get, getOrDefault, getOrDefault, put, put, remove, removeLong
-
Field Details
-
serialVersionUID
public static final long serialVersionUIDDeprecated.- See Also:
-
n
protected final long nDeprecated.The number of keys. -
transform
Deprecated.The transformation strategy to turn objects of typeT
into bit vectors. -
firstFunction
Deprecated.The first function, ornull
. The special output valueescape
denotes thatsecondFunction
should be queried instead. -
secondFunction
Deprecated.The second function. All queries for whichfirstFunction
returnsescape
(or simply all queries, iffirstFunction
isnull
) will be rerouted here. -
remap
protected final long[] remapDeprecated.A mapping from values of the first function to actual values, provided that there is a first function. -
escape
protected final int escapeDeprecated.The escape value returned byfirstFunction
to suggest thatsecondFunction
should be queried instead, provided that there is a first function. -
seed
protected long seedDeprecated.The seed to be used when converting keys to triples. -
width
protected final int widthDeprecated.The width of the output of this function, in bits. -
rankMean
protected final double rankMeanDeprecated.The mean of the rank distribution.
-
-
Constructor Details
-
TwoStepsMWHCFunction
protected TwoStepsMWHCFunction(Iterable<? extends T> keys, TransformationStrategy<? super T> transform, LongBigList values, File tempDir, ChunkedHashStore<T> chunkedHashStore) throws IOException Deprecated.Creates a new two-step function for the given keys and values.- Parameters:
keys
- the keys in the domain of the function.transform
- a transformation strategy for the keys.values
- values to be assigned to each key, in the same order of the iterator returned bykeys
; ifnull
, the assigned value will the ordinal number of each key.tempDir
- a temporary directory for the store files, ornull
for the standard temporary directory.chunkedHashStore
- a chunked hash store containing the keys associated with their rank, ornull
; the store can be unchecked, but in this casekeys
andtransform
must be non-null
.- Throws:
IOException
-
-
Method Details
-
getLong
Deprecated.- Specified by:
getLong
in interfaceObject2LongFunction<T>
-
getLongBySignature
public long getLongBySignature(long[] triple) Deprecated. -
size64
public long size64()Deprecated.- Specified by:
size64
in interfaceSize64
- Overrides:
size64
in classAbstractHashFunction<T>
-
numBits
public long numBits()Deprecated.Returns the number of bits used by this structure.- Returns:
- the number of bits used by this structure.
-
main
Deprecated.
-
TwoStepsGOV3Function
.