scala.collection.parallel.immutable.ParHashSet

class ParHashSet[T] extends ParSet[T] with GenericParTemplate[T, ParHashSet] with ParSetLike[T, ParHashSet[T], HashSet[T]] with Serializable

Immutable parallel hash set, based on hash tries.

This is a base trait for Scala parallel collections. It defines behaviour common to all parallel collections. Concrete parallel collections should inherit this trait and ParIterable if they want to define specific combiner factories.

Parallel operations are implemented with divide and conquer style algorithms that parallelize well. The basic idea is to split the collection into smaller parts until they are small enough to be operated on sequentially.

All of the parallel operations are implemented as tasks within this trait. Tasks rely on the concept of splitters, which extend iterators. Every parallel collection defines:

def splitter: IterableSplitter[T]

which returns an instance of IterableSplitter[T] , which is a subtype of Splitter[T] . Splitters have a method remaining to check the remaining number of elements, and method split which is defined by splitters. Method split divides the splitters iterate over into disjunct subsets:

def split: Seq[Splitter]

which splits the splitter into a sequence of disjunct subsplitters. This is typically a very fast operation which simply creates wrappers around the receiver collection. This can be repeated recursively.

Tasks are scheduled for execution through a scala.collection.parallel.TaskSupport object, which can be changed through the tasksupport setter of the collection.

Method newCombiner produces a new combiner. Combiners are an extension of builders. They provide a method combine which combines two combiners and returns a combiner containing elements of both combiners. This method can be implemented by aggressively copying all the elements into the new combiner or by lazily binding their results. It is recommended to avoid copying all of the elements for performance reasons, although that cost might be negligible depending on the use case. Standard parallel collection combiners avoid copying when merging results, relying either on a two-step lazy construction or specific data-structure properties.

Methods:

def seq: Sequential
def par: Repr

produce the sequential or parallel implementation of the collection, respectively. Method par just returns a reference to this parallel collection. Method seq is efficient - it will not copy the elements. Instead, it will create a sequential version of the collection using the same underlying data structure. Note that this is not the case for sequential collections in general - they may copy the elements and produce a different underlying data structure.

The combination of methods toMap , toSeq or toSet along with par and seq is a flexible way to change between different collection types.

Since this trait extends the GenIterable trait, methods like size must also be implemented in concrete collections, while iterator forwards to splitter by default.

Each parallel collection is bound to a specific fork/join pool, on which dormant worker threads are kept. The fork/join pool contains other information such as the parallelism level, that is, the number of processors used. When a collection is created, it is assigned the default fork/join pool found in the scala.parallel package object.

Parallel collections are not necessarily ordered in terms of the foreach operation (see Traversable ). Parallel sequences have a well defined order for iterators - creating an iterator and traversing the elements linearly will always yield the same order. However, bulk operations such as foreach , map or filter always occur in undefined orders for all parallel collections.

Existing parallel collection implementations provide strict parallel iterators. Strict parallel iterators are aware of the number of elements they have yet to traverse. It’s also possible to provide non-strict parallel iterators, which do not know the number of elements remaining. To do this, the new collection implementation must override isStrictSplitterCollection to false . This will make some operations unavailable.

To create a new parallel collection, extend the ParIterable trait, and implement size , splitter , newCombiner and seq . Having an implicit combiner factory requires extending this trait in addition, as well as providing a companion object, as with regular collections.

Method size is implemented as a constant time operation for parallel collections, and parallel collection operations rely on this assumption.

The higher-order functions passed to certain operations may contain side-effects. Since implementations of bulk operations may not be sequential, this means that side-effects may not be predictable and may produce data-races, deadlocks or invalidation of state if care is not taken. It is up to the programmer to either avoid using side-effects or to use some form of synchronization when accessing mutable data.

• T
  • the element type of the set
• Self Type
  • ParHashSet [T]
• Annotations
  • @ SerialVersionUID ()
• Source
  • ParHashSet.scala - Blame
  • ParHashSet.scala - History
• Since
  • 2.9
• See also
  • Scala’s Parallel Collections Library overview section on Parallel Hash Tries for more information.

Type Members

trait Accessor[R, Tp] extends StrictSplitterCheckTask[R, Tp]

Standard accessor task that iterates over the elements of the collection.

