Package org.apache.datasketches.kll

Class KllItemsSketch<T>

java.lang.Object
org.apache.datasketches.kll.KllSketch
org.apache.datasketches.kll.KllItemsSketch<T>
Type Parameters:
T - The sketch data type.
All Implemented Interfaces:
PartitioningFeature<T>, QuantilesAPI, QuantilesGenericAPI<T>, SketchPartitionLimits
public abstract class KllItemsSketch<T> extends KllSketch implements QuantilesGenericAPI<T>
This variation of the KllSketch implements generic data types. The user must provide a suitable implementation of the java.lang.Comparator as well as an implementation of the serializer / deserializer, org.apache.datasketches.common.ArrayOfItemsSerDe.
See Also:

  • Method Details

    • newHeapInstance

      public static <T> KllItemsSketch<T> newHeapInstance(Comparator<? super T> comparator, ArrayOfItemsSerDe<T> serDe)
      Create a new heap instance of this sketch with the default k = 200. The default k = 200 results in a normalized rank error of about 1.65%. Larger K will have smaller error but the sketch will be larger (and slower).
      Type Parameters:
      T - The sketch data type.
      Parameters:
      comparator - to compare items
      serDe - Serializer / deserializer for an array of items, T[].
      Returns:
      new KllItemsSketch on the Java heap.

    • newHeapInstance

      public static <T> KllItemsSketch<T> newHeapInstance(int k, Comparator<? super T> comparator, ArrayOfItemsSerDe<T> serDe)
      Create a new heap instance of this sketch with a given parameter k. k can be between DEFAULT_M and 65535, inclusive. The default k = 200 results in a normalized rank error of about 1.65%. Larger K will have smaller error but the sketch will be larger (and slower).
      Type Parameters:
      T - The sketch data type
      Parameters:
      k - parameter that controls size of the sketch and accuracy of estimates.
      comparator - to compare items
      serDe - Serializer / deserializer for items of type T and T[].
      Returns:
      new KllItemsSketch on the heap.

    • heapify

      public static <T> KllItemsSketch<T> heapify(org.apache.datasketches.memory.Memory srcMem, Comparator<? super T> comparator, ArrayOfItemsSerDe<T> serDe)
      Factory heapify takes a compact sketch image in Memory and instantiates an on-heap sketch. The resulting sketch will not retain any link to the source Memory.
      Type Parameters:
      T - The sketch data type
      Parameters:
      srcMem - a compact Memory image of a sketch serialized by this sketch and of the same type of T.
      comparator - to compare items
      serDe - Serializer / deserializer for items of type T and T[].
      Returns:
      a heap-based sketch based on the given Memory.

    • wrap

      public static <T> KllItemsSketch<T> wrap(org.apache.datasketches.memory.Memory srcMem, Comparator<? super T> comparator, ArrayOfItemsSerDe<T> serDe)
      Constructs a thin wrapper on the heap around a Memory (or WritableMemory) already initialized with a validated sketch image of a type T consistent with the given comparator and serDe. A reference to the Memory is kept in the sketch and must remain in scope consistent with the temporal scope of this sketch. The amount of data kept on the heap is very small. All of the item data originally collected by the given Memory sketch object remains in the Memory object
      Type Parameters:
      T - The sketch data type
      Parameters:
      srcMem - the Memory object that this sketch will wrap.
      comparator - to compare items
      serDe - Serializer / deserializer for items of type T and T[].
      Returns:
      a heap-base sketch that is a thin wrapper around the given srcMem.

    • getCDF

      public double[] getCDF(T[] splitPoints, QuantileSearchCriteria searchCrit)
      Description copied from interface: QuantilesGenericAPI
      Returns an approximation to the Cumulative Distribution Function (CDF) of the input stream as a monotonically increasing array of double ranks (or cumulative probabilities) on the interval [0.0, 1.0], given a set of splitPoints.

      The resulting approximations have a probabilistic guarantee that can be obtained from the getNormalizedRankError(false) function.

      Specified by:
      getCDF in interface QuantilesGenericAPI<T>
      Parameters:
      splitPoints - an array of m unique, monotonically increasing items (of the same type as the input items) that divide the item input domain into m+1 overlapping intervals.

