Package elki.index.preprocessed.knn

Class SpacefillingKNNPreprocessor<O extends elki.data.NumberVector>

  • Type Parameters:
    O - Vector type indexed
    All Implemented Interfaces:
    elki.index.Index, elki.index.KNNIndex<O>
    @Reference(authors="Erich Schubert, Arthur Zimek, Hans-Peter Kriegel",
           title="Fast and Scalable Outlier Detection with Approximate Nearest Neighbor Ensembles",
           booktitle="Proc. 20th Int. Conf. Database Systems for Advanced Applications (DASFAA 2015)",
           url="https://doi.org/10.1007/978-3-319-18123-3_2",
           bibkey="DBLP:conf/dasfaa/SchubertZK15")
public class SpacefillingKNNPreprocessor<O extends elki.data.NumberVector>
extends java.lang.Object
implements elki.index.KNNIndex<O>
    Compute the nearest neighbors approximatively using space filling curves.

    This version computes the data projections and stores, then queries this data on-demand. This usually needs less memory (except for very small neighborhood sizes k) than SpacefillingMaterializeKNNPreprocessor, but will also be slower.

    Reference:

    Erich Schubert, Arthur Zimek, Hans-Peter Kriegel
    Fast and Scalable Outlier Detection with Approximate Nearest Neighbor Ensembles
    Proc. 20th Int. Conf. Database Systems for Advanced Applications (DASFAA 2015)

    Since:
    0.7.0
    Author:
    Erich Schubert

    • Field Summary

      Fields 
      Modifier and Type Field Description
      (package private) java.util.List<? extends elki.math.spacefillingcurves.SpatialSorter> curvegen
      Spatial curve generators
      (package private) java.util.List<java.util.List<SpatialPair<elki.database.ids.DBID,​elki.data.NumberVector>>> curves
      Curve storage
      private static elki.logging.Logging LOG
      Class logger
      (package private) elki.math.Mean mean
      Mean number of distance computations
      (package private) int odim
      Number of dimensions to use.
      (package private) elki.database.datastore.WritableDataStore<int[]> positions
      Curve position storage
      (package private) elki.data.projection.random.RandomProjectionFamily proj
      Random projection family to use.
      (package private) java.util.Random random
      Random number generator.
      protected elki.database.relation.Relation<O> relation
      The representation we are bound to.
      (package private) int variants
      Number of variants to generate for each curve
      (package private) double window
      Curve window size

    • Constructor Summary

      Constructors 
      Constructor Description
      SpacefillingKNNPreprocessor​(elki.database.relation.Relation<O> relation, java.util.List<? extends elki.math.spacefillingcurves.SpatialSorter> curvegen, double window, int variants, int odim, elki.data.projection.random.RandomProjectionFamily proj, java.util.Random random)
      Constructor.

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void initialize()  
      elki.database.query.knn.KNNSearcher<elki.database.ids.DBIDRef> kNNByDBID​(elki.database.query.distance.DistanceQuery<O> distanceQuery, int maxk, int flags)  
      elki.database.query.knn.KNNSearcher<O> kNNByObject​(elki.database.query.distance.DistanceQuery<O> distanceQuery, int maxk, int flags)  
      void logStatistics()  
      protected void preprocess()  
      static int[] randomPermutation​(int[] out, java.util.Random random)
      Perform a random permutation of the array, in-place.
      static int[] range​(int start, int end)
      Initialize an integer value range.

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • LOG

        private static final elki.logging.Logging LOG
        Class logger

      • relation

        protected final elki.database.relation.Relation<O extends elki.data.NumberVector> relation
        The representation we are bound to.

      • curvegen

        final java.util.List<? extends elki.math.spacefillingcurves.SpatialSorter> curvegen
        Spatial curve generators

      • window

        final double window
        Curve window size

      • variants

        final int variants
        Number of variants to generate for each curve

      • curves

        java.util.List<java.util.List<SpatialPair<elki.database.ids.DBID,​elki.data.NumberVector>>> curves
        Curve storage

      • positions

        elki.database.datastore.WritableDataStore<int[]> positions
        Curve position storage

      • mean

        elki.math.Mean mean
        Mean number of distance computations

      • odim

        final int odim
        Number of dimensions to use.

      • proj

        elki.data.projection.random.RandomProjectionFamily proj
        Random projection family to use.

      • random

        java.util.Random random
        Random number generator.

    • Constructor Detail

      • SpacefillingKNNPreprocessor

        public SpacefillingKNNPreprocessor​(elki.database.relation.Relation<O> relation,
                                   java.util.List<? extends elki.math.spacefillingcurves.SpatialSorter> curvegen,
                                   double window,
                                   int variants,
                                   int odim,
                                   elki.data.projection.random.RandomProjectionFamily proj,
                                   java.util.Random random)
        Constructor.
        Parameters:
        relation - Relation to index.
        curvegen - Curve generators
        window - Window multiplicator
        variants - Number of curve variants to generate
        odim - Number of dimensions to use -1 == all.
        proj - Random projection to apply
        random - Random number generator

    • Method Detail

      • initialize

        public void initialize()
        Specified by:
        initialize in interface elki.index.Index

      • preprocess

        protected void preprocess()

      • range

        public static int[] range​(int start,
                          int end)
        Initialize an integer value range.
        Parameters:
        start - Starting value
        end - End value (exclusive)
        Returns:
        Array of integers start..end, excluding end.

      • randomPermutation

        public static int[] randomPermutation​(int[] out,
                                      java.util.Random random)
        Perform a random permutation of the array, in-place. Knuth / Fisher-Yates style shuffle
        Parameters:
        out - Prefilled output array.
        random - Random generator.
        Returns:
        Same array.

      • logStatistics

        public void logStatistics()
        Specified by:
        logStatistics in interface elki.index.Index

      • kNNByObject

        public elki.database.query.knn.KNNSearcher<O> kNNByObject​(elki.database.query.distance.DistanceQuery<O> distanceQuery,
                                                          int maxk,
                                                          int flags)
        Specified by:
        kNNByObject in interface elki.index.KNNIndex<O extends elki.data.NumberVector>

      • kNNByDBID

        public elki.database.query.knn.KNNSearcher<elki.database.ids.DBIDRef> kNNByDBID​(elki.database.query.distance.DistanceQuery<O> distanceQuery,
                                                                                int maxk,
                                                                                int flags)
        Specified by:
        kNNByDBID in interface elki.index.KNNIndex<O extends elki.data.NumberVector>