• R
  • type of the result of this method ( R for result).
• Tp
  • the representation type of the task at hand.
• Attributes
  • protected
• Definition Classes
  • ParIterableLike

class Aggregate[S] extends Accessor[S, Aggregate[S]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

trait BuilderOps[Elem, To] extends AnyRef

• Definition Classes
  • ParIterableLike

class Collect[S, That] extends Transformer[Combiner[S, That], Collect[S, That]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

abstract class Composite[FR, SR, R, First <: StrictSplitterCheckTask[FR, _], Second <: StrictSplitterCheckTask[SR, _]] extends NonDivisibleTask[R, Composite[FR, SR, R, First, Second]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Copy[U >: T, That] extends Transformer[Combiner[U, That], Copy[U, That]]

• Attributes
  • protected
• Definition Classes
  • ParIterableLike

class CopyToArray[U >: T, This >: Repr] extends Accessor[Unit, CopyToArray[U, This]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Count extends Accessor[Int, Count]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class CreateScanTree[U >: T] extends Transformer[ScanTree[U], CreateScanTree[U]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Drop[U >: T, This >: Repr] extends Transformer[Combiner[U, This], Drop[U, This]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Exists extends Accessor[Boolean, Exists]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Filter[U >: T, This >: Repr] extends Transformer[Combiner[U, This], Filter[U, This]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class FilterNot[U >: T, This >: Repr] extends Transformer[Combiner[U, This], FilterNot[U, This]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Find[U >: T] extends Accessor[Option[U], Find[U]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class FlatMap[S, That] extends Transformer[Combiner[S, That], FlatMap[S, That]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Fold[U >: T] extends Accessor[U, Fold[U]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Forall extends Accessor[Boolean, Forall]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Foreach[S] extends Accessor[Unit, Foreach[S]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class FromScanTree[U >: T, That] extends StrictSplitterCheckTask[Combiner[U, That], FromScanTree[U, That]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class GroupBy[K, U >: T] extends Transformer[HashMapCombiner[K, U], GroupBy[K, U]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Map[S, That] extends Transformer[Combiner[S, That], Map[S, That]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Max[U >: T] extends Accessor[Option[U], Max[U]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Min[U >: T] extends Accessor[Option[U], Min[U]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

trait NonDivisible[R] extends NonDivisibleTask[R, NonDivisible[R]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

trait NonDivisibleTask[R, Tp] extends StrictSplitterCheckTask[R, Tp]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

abstract class ParComposite[FR, SR, R, First <: StrictSplitterCheckTask[FR, _], Second <: StrictSplitterCheckTask[SR, _]] extends Composite[FR, SR, R, First, Second]

Performs two tasks in parallel, and waits for both to finish.

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class ParHashSetIterator extends IterableSplitter[T]

• Source
  • ParHashSet.scala - Blame
  • ParHashSet.scala - History

class Partition[U >: T, This >: Repr] extends Transformer[(Combiner[U, This], Combiner[U, This]), Partition[U, This]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Product[U >: T] extends Accessor[U, Product[U]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Reduce[U >: T] extends Accessor[Option[U], Reduce[U]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

abstract class ResultMapping[R, Tp, R1] extends NonDivisibleTask[R1, ResultMapping[R, Tp, R1]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

type SSCTask[R, Tp] = StrictSplitterCheckTask[R, Tp]

• Definition Classes
  • ParIterableLike

case class ScanLeaf[U >: T](pit: IterableSplitter[U], op: (U, U) ⇒ U, from: Int, len: Int, prev: Option[ScanLeaf[U]], acc: U) extends ScanTree[U] with scala.Product with Serializable

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

case class ScanNode[U >: T](left: ScanTree[U], right: ScanTree[U]) extends ScanTree[U] with scala.Product with Serializable

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

trait ScanTree[U >: T] extends AnyRef

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

abstract class SeqComposite[FR, SR, R, First <: StrictSplitterCheckTask[FR, _], Second <: StrictSplitterCheckTask[SR, _]] extends Composite[FR, SR, R, First, Second]

Sequentially performs one task after another.