      The start of each interval is below the lowest item retained by the sketch corresponding to a zero rank or zero probability, and the end of the interval is the rank or cumulative probability corresponding to the split point.

      The (m+1)th interval represents 100% of the distribution represented by the sketch and consistent with the definition of a cumulative probability distribution, thus the (m+1)th rank or probability in the returned array is always 1.0.

      If a split point exactly equals a retained item of the sketch and the search criterion is:

      • INCLUSIVE, the resulting cumulative probability will include that item.
      • EXCLUSIVE, the resulting cumulative probability will not include the weight of that split point.

      It is not recommended to include either the minimum or maximum items of the input stream.

      searchCrit - the desired search criteria.
      Returns:
      a discrete CDF array of m+1 double ranks (or cumulative probabilities) on the interval [0.0, 1.0].

    • getClassOfT

      public Class<T> getClassOfT()
      Specified by:
      getClassOfT in interface QuantilesGenericAPI<T>
      Returns:
      the sketch item class

    • getComparator

      public Comparator<? super T> getComparator()
      Description copied from interface: QuantilesGenericAPI
      Returns the Comparator of T
      Specified by:
      getComparator in interface QuantilesGenericAPI<T>
      Returns:
      Comparator of the sketch

    • getPartitionBoundariesFromNumParts

      public GenericPartitionBoundaries<T> getPartitionBoundariesFromNumParts(int numEquallySizedParts, QuantileSearchCriteria searchCrit)
      Description copied from interface: PartitioningFeature
      This method returns an instance of GenericPartitionBoundaries which provides sufficient information for the user to create the given number of equally sized partitions, where "equally sized" refers to an approximately equal number of items per partition.

      The sketch must not be empty.

      Specified by:
      getPartitionBoundariesFromNumParts in interface PartitioningFeature<T>
      Parameters:
      numEquallySizedParts - an integer that specifies the number of equally sized partitions between getMinItem() and getMaxItem(). This must be a positive integer less than getMaxPartitions()
      • A 1 will return: minItem, maxItem.
      • A 2 will return: minItem, median quantile, maxItem.
      • Etc.
      searchCrit - If INCLUSIVE, all the returned quantiles are the upper boundaries of the equally sized partitions with the exception of the lowest returned quantile, which is the lowest boundary of the lowest ranked partition. If EXCLUSIVE, all the returned quantiles are the lower boundaries of the equally sized partitions with the exception of the highest returned quantile, which is the upper boundary of the highest ranked partition.
      Returns:
      an instance of GenericPartitionBoundaries.

    • getPartitionBoundariesFromPartSize

      public GenericPartitionBoundaries<T> getPartitionBoundariesFromPartSize(long nominalPartSizeItems, QuantileSearchCriteria searchCrit)
      Description copied from interface: PartitioningFeature
      This method returns an instance of GenericPartitionBoundaries which provides sufficient information for the user to create the given number of equally sized partitions, where "equally sized" refers to an approximately equal number of items per partition.

      The sketch must not be empty.

      Specified by:
      getPartitionBoundariesFromPartSize in interface PartitioningFeature<T>
      Parameters:
      nominalPartSizeItems - an integer that specifies the nominal size, in items, of each target partition. This must be a positive integer greater than getMinPartitionSizeItems().
      searchCrit - If INCLUSIVE, all the returned quantiles are the upper boundaries of the equally sized partitions with the exception of the lowest returned quantile, which is the lowest boundary of the lowest ranked partition. If EXCLUSIVE, all the returned quantiles are the lower boundaries of the equally sized partitions with the exception of the highest returned quantile, which is the upper boundary of the highest ranked partition.
      Returns:
      an instance of GenericPartitionBoundaries.

    • getPMF

      public double[] getPMF(T[] splitPoints, QuantileSearchCriteria searchCrit)
      Description copied from interface: QuantilesGenericAPI
      Returns an approximation to the Probability Mass Function (PMF) of the input stream as an array of probability masses as doubles on the interval [0.0, 1.0], given a set of splitPoints.

