Package org.apache.lucene.index
Enum VectorSimilarityFunction
- All Implemented Interfaces:
Serializable
,Comparable<VectorSimilarityFunction>
Vector similarity function; used in search to return top K most similar vectors to a target
vector. This is a label describing the method used during indexing and searching of the vectors
in order to determine the nearest neighbors.
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Enum Constant Summary
Enum ConstantDescriptionCosine similarity.Dot product.Euclidean distanceMaximum inner product. -
Method Summary
Modifier and TypeMethodDescriptionabstract float
compare
(byte[] v1, byte[] v2) Calculates a similarity score between the two vectors with a specified function.abstract float
compare
(float[] v1, float[] v2) Calculates a similarity score between the two vectors with a specified function.static VectorSimilarityFunction
Returns the enum constant of this type with the specified name.static VectorSimilarityFunction[]
values()
Returns an array containing the constants of this enum type, in the order they are declared.
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Enum Constant Details
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EUCLIDEAN
Euclidean distance -
DOT_PRODUCT
Dot product. NOTE: this similarity is intended as an optimized way to perform cosine similarity. In order to use it, all vectors must be normalized, including both document and query vectors. Using dot product with vectors that are not normalized can result in errors or poor search results. Floating point vectors must be normalized to be of unit length, while byte vectors should simply all have the same norm. -
COSINE
Cosine similarity. NOTE: the preferred way to perform cosine similarity is to normalize all vectors to unit length, and instead useDOT_PRODUCT
. You should only use this function if you need to preserve the original vectors and cannot normalize them in advance. The similarity score is normalised to assure it is positive. -
MAXIMUM_INNER_PRODUCT
Maximum inner product. This is likeDOT_PRODUCT
, but does not require normalization of the inputs. Should be used when the embedding vectors store useful information within the vector magnitude
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Method Details
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values
Returns an array containing the constants of this enum type, in the order they are declared.- Returns:
- an array containing the constants of this enum type, in the order they are declared
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valueOf
Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)- Parameters:
name
- the name of the enum constant to be returned.- Returns:
- the enum constant with the specified name
- Throws:
IllegalArgumentException
- if this enum type has no constant with the specified nameNullPointerException
- if the argument is null
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compare
public abstract float compare(float[] v1, float[] v2) Calculates a similarity score between the two vectors with a specified function. Higher similarity scores correspond to closer vectors.- Parameters:
v1
- a vectorv2
- another vector, of the same dimension- Returns:
- the value of the similarity function applied to the two vectors
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compare
public abstract float compare(byte[] v1, byte[] v2) Calculates a similarity score between the two vectors with a specified function. Higher similarity scores correspond to closer vectors. Each (signed) byte represents a vector dimension.- Parameters:
v1
- a vectorv2
- another vector, of the same dimension- Returns:
- the value of the similarity function applied to the two vectors
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