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

trait SignallingOps[PI <: DelegatedSignalling] extends AnyRef

• Definition Classes
  • ParIterableLike

class Slice[U >: T, This >: Repr] extends Transformer[Combiner[U, This], Slice[U, This]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Span[U >: T, This >: Repr] extends Transformer[(Combiner[U, This], Combiner[U, This]), Span[U, This]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class SplitAt[U >: T, This >: Repr] extends Transformer[(Combiner[U, This], Combiner[U, This]), SplitAt[U, This]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

trait StrictSplitterCheckTask[R, Tp] extends Task[R, Tp]

• Attributes
  • protected
• Definition Classes
  • ParIterableLike

class Sum[U >: T] extends Accessor[U, Sum[U]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class Take[U >: T, This >: Repr] extends Transformer[Combiner[U, This], Take[U, This]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class TakeWhile[U >: T, This >: Repr] extends Transformer[(Combiner[U, This], Boolean), TakeWhile[U, This]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

trait TaskOps[R, Tp] extends AnyRef

• Definition Classes
  • ParIterableLike

class ToParCollection[U >: T, That] extends Transformer[Combiner[U, That], ToParCollection[U, That]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class ToParMap[K, V, That] extends Transformer[Combiner[(K, V), That], ToParMap[K, V, That]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

trait Transformer[R, Tp] extends Accessor[R, Tp]

• Attributes
  • protected
• Definition Classes
  • ParIterableLike

class Zip[U >: T, S, That] extends Transformer[Combiner[(U, S), That], Zip[U, S, That]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

class ZipAll[U >: T, S, That] extends Transformer[Combiner[(U, S), That], ZipAll[U, S, That]]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

Value Members From scala.Function1

def andThen[A](g: (Boolean) ⇒ A): (T) ⇒ A

Composes two instances of Function1 in a new Function1, with this function applied first.

• A
  • the result type of function g
• g
  • a function R => A
• returns
  • a new function f such that f(x) == g(apply(x))
• Definition Classes
  • Function1
• Annotations
  • @ unspecialized ()

(defined at scala.Function1)

def compose[A](g: (A) ⇒ T): (A) ⇒ Boolean

Composes two instances of Function1 in a new Function1, with this function applied last.

• A
  • the type to which function g can be applied
• g
  • a function A => T1
• returns
  • a new function f such that f(x) == apply(g(x))
• Definition Classes
  • Function1
• Annotations
  • @ unspecialized ()

(defined at scala.Function1)

Value Members From scala.collection.CustomParallelizable

def parCombiner: Combiner[T, ParHashSet[T]]

The default par implementation uses the combiner provided by this method to create a new parallel collection.

• returns
  • a combiner for the parallel collection of type ParRepr
• Attributes
  • protected[this]
• Definition Classes
  • CustomParallelizable → Parallelizable

(defined at scala.collection.CustomParallelizable)

Value Members From scala.collection.GenSetLike

def &(that: GenSet[T]): ParHashSet[T]

Computes the intersection between this set and another set.

Note: Same as intersect .

• that
  • the set to intersect with.
• returns
  • a new set consisting of all elements that are both in this set and in the given set that .
• Definition Classes
  • GenSetLike

(defined at scala.collection.GenSetLike)

def &~(that: GenSet[T]): ParHashSet[T]

The difference of this set and another set.

Note: Same as diff .

• that
  • the set of elements to exclude.
• returns
  • a set containing those elements of this set that are not also contained in the given set that .
• Definition Classes
  • GenSetLike

(defined at scala.collection.GenSetLike)

def apply(elem: T): Boolean

Tests if some element is contained in this set.

This method is equivalent to contains . It allows sets to be interpreted as predicates.

• elem
  • the element to test for membership.
• returns
  • true if elem is contained in this set, false otherwise.
• Definition Classes
  • GenSetLike → Function1

(defined at scala.collection.GenSetLike)

def equals(that: Any): Boolean

Compares this set with another object for equality.

Note: This operation contains an unchecked cast: if that is a set, it will assume with an unchecked cast that it has the same element type as this set. Any subsequent ClassCastException is treated as a false result.

• that
  • the other object
• returns
  • true if that is a set which contains the same elements as this set.
• Definition Classes
  • GenSetLike → Equals → AnyRef → Any

(defined at scala.collection.GenSetLike)

def intersect(that: GenSet[T]): ParHashSet[T]

Computes the intersection between this set and another set.

• that
  • the set to intersect with.
• returns
  • a new set consisting of all elements that are both in this set and in the given set that .
• Definition Classes
  • GenSetLike

(defined at scala.collection.GenSetLike)

def subsetOf(that: GenSet[T]): Boolean

Tests whether this set is a subset of another set.

• that
  • the set to test.
• returns
  • true if this set is a subset of that , i.e. if every element of this set is also an element of that .
• Definition Classes
  • GenSetLike

(defined at scala.collection.GenSetLike)

def |(that: GenSet[T]): ParHashSet[T]

Computes the union between this set and another set.

Note: Same as union .

