Package org.apache.lucene.util.fst

Class FSTCompiler.Builder<T>

java.lang.Object

org.apache.lucene.util.fst.FSTCompiler.Builder<T>

Enclosing class:

FSTCompiler<T>

public static class FSTCompiler.Builder<T>
extends Object

Fluent-style constructor for FST FSTCompiler.

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

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method	Description
FSTCompiler.Builder<T>	allowFixedLengthArcs(boolean allowFixedLengthArcs)	Pass false to disable the fixed length arc optimization (binary search or direct addressing) while building the FST; this will make the resulting FST smaller but slower to traverse.
FSTCompiler<T>	build()	Creates a new FSTCompiler.
FSTCompiler.Builder<T>	bytesPageBits(int bytesPageBits)	How many bits wide to make each byte[] block in the BytesStore; if you know the FST will be large then make this larger.
FSTCompiler.Builder<T>	directAddressingMaxOversizingFactor(float factor)	Overrides the default the maximum oversizing of fixed array allowed to enable direct addressing of arcs instead of binary search.
FSTCompiler.Builder<T>	minSuffixCount1(int minSuffixCount1)	If pruning the input graph during construction, this threshold is used for telling if a node is kept or pruned.
FSTCompiler.Builder<T>	minSuffixCount2(int minSuffixCount2)	Better pruning: we prune node (and all following nodes) if the prior node has less than this number of terms go through it.
FSTCompiler.Builder<T>	shareMaxTailLength(int shareMaxTailLength)	Only used if shouldShareSuffix is true.
FSTCompiler.Builder<T>	shouldShareNonSingletonNodes(boolean shouldShareNonSingletonNodes)	Only used if shouldShareSuffix is true.
FSTCompiler.Builder<T>	shouldShareSuffix(boolean shouldShareSuffix)	If true, the shared suffixes will be compacted into unique paths.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

Builder

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

Parameters:

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 FST.INPUT_TYPE.BYTE4 (full unicode codepoints).

outputs - The output type for each input sequence. Applies only if building an FST. For FSA, use NoOutputs.getSingleton() and NoOutputs.getNoOutput() as the singleton output object.

Method Details

minSuffixCount1

public FSTCompiler.Builder<T> minSuffixCount1(int 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.

Default = 0.

minSuffixCount2

public FSTCompiler.Builder<T> minSuffixCount2(int minSuffixCount2)

Better pruning: we prune node (and all following nodes) if the prior node has less than this number of terms go through it.

Default = 0.

shouldShareSuffix

public FSTCompiler.Builder<T> shouldShareSuffix(boolean shouldShareSuffix)

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.

Default = true.

shouldShareNonSingletonNodes

public FSTCompiler.Builder<T> shouldShareNonSingletonNodes(boolean shouldShareNonSingletonNodes)

Only used if shouldShareSuffix is true. Set this to true to ensure FST is fully minimal, at cost of more CPU and more RAM during building.

Default = true.

shareMaxTailLength

public FSTCompiler.Builder<T> shareMaxTailLength(int shareMaxTailLength)

Only used if shouldShareSuffix is true. Set this to Integer.MAX_VALUE to ensure FST is fully minimal, at cost of more CPU and more RAM during building.

Default = Integer.MAX_VALUE.

allowFixedLengthArcs

public FSTCompiler.Builder<T> allowFixedLengthArcs(boolean allowFixedLengthArcs)

Pass false to disable the fixed length arc optimization (binary search or direct addressing) while building the FST; this will make the resulting FST smaller but slower to traverse.

Default = true.

bytesPageBits

public FSTCompiler.Builder<T> bytesPageBits(int bytesPageBits)

How many bits wide to make each byte[] block in the BytesStore; if you know the FST will be large then make this larger. For example 15 bits = 32768 byte pages.

Default = 15.

directAddressingMaxOversizingFactor

public FSTCompiler.Builder<T> directAddressingMaxOversizingFactor(float factor)

Overrides the default the maximum oversizing of fixed array allowed to enable direct addressing of arcs instead of binary search.

Setting this factor to a negative value (e.g. -1) effectively disables direct addressing, only binary search nodes will be created.

This factor does not determine whether to encode a node with a list of variable length arcs or with fixed length arcs. It only determines the effective encoding of a node that is already known to be encoded with fixed length arcs.

Default = 1.

build

public FSTCompiler<T> build()

Creates a new FSTCompiler.