Packages

trait CMSHasher[K] extends Serializable

The Count-Min sketch uses d (aka depth) pair-wise independent hash functions drawn from a universal hashing family of the form:

h(x) = [a * x + b (mod p)] (mod m)

As a requirement for using CMS you must provide an implicit CMSHasher[K] for the type K of the items you want to count. Algebird ships with several such implicits for commonly used types K such as Long and BigInt.

If your type K is not supported out of the box, you have two options: 1) You provide a "translation" function to convert items of your (unsupported) type K to a supported type such as Double, and then use the contramap function of CMSHasher to create the required CMSHasher[K] for your type (see the documentation of contramap for an example); 2) You implement a CMSHasher[K] from scratch, using the existing CMSHasher implementations as a starting point.

Self Type
CMSHasher[K]
Linear Supertypes
Serializable, AnyRef, Any
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Abstract Value Members

  1. abstract def hash(a: Int, b: Int, width: Int)(x: K): Int

    Returns a * x + b (mod p) (mod width).

Concrete Value Members

  1. final def !=(arg0: Any): Boolean
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  2. final def ##: Int
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  3. final def ==(arg0: Any): Boolean
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  4. final def asInstanceOf[T0]: T0
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  5. def clone(): AnyRef
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    protected[lang]
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    @throws(classOf[java.lang.CloneNotSupportedException]) @native()
  6. def contramap[L](f: (L) => K): CMSHasher[L]

    Given f, a function from L into K, creates a CMSHasher[L] whose hash function is equivalent to:

    Given f, a function from L into K, creates a CMSHasher[L] whose hash function is equivalent to:

    def hash(a: Int, b: Int, width: Int)(x: L): CMSHasher[L] = CMSHasher[K].hash(a, b, width)(f(x))

    Be aware that the use of contramap may come at a cost (e.g. increased time) due to the translation calls between K and L.

    Usage

    The following example creates a CMSHasher for the unsupported type K=Double:

    def f(d: Double): Array[Byte] = {
      val l: Long = java.lang.Double.doubleToLongBits(d)
      java.nio.ByteBuffer.allocate(8).putLong(l).array()
    }
    
    implicit val cmsHasherDouble: CMSHasher[Double] = CMSHasherArrayByte.contramap((d: Double) => f(d))
  7. final def eq(arg0: AnyRef): Boolean
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  8. def equals(arg0: AnyRef): Boolean
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  9. def finalize(): Unit
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  10. final def getClass(): Class[_ <: AnyRef]
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    @native()
  11. def hashCode(): Int
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  12. final def isInstanceOf[T0]: Boolean
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  13. final def ne(arg0: AnyRef): Boolean
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  14. final def notify(): Unit
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    @native()
  15. final def notifyAll(): Unit
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    @native()
  16. def on[L](f: (L) => K): CMSHasher[L]

    Given f, a function from L into K, creates a CMSHasher[L] whose hash function is equivalent to:

    Given f, a function from L into K, creates a CMSHasher[L] whose hash function is equivalent to:

    def hash(a: Int, b: Int, width: Int)(x: L): CMSHasher[L] = CMSHasher[K].hash(a, b, width)(f(x))
  17. final def synchronized[T0](arg0: => T0): T0
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  18. def toString(): String
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  19. final def wait(): Unit
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    @throws(classOf[java.lang.InterruptedException])
  20. final def wait(arg0: Long, arg1: Int): Unit
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    @throws(classOf[java.lang.InterruptedException])
  21. final def wait(arg0: Long): Unit
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    @throws(classOf[java.lang.InterruptedException]) @native()

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