• that
  • the set to form the union with.
• returns
  • a new set consisting of all elements that are in this set or in the given set that .
• Definition Classes
  • GenSetLike

(defined at scala.collection.GenSetLike)

Value Members From scala.collection.generic.GenericParTemplate

def genericBuilder[B]: Combiner[B, ParHashSet[B]]

The generic builder that builds instances of Traversable at arbitrary element types.

• Definition Classes
  • GenericParTemplate → GenericTraversableTemplate

(defined at scala.collection.generic.GenericParTemplate)

def genericCombiner[B]: Combiner[B, ParHashSet[B]]

• Definition Classes
  • GenericParTemplate

(defined at scala.collection.generic.GenericParTemplate)

def newBuilder: Builder[T, ParHashSet[T]]

The builder that builds instances of type Traversable[A]

• Attributes
  • protected[this]
• Definition Classes
  • GenericParTemplate → GenericTraversableTemplate → HasNewBuilder

(defined at scala.collection.generic.GenericParTemplate)

def newCombiner: Combiner[T, ParHashSet[T]]

• Attributes
  • protected[this]
• Definition Classes
  • GenericParTemplate → HasNewCombiner

(defined at scala.collection.generic.GenericParTemplate)

Value Members From scala.collection.generic.GenericTraversableTemplate

def flatten[B](implicit asTraversable: (T) ⇒ GenTraversableOnce[B]): ParHashSet[B]

[use case]

Converts this immutable parallel hash set of traversable collections into a immutable parallel hash set formed by the elements of these traversable collections.

The resulting collection’s type will be guided by the static type of immutable parallel hash set. For example:

val xs = List(
           Set(1, 2, 3),
           Set(1, 2, 3)
         ).flatten
// xs == List(1, 2, 3, 1, 2, 3)

val ys = Set(
           List(1, 2, 3),
           List(3, 2, 1)
         ).flatten
// ys == Set(1, 2, 3)

• B
  • the type of the elements of each traversable collection.
• returns
  • a new immutable parallel hash set resulting from concatenating all element immutable parallel hash sets.
• Definition Classes
  • GenericTraversableTemplate

(defined at scala.collection.generic.GenericTraversableTemplate)

def transpose[B](implicit asTraversable: (T) ⇒ GenTraversableOnce[B]): ParHashSet[ParHashSet[B]]

Transposes this collection of traversable collections into a collection of collections.

The resulting collection’s type will be guided by the static type of collection. For example:

val xs = List(
           Set(1, 2, 3),
           Set(4, 5, 6)).transpose
// xs == List(
//         List(1, 4),
//         List(2, 5),
//         List(3, 6))

val ys = Vector(
           List(1, 2, 3),
           List(4, 5, 6)).transpose
// ys == Vector(
//         Vector(1, 4),
//         Vector(2, 5),
//         Vector(3, 6))

• B
  • the type of the elements of each traversable collection.
• asTraversable
  • an implicit conversion which asserts that the element type of this collection is a Traversable .
• returns
  • a two-dimensional collection of collections which has as n th row the n th column of this collection.
• Definition Classes
  • GenericTraversableTemplate
• Annotations
  • @migration
• Migration
  • (Changed in version 2.9.0) transpose throws an IllegalArgumentException if collections are not uniformly sized.
• Exceptions thrown
  • IllegalArgumentException if all collections in this collection are not of the same size.

(defined at scala.collection.generic.GenericTraversableTemplate)

def unzip3[A1, A2, A3](implicit asTriple: (T) ⇒ (A1, A2, A3)): (ParHashSet[A1], ParHashSet[A2], ParHashSet[A3])

Converts this collection of triples into three collections of the first, second, and third element of each triple.

val xs = Traversable(
           (1, "one", '1'),
           (2, "two", '2'),
           (3, "three", '3')).unzip3
// xs == (Traversable(1, 2, 3),
//        Traversable(one, two, three),
//        Traversable(1, 2, 3))

• A1
  • the type of the first member of the element triples
• A2
  • the type of the second member of the element triples
• A3
  • the type of the third member of the element triples
• asTriple
  • an implicit conversion which asserts that the element type of this collection is a triple.
• returns
  • a triple of collections, containing the first, second, respectively third member of each element triple of this collection.
• Definition Classes
  • GenericTraversableTemplate

(defined at scala.collection.generic.GenericTraversableTemplate)

def unzip[A1, A2](implicit asPair: (T) ⇒ (A1, A2)): (ParHashSet[A1], ParHashSet[A2])

Converts this collection of pairs into two collections of the first and second half of each pair.

