Package org.forgerock.bloomfilter

Class BloomFilterStatistics

java.lang.Object
org.forgerock.bloomfilter.BloomFilterStatistics
@Immutable public final class BloomFilterStatistics extends Object
Provides a snapshot of the current statistics and configuration of a Bloom Filter implementation.

  • Constructor Summary

    Constructors
    Constructor
    Description
    BloomFilterStatistics(double configuredFalsePositiveProbability, double expectedFalsePositiveProbability, long capacity, long bitSize, long expiryTime, long estimatedRemainingCapacity)
    Constructs a statistics object with the given parameters.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    equals(Object o)
     
    long
    getBitSize()
    The total memory size of the set, in bits.
    long
    getCapacity()
    The capacity of the set.
    double
    getConfiguredFalsePositiveProbability()
    The configured probability of false positives.
    long
    getEstimatedRemainingCapacity()
    Provides an estimate of the remaining capacity in this bloom filter before it would become saturated.
    double
    getExpectedFalsePositiveProbability()
    The expected probability of false positives given the current state of the set.
    long
    getExpiryTime()
    The time in milliseconds since the UTC epoch until the last element contained in this bloom filter expires.
    int
    hashCode()
     
    boolean
    isSaturated()
    Determines whether the bloom filter expected false positive probability has exceeded the configured false positive probability.
    static long
    optimumBitSize(long capacity, double falsePositiveProbability)
    Calculates the optimum size of a bloom filter (in bits) to achieve the given false positive probability and expected number of insertions (capacity).
    static long
    optimumRemainingCapacity(long bitSize, double expectedFalsePositiveProbability, long capacity)
    Estimates the remaining capacity in an optimum Bloom Filter.
    String
    toString()
     

    Methods inherited from class java.lang.Object

    clone, finalize, getClass, notify, notifyAll, wait, wait, wait

  • Constructor Details

    • BloomFilterStatistics

      public BloomFilterStatistics(double configuredFalsePositiveProbability, double expectedFalsePositiveProbability, long capacity, long bitSize, long expiryTime, long estimatedRemainingCapacity)
      Constructs a statistics object with the given parameters.
      Parameters:
      configuredFalsePositiveProbability - the false positive probability that was configured for this set.
      expectedFalsePositiveProbability - the expected false positive probability given the current state of the set.
      capacity - the expected total number of insertions into the set before it becomes saturated (exceeds the configured false positive probability).
      bitSize - the total memory size of the set in bits.

  • Method Details

    • getConfiguredFalsePositiveProbability

      public double getConfiguredFalsePositiveProbability()
      The configured probability of false positives.
      Returns:
      the false positive probability (FPP) between 0 and 1.

    • getExpectedFalsePositiveProbability

      public double getExpectedFalsePositiveProbability()
      The expected probability of false positives given the current state of the set.
      Returns:
      the expected false positive probability (FPP) between 0 and 1.

    • getCapacity

      public long getCapacity()
      The capacity of the set. This is the expected total number of elements that can be inserted into the set before it exceeds the configured false positive probability.
      Returns:
      the expected capacity of the set.

    • getBitSize

      public long getBitSize()
      The total memory size of the set, in bits. This size is a guide to the memory used for storing the actual elements of the set, and may not reflect fixed-cost overheads such as the size of object headers, configuration options, etc.
      Returns:
      the total memory size of the set in bits.

    • optimumBitSize

      public static long optimumBitSize(long capacity, double falsePositiveProbability)
      Calculates the optimum size of a bloom filter (in bits) to achieve the given false positive probability and expected number of insertions (capacity).
      Parameters:
      capacity - the expected number of insertions into the bloom filter.
      falsePositiveProbability - the desired probability of false positives.
      Returns:
      the optimum number of bits to use for the bloom filter.

    • getEstimatedRemainingCapacity

      public long getEstimatedRemainingCapacity()
      Provides an estimate of the remaining capacity in this bloom filter before it would become saturated.

    • optimumRemainingCapacity

      public static long optimumRemainingCapacity(long bitSize, double expectedFalsePositiveProbability, long capacity)
      Estimates the remaining capacity in an optimum Bloom Filter. This is assuming that the Bloom Filter is close to optimal in space efficiency for the configured false positive probability.
      Parameters:
      bitSize - the size of the Bloom Filter bit-vector in bits.
      expectedFalsePositiveProbability - the expected current false positive probability of the bloom filter.
      capacity - the overall expected capacity of the bloom filter.
      Returns:
      an estimate of the number of elements that could be inserted before the bloom filter becomes saturated.

    • getExpiryTime

      public long getExpiryTime()
      The time in milliseconds since the UTC epoch until the last element contained in this bloom filter expires. This statistic is only relevant to expiring or rolling bloom filter implementations.
      Returns:
      the latest expiry time in milliseconds from the UTC epoch.

    • isSaturated

      public boolean isSaturated()
      Determines whether the bloom filter expected false positive probability has exceeded the configured false positive probability. This happens roughly when half of the bits in the underlying bit vector have been set to 1. No more elements should be inserted into the Bloom Filter beyond this point to avoid exceeding the configured probability of false positives.
      Returns:
      true if the expected false positive probability is greater than the configured probability.

    • equals

      public boolean equals(Object o)
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • toString

      public String toString()
      Overrides:
      toString in class Object