Class Builder<T>

Builds a minimal FST (maps an Int32sRef term to an arbitrary output) from pre-sorted terms with outputs. The FST becomes an FSA if you use NoOutputs. The FST is written on-the-fly into a compact serialized format byte array, which can be saved to / loaded from a Directory or used directly for traversal. The FST is always finite (no cycles).

NOTE: The algorithm is described at http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.24.3698

The parameterized type is the output type. See the subclasses of Outputs<T>.

FSTs larger than 2.1GB are now possible (as of Lucene 4.2). FSTs containing more than 2.1B nodes are also now possible, however they cannot be packed.

This is a Lucene.NET EXPERIMENTAL API, use at your own risk

Inheritance

System.Object

Builder

Builder<T>

Namespace: Lucene.Net.Util.Fst

Assembly: Lucene.Net.dll

Syntax

public class Builder<T> : Builder

Type Parameters

Name	Description
T

Constructors

Builder(FST.INPUT_TYPE, Outputs<T>)

Instantiates an FST/FSA builder without any pruning. A shortcut to Builder(FST.INPUT_TYPE, Int32, Int32, Boolean, Boolean, Int32, Outputs<T>, Builder.FreezeTail<T>, Boolean, Single, Boolean, Int32) with pruning options turned off.

Declaration

public Builder(FST.INPUT_TYPE inputType, Outputs<T> outputs)

Parameters

Type	Name	Description
FST.INPUT_TYPE	inputType
Outputs<T>	outputs

Builder(FST.INPUT_TYPE, Int32, Int32, Boolean, Boolean, Int32, Outputs<T>, Builder.FreezeTail<T>, Boolean, Single, Boolean, Int32)

Instantiates an FST/FSA builder with all the possible tuning and construction tweaks. Read parameter documentation carefully.

Declaration

public Builder(FST.INPUT_TYPE inputType, int minSuffixCount1, int minSuffixCount2, bool doShareSuffix, bool doShareNonSingletonNodes, int shareMaxTailLength, Outputs<T> outputs, Builder.FreezeTail<T> freezeTail, bool doPackFST, float acceptableOverheadRatio, bool allowArrayArcs, int bytesPageBits)

Parameters

Type	Name	Description
FST.INPUT_TYPE	inputType	The input type (transition labels). Can be anything from FST.INPUT_TYPE enumeration. Shorter types will consume less memory. Strings (character sequences) are represented as BYTE4 (full unicode codepoints).
System.Int32	minSuffixCount1	If pruning the input graph during construction, this threshold is used for telling if a node is kept or pruned. If transition_count(node) >= minSuffixCount1, the node is kept.
System.Int32	minSuffixCount2	(Note: only Mike McCandless knows what this one is really doing...)
System.Boolean	doShareSuffix	If true, the shared suffixes will be compacted into unique paths. this requires an additional RAM-intensive hash map for lookups in memory. Setting this parameter to false creates a single suffix path for all input sequences. this will result in a larger FST, but requires substantially less memory and CPU during building.
System.Boolean	doShareNonSingletonNodes	Only used if doShareSuffix is true. Set this to true to ensure FST is fully minimal, at cost of more CPU and more RAM during building.
System.Int32	shareMaxTailLength	Only used if doShareSuffix is true. Set this to to ensure FST is fully minimal, at cost of more CPU and more RAM during building.
Outputs<T>	outputs	The output type for each input sequence. Applies only if building an FST. For FSA, use Singleton and NoOutput as the singleton output object.
Builder.FreezeTail<T>	freezeTail
System.Boolean	doPackFST	Pass true to create a packed FST.
System.Single	acceptableOverheadRatio	How to trade speed for space when building the FST. this option is only relevant when doPackFST is true. GetMutable(Int32, Int32, Single)
System.Boolean	allowArrayArcs	Pass false to disable the array arc optimization while building the FST; this will make the resulting FST smaller but slower to traverse.
System.Int32	bytesPageBits	How many bits wide to make each byte[] block in the Lucene.Net.Util.Fst.BytesStore; if you know the FST will be large then make this larger. For example 15 bits = 32768 byte pages.

Properties

MappedStateCount

Declaration

public virtual long MappedStateCount { get; }

Property Value

Type	Description
System.Int64

TermCount

Declaration

public virtual long TermCount { get; }

Property Value

Type	Description
System.Int64

TotStateCount

Declaration

public virtual long TotStateCount { get; }

Property Value

Type	Description
System.Int64

Methods

Add(Int32sRef, T)

It's OK to add the same input twice in a row with different outputs, as long as outputs impls the merge method. Note that input is fully consumed after this method is returned (so caller is free to reuse), but output is not. So if your outputs are changeable (eg ByteSequenceOutputs or Int32SequenceOutputs) then you cannot reuse across calls.

Declaration

public virtual void Add(Int32sRef input, T output)

Parameters

Type	Name	Description
Int32sRef	input
T	output

Finish()

Returns final FST. NOTE: this will return null if nothing is accepted by the FST.

Declaration

public virtual FST<T> Finish()

Returns

Type	Description
FST<T>

GetFstSizeInBytes()

Declaration

public virtual long GetFstSizeInBytes()

Returns

Type	Description
System.Int64