      The resulting approximations have a probabilistic guarantee that can be obtained from the getNormalizedRankError(true) function.

      Specified by:
      getPMF in interface QuantilesGenericAPI<T>
      Parameters:
      splitPoints - an array of m unique, monotonically increasing items (of the same type as the input items) that divide the item input domain into m+1 consecutive, non-overlapping intervals.

      Each interval except for the end intervals starts with a split point and ends with the next split point in sequence.

      The first interval starts below the lowest item retained by the sketch corresponding to a zero rank or zero probability, and ends with the first split point

      The last (m+1)th interval starts with the last split point and ends after the last item retained by the sketch corresponding to a rank or probability of 1.0.

      The sum of the probability masses of all (m+1) intervals is 1.0.

      If the search criterion is:

      • INCLUSIVE, and the upper split point of an interval equals an item retained by the sketch, the interval will include that item. If the lower split point equals an item retained by the sketch, the interval will exclude that item.
      • EXCLUSIVE, and the upper split point of an interval equals an item retained by the sketch, the interval will exclude that item. If the lower split point equals an item retained by the sketch, the interval will include that item.

      It is not recommended to include either the minimum or maximum items of the input stream.

      searchCrit - the desired search criteria.
      Returns:
      a PMF array of m+1 probability masses as doubles on the interval [0.0, 1.0].

    • getQuantile

      public T getQuantile(double rank, QuantileSearchCriteria searchCrit)
      Description copied from interface: QuantilesGenericAPI
      Gets the approximate quantile of the given normalized rank and the given search criterion.
      Specified by:
      getQuantile in interface QuantilesGenericAPI<T>
      Parameters:
      rank - the given normalized rank, a double in the range [0.0, 1.0].
      searchCrit - If INCLUSIVE, the given rank includes all quantiles ≤ the quantile directly corresponding to the given rank. If EXCLUSIVE, he given rank includes all quantiles < the quantile directly corresponding to the given rank.
      Returns:
      the approximate quantile given the normalized rank.
      See Also:

    • getQuantiles

      public T[] getQuantiles(double[] ranks, QuantileSearchCriteria searchCrit)
      Description copied from interface: QuantilesGenericAPI
      Gets an array of quantiles from the given array of normalized ranks.
      Specified by:
      getQuantiles in interface QuantilesGenericAPI<T>
      Parameters:
      ranks - the given array of normalized ranks, each of which must be in the interval [0.0,1.0].
      searchCrit - if INCLUSIVE, the given ranks include all quantiles ≤ the quantile directly corresponding to each rank.
      Returns:
      an array of quantiles corresponding to the given array of normalized ranks.
      See Also:

    • getQuantileLowerBound

      public T getQuantileLowerBound(double rank)
      Description copied from interface: QuantilesGenericAPI
      Gets the lower bound of the quantile confidence interval in which the quantile of the given rank exists.

      Although it is possible to estimate the probability that the true quantile exists within the quantile confidence interval specified by the upper and lower quantile bounds, it is not possible to guarantee the width of the quantile confidence interval as an additive or multiplicative percent of the true quantile.

      Specified by:
      getQuantileLowerBound in interface QuantilesGenericAPI<T>
      Parameters:
      rank - the given normalized rank
      Returns:
      the lower bound of the quantile confidence interval in which the quantile of the given rank exists.

    • getQuantileUpperBound

      public T getQuantileUpperBound(double rank)
      Description copied from interface: QuantilesGenericAPI
      Gets the upper bound of the quantile confidence interval in which the true quantile of the given rank exists.

      Although it is possible to estimate the probability that the true quantile exists within the quantile confidence interval specified by the upper and lower quantile bounds, it is not possible to guarantee the width of the quantile interval as an additive or multiplicative percent of the true quantile.

      Specified by:
      getQuantileUpperBound in interface QuantilesGenericAPI<T>
      Parameters:
      rank - the given normalized rank
      Returns:
      the upper bound of the quantile confidence interval in which the true quantile of the given rank exists.