val xs = Traversable(
           (1, "one"),
           (2, "two"),
           (3, "three")).unzip
// xs == (Traversable(1, 2, 3),
//        Traversable(one, two, three))

• A1
  • the type of the first half of the element pairs
• A2
  • the type of the second half of the element pairs
• asPair
  • an implicit conversion which asserts that the element type of this collection is a pair.
• returns
  • a pair of collections, containing the first, respectively second half of each element pair of this collection.
• Definition Classes
  • GenericTraversableTemplate

(defined at scala.collection.generic.GenericTraversableTemplate)

Deprecated Value Members From scala.collection.parallel.ParIterableLike

def view: IterableView[T, HashSet[T]]

• Definition Classes
  • ParIterableLike
• Annotations
  • @ deprecated
• Deprecated
  • (Since version 2.11.0) Use.seq.view instead

(defined at scala.collection.parallel.ParIterableLike)

Value Members From scala.collection.parallel.ParIterableLike

def ++[U >: T, That](that: GenTraversableOnce[U])(implicit bf: CanBuildFrom[ParHashSet[T], U, That]): That

[use case]

Returns a new immutable parallel hash set containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the immutable parallel hash set is the most specific superclass encompassing the element types of the two operands.

Example:

scala> val a = List(1)
a: List[Int] = List(1)

scala> val b = List(2)
b: List[Int] = List(2)

scala> val c = a ++ b
c: List[Int] = List(1, 2)

scala> val d = List('a')
d: List[Char] = List(a)

scala> val e = c ++ d
e: List[AnyVal] = List(1, 2, a)

• B
  • the element type of the returned collection.
• that
  • the traversable to append.
• returns
  • a new immutable parallel hash set which contains all elements of this immutable parallel hash set followed by all elements of that .
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def /:[S](z: S)(op: (S, T) ⇒ S): S

Applies a binary operator to a start value and all elements of this parallel iterable, going left to right.

Note: /: is alternate syntax for foldLeft ; z /: xs is the same as xs foldLeft z .

Examples:

Note that the folding function used to compute b is equivalent to that used to compute c.

scala> val a = List(1,2,3,4)
a: List[Int] = List(1, 2, 3, 4)

scala> val b = (5 /: a)(_+_)
b: Int = 15

scala> val c = (5 /: a)((x,y) => x + y)
c: Int = 15

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.

• z
  • the start value.
• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this parallel iterable, going left to right with the start value z on the left:

    op(...op(op(z, x_1), x_2), ..., x_n)
    

where `x1, ..., xn` are the elements of this parallel iterable.

• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def :\[S](z: S)(op: (T, S) ⇒ S): S

Applies a binary operator to all elements of this parallel iterable and a start value, going right to left.

Note: :\ is alternate syntax for foldRight ; xs :\ z is the same as xs foldRight z .

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.

Examples:

Note that the folding function used to compute b is equivalent to that used to compute c.

scala> val a = List(1,2,3,4)
a: List[Int] = List(1, 2, 3, 4)

scala> val b = (a :\ 5)(_+_)
b: Int = 15

scala> val c = (a :\ 5)((x,y) => x + y)
c: Int = 15

• z
  • the start value
• op
  • the binary operator
• returns
  • the result of inserting op between consecutive elements of this parallel iterable, going right to left with the start value z on the right:

    op(x_1, op(x_2, ... op(x_n, z)...))
    

where `x1, ..., xn` are the elements of this parallel iterable.

• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def aggregate[S](z: ⇒ S)(seqop: (S, T) ⇒ S, combop: (S, S) ⇒ S): S

Aggregates the results of applying an operator to subsequent elements.

This is a more general form of fold and reduce . It has similar semantics, but does not require the result to be a supertype of the element type. It traverses the elements in different partitions sequentially, using seqop to update the result, and then applies combop to results from different partitions. The implementation of this operation may operate on an arbitrary number of collection partitions, so combop may be invoked arbitrary number of times.

For example, one might want to process some elements and then produce a Set . In this case, seqop would process an element and append it to the set, while combop would concatenate two sets from different partitions together. The initial value z would be an empty set.

pc.aggregate(Set[Int]())(_ += process(_), _ ++ _)

Another example is calculating geometric mean from a collection of doubles (one would typically require big doubles for this).