    • getRank

      public double getRank(T quantile, QuantileSearchCriteria searchCrit)
      Description copied from interface: QuantilesGenericAPI
      Gets the normalized rank corresponding to the given a quantile.
      Specified by:
      getRank in interface QuantilesGenericAPI<T>
      Parameters:
      quantile - the given quantile
      searchCrit - if INCLUSIVE the given quantile is included into the rank.
      Returns:
      the normalized rank corresponding to the given quantile.
      See Also:

    • getRankLowerBound

      public double getRankLowerBound(double rank)
      Gets the lower bound of the rank confidence interval in which the true rank of the given rank exists. The approximate probability that the true rank is within the confidence interval specified by the upper and lower rank bounds for this sketch is 0.99.
      Specified by:
      getRankLowerBound in interface QuantilesAPI
      Parameters:
      rank - the given normalized rank.
      Returns:
      the lower bound of the rank confidence interval in which the true rank of the given rank exists.

    • getRankUpperBound

      public double getRankUpperBound(double rank)
      Gets the upper bound of the rank confidence interval in which the true rank of the given rank exists. The approximate probability that the true rank is within the confidence interval specified by the upper and lower rank bounds for this sketch is 0.99.
      Specified by:
      getRankUpperBound in interface QuantilesAPI
      Parameters:
      rank - the given normalized rank.
      Returns:
      the upper bound of the rank confidence interval in which the true rank of the given rank exists.

    • getRanks

      public double[] getRanks(T[] quantiles, QuantileSearchCriteria searchCrit)
      Description copied from interface: QuantilesGenericAPI
      Gets an array of normalized ranks corresponding to the given array of quantiles and the given search criterion.
      Specified by:
      getRanks in interface QuantilesGenericAPI<T>
      Parameters:
      quantiles - the given array of quantiles
      searchCrit - if INCLUSIVE, the given quantiles include the rank directly corresponding to each quantile.
      Returns:
      an array of normalized ranks corresponding to the given array of quantiles.
      See Also:

    • getSortedView

      public final ItemsSketchSortedView<T> getSortedView()
      Description copied from interface: QuantilesGenericAPI
      Gets the sorted view of this sketch
      Specified by:
      getSortedView in interface QuantilesGenericAPI<T>
      Returns:
      the sorted view of this sketch

    • iterator

      public QuantilesGenericSketchIterator<T> iterator()
      Description copied from interface: QuantilesGenericAPI
      Gets the iterator for this sketch, which is not sorted.
      Specified by:
      iterator in interface QuantilesGenericAPI<T>
      Returns:
      the iterator for this sketch

    • merge

      public final void merge(KllSketch other)
      Description copied from class: KllSketch
      Merges another sketch into this one. Attempting to merge a sketch of the wrong type will throw an exception.
      Specified by:
      merge in class KllSketch
      Parameters:
      other - sketch to merge into this one

    • reset

      public void reset()
      Description copied from interface: QuantilesAPI
      Resets this sketch to the empty state. If the sketch is read only this does nothing.

      The parameter k will not change.

      Specified by:
      reset in interface QuantilesAPI

    • toByteArray

      public byte[] toByteArray()
      Export the current sketch as a compact byte array.
      Returns:
      the current sketch as a compact byte array.

    • toString

      public String toString(boolean withLevels, boolean withLevelsAndItems)
      Description copied from class: KllSketch
      Returns human readable summary information about this sketch. Used for debugging.
      Specified by:
      toString in class KllSketch
      Parameters:
      withLevels - if true includes sketch levels array summary information
      withLevelsAndItems - if true include detail of levels array and items array together
      Returns:
      human readable summary information about this sketch.

    • update

      public void update(T item)
      Description copied from interface: QuantilesGenericAPI
      Updates this sketch with the given item.
      Specified by:
      update in interface QuantilesGenericAPI<T>
      Parameters:
      item - from a stream of items. Nulls are ignored.

    • update

      public void update(T item, long weight)
      Weighted update. Updates this sketch with the given item the number of times specified by the given integer weight.
      Parameters:
      item - the item to be repeated. NaNs are ignored.
      weight - the number of times the update of item is to be repeated. It must be ≥ one.