• S
  • the type of accumulated results
• z
  • the initial value for the accumulated result of the partition - this will typically be the neutral element for the seqop operator (e.g. Nil for list concatenation or 0 for summation) and may be evaluated more than once
• seqop
  • an operator used to accumulate results within a partition
• combop
  • an associative operator used to combine results from different partitions
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def bf2seq[S, That](bf: CanBuildFrom[ParHashSet[T], S, That]): CanBuildFrom[HashSet[T], S, That]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

(defined at scala.collection.parallel.ParIterableLike)

implicit def builder2ops[Elem, To](cb: Builder[Elem, To]): BuilderOps[Elem, To]

• Attributes
  • protected
• Definition Classes
  • ParIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def canEqual(other: Any): Boolean

• Definition Classes
  • ParIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def collect[S, That](pf: PartialFunction[T, S])(implicit bf: CanBuildFrom[ParHashSet[T], S, That]): That

[use case]

Builds a new collection by applying a partial function to all elements of this immutable parallel hash set on which the function is defined.

• B
  • the element type of the returned collection.
• pf
  • the partial function which filters and maps the immutable parallel hash set.
• returns
  • a new immutable parallel hash set resulting from applying the given partial function pf to each element on which it is defined and collecting the results. The order of the elements is preserved.
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def combinerFactory: CombinerFactory[T, ParHashSet[T]]

Creates a combiner factory. Each combiner factory instance is used once per invocation of a parallel transformer method for a single collection.

The default combiner factory creates a new combiner every time it is requested, unless the combiner is thread-safe as indicated by its canBeShared method. In this case, the method returns a factory which returns the same combiner each time. This is typically done for concurrent parallel collections, the combiners of which allow thread safe access.

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def combinerFactory[S, That](cbf: () ⇒ Combiner[S, That]): CombinerFactory[S, That]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def copyToArray[U >: T](xs: Array[U]): Unit

[use case]

Copies the elements of this immutable parallel hash set to an array. Fills the given array xs with values of this immutable parallel hash set. Copying will stop once either the end of the current immutable parallel hash set is reached, or the end of the target array is reached.

Note: will not terminate for infinite-sized collections.

• xs
  • the array to fill.
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def copyToArray[U >: T](xs: Array[U], start: Int): Unit

[use case]

Copies the elements of this immutable parallel hash set to an array. Fills the given array xs with values of this immutable parallel hash set, beginning at index start . Copying will stop once either the end of the current immutable parallel hash set is reached, or the end of the target array is reached.

Note: will not terminate for infinite-sized collections.

• xs
  • the array to fill.
• start
  • the starting index.
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def copyToArray[U >: T](xs: Array[U], start: Int, len: Int): Unit

[use case]

Copies the elements of this immutable parallel hash set to an array. Fills the given array xs with at most len elements of this immutable parallel hash set, starting at position start . Copying will stop once either the end of the current immutable parallel hash set is reached, or the end of the target array is reached, or len elements have been copied.

Note: will not terminate for infinite-sized collections.

• xs
  • the array to fill.
• start
  • the starting index.
• len
  • the maximal number of elements to copy.
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def count(p: (T) ⇒ Boolean): Int

Counts the number of elements in the parallel iterable which satisfy a predicate.

• p
  • the predicate used to test elements.
• returns
  • the number of elements satisfying the predicate p .
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def debugBuffer: ArrayBuffer[String]

• Definition Classes
  • ParIterableLike

(defined at scala.collection.parallel.ParIterableLike)

implicit def delegatedSignalling2ops[PI <: DelegatedSignalling](it: PI): SignallingOps[PI]

• Attributes
  • protected
• Definition Classes
  • ParIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def drop(n: Int): ParHashSet[T]

Selects all elements except first n ones.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• n
  • the number of elements to drop from this parallel iterable.
• returns
  • a parallel iterable consisting of all elements of this parallel iterable except the first n ones, or else the empty parallel iterable, if this parallel iterable has less than n elements.
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def dropWhile(pred: (T) ⇒ Boolean): ParHashSet[T]

Drops all elements in the longest prefix of elements that satisfy the predicate, and returns a collection composed of the remaining elements.

This method will use indexFlag signalling capabilities. This means that splitters may set and read the indexFlag state. The index flag is initially set to maximum integer value.

• pred
  • the predicate used to test the elements
• returns
  • a collection composed of all the elements after the longest prefix of elements in this parallel iterable that satisfy the predicate pred
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def exists(p: (T) ⇒ Boolean): Boolean

Tests whether a predicate holds for some element of this parallel iterable.

This method will use abort signalling capabilities. This means that splitters may send and read abort signals.

• p
  • a predicate used to test elements
• returns
  • true if p holds for some element, false otherwise
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def filter(pred: (T) ⇒ Boolean): ParHashSet[T]

Selects all elements of this parallel iterable which satisfy a predicate.

• pred
  • the predicate used to test elements.
• returns
  • a new parallel iterable consisting of all elements of this parallel iterable that satisfy the given predicate p . Their order may not be preserved.
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def filterNot(pred: (T) ⇒ Boolean): ParHashSet[T]

Selects all elements of this parallel iterable which do not satisfy a predicate.

• pred
  • the predicate used to test elements.
• returns
  • a new parallel iterable consisting of all elements of this parallel iterable that do not satisfy the given predicate p . Their order may not be preserved.
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def find(p: (T) ⇒ Boolean): Option[T]

Finds some element in the collection for which the predicate holds, if such an element exists. The element may not necessarily be the first such element in the iteration order.

If there are multiple elements obeying the predicate, the choice is nondeterministic.

This method will use abort signalling capabilities. This means that splitters may send and read abort signals.

• p
  • predicate used to test the elements
• returns
  • an option value with the element if such an element exists, or None otherwise
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def flatMap[S, That](f: (T) ⇒ GenTraversableOnce[S])(implicit bf: CanBuildFrom[ParHashSet[T], S, That]): That

[use case]

Builds a new collection by applying a function to all elements of this immutable parallel hash set and using the elements of the resulting collections.

For example:

def getWords(lines: Seq[String]): Seq[String] = lines flatMap (line => line split "\\W+")

The type of the resulting collection is guided by the static type of immutable parallel hash set. This might cause unexpected results sometimes. For example:

// lettersOf will return a Seq[Char] of likely repeated letters, instead of a Set
def lettersOf(words: Seq[String]) = words flatMap (word => word.toSet)

// lettersOf will return a Set[Char], not a Seq
def lettersOf(words: Seq[String]) = words.toSet flatMap (word => word.toSeq)

// xs will be an Iterable[Int]
val xs = Map("a" -> List(11,111), "b" -> List(22,222)).flatMap(_._2)

// ys will be a Map[Int, Int]
val ys = Map("a" -> List(1 -> 11,1 -> 111), "b" -> List(2 -> 22,2 -> 222)).flatMap(_._2)

• B
  • the element type of the returned collection.
• f
  • the function to apply to each element.
• returns
  • a new immutable parallel hash set resulting from applying the given collection-valued function f to each element of this immutable parallel hash set and concatenating the results.
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def foldLeft[S](z: S)(op: (S, T) ⇒ S): S

Applies a binary operator to a start value and all elements of this parallel iterable, going left to right.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.

• z
  • the start value.
• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this parallel iterable, going left to right with the start value z on the left:

    op(...op(z, x_1), x_2, ..., x_n)
    

where `x1, ..., xn` are the elements of this parallel iterable. Returns `z`
if this parallel iterable is empty.

• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def foldRight[S](z: S)(op: (T, S) ⇒ S): S

Applies a binary operator to all elements of this parallel iterable and a start value, going right to left.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.

• z
  • the start value.
• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this parallel iterable, going right to left with the start value z on the right:

    op(x_1, op(x_2, ... op(x_n, z)...))
    

where `x1, ..., xn` are the elements of this parallel iterable. Returns `z`
if this parallel iterable is empty.

• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def fold[U >: T](z: U)(op: (U, U) ⇒ U): U

Folds the elements of this sequence using the specified associative binary operator. The order in which the elements are reduced is unspecified and may be nondeterministic.

Note this method has a different signature than the foldLeft and foldRight methods of the trait Traversable . The result of folding may only be a supertype of this parallel collection’s type parameter T .

• U
  • a type parameter for the binary operator, a supertype of T .
• z
  • a neutral element for the fold operation, it may be added to the result an arbitrary number of times, not changing the result (e.g. Nil for list concatenation, 0 for addition, or 1 for multiplication)
• op
  • a binary operator that must be associative
• returns
  • the result of applying fold operator op between all the elements and z
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def forall(p: (T) ⇒ Boolean): Boolean

Tests whether a predicate holds for all elements of this parallel iterable.

This method will use abort signalling capabilities. This means that splitters may send and read abort signals.

• p
  • a predicate used to test elements
• returns
  • true if p holds for all elements, false otherwise
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def foreach[U](f: (T) ⇒ U): Unit

Applies a function f to all the elements of parallel iterable in an undefined order.

• U
  • the result type of the function applied to each element, which is always discarded
• f
  • function applied to each element
• Definition Classes
  • ParIterableLike → GenTraversableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def groupBy[K](f: (T) ⇒ K): ParMap[K, ParHashSet[T]]

Partitions this parallel iterable into a map of parallel iterables according to some discriminator function.

Note: this method is not re-implemented by views. This means when applied to a view it will always force the view and return a new parallel iterable.

• K
  • the type of keys returned by the discriminator function.
• f
  • the discriminator function.
• returns
  • A map from keys to parallel iterables such that the following invariant holds:

    (xs groupBy f)(k) = xs filter (x => f(x) == k)
    

That is, every key `k` is bound to a parallel iterable of those elements
 `x` for which `f(x)` equals `k` .

• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def init: ParHashSet[T]

Selects all elements except the last.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• returns
  • a parallel iterable consisting of all elements of this parallel iterable except the last one.
• Definition Classes
  • ParIterableLike → GenTraversableLike
• Exceptions thrown
  • UnsupportedOperationException if the parallel iterable is empty.

(defined at scala.collection.parallel.ParIterableLike)

def iterator: Splitter[T]

Creates a new split iterator used to traverse the elements of this collection.

By default, this method is implemented in terms of the protected splitter method.

• returns
  • a split iterator
• Definition Classes
  • ParIterableLike → GenIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def map[S, That](f: (T) ⇒ S)(implicit bf: CanBuildFrom[ParHashSet[T], S, That]): That

[use case]

Builds a new collection by applying a function to all elements of this immutable parallel hash set.

• B
  • the element type of the returned collection.
• f
  • the function to apply to each element.
• returns
  • a new immutable parallel hash set resulting from applying the given function f to each element of this immutable parallel hash set and collecting the results.
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def maxBy[S](f: (T) ⇒ S)(implicit cmp: Ordering[S]): T

[use case]

Finds the first element which yields the largest value measured by function f.

• B
  • The result type of the function f.
• f
  • The measuring function.
• returns
  • the first element of this immutable parallel hash set with the largest value measured by function f.
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def minBy[S](f: (T) ⇒ S)(implicit cmp: Ordering[S]): T

[use case]

Finds the first element which yields the smallest value measured by function f.

• B
  • The result type of the function f.
• f
  • The measuring function.
• returns
  • the first element of this immutable parallel hash set with the smallest value measured by function f.
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def mkString(sep: String): String

Displays all elements of this parallel iterable in a string using a separator string.

• sep
  • the separator string.
• returns
  • a string representation of this parallel iterable. In the resulting string the string representations (w.r.t. the method toString ) of all elements of this parallel iterable are separated by the string sep .
• Definition Classes
  • ParIterableLike → GenTraversableOnce

Example:

List(1, 2, 3).mkString("|") = "1|2|3"

(defined at scala.collection.parallel.ParIterableLike)

def mkString(start: String, sep: String, end: String): String

Displays all elements of this parallel iterable in a string using start, end, and separator strings.

• start
  • the starting string.
• sep
  • the separator string.
• end
  • the ending string.
• returns
  • a string representation of this parallel iterable. The resulting string begins with the string start and ends with the string end . Inside, the string representations (w.r.t. the method toString ) of all elements of this parallel iterable are separated by the string sep .
• Definition Classes
  • ParIterableLike → GenTraversableOnce

Example:

List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"

(defined at scala.collection.parallel.ParIterableLike)

def par: ParHashSet[T]

Returns a parallel implementation of this collection.

For most collection types, this method creates a new parallel collection by copying all the elements. For these collection, par takes linear time. Mutable collections in this category do not produce a mutable parallel collection that has the same underlying dataset, so changes in one collection will not be reflected in the other one.

Specific collections (e.g. ParArray or mutable.ParHashMap ) override this default behaviour by creating a parallel collection which shares the same underlying dataset. For these collections, par takes constant or sublinear time.

All parallel collections return a reference to themselves.

• returns
  • a parallel implementation of this collection
• Definition Classes
  • ParIterableLike → CustomParallelizable → Parallelizable

(defined at scala.collection.parallel.ParIterableLike)

def partition(pred: (T) ⇒ Boolean): (ParHashSet[T], ParHashSet[T])

Partitions this parallel iterable in two parallel iterables according to a predicate.

• pred
  • the predicate on which to partition.
• returns
  • a pair of parallel iterables: the first parallel iterable consists of all elements that satisfy the predicate p and the second parallel iterable consists of all elements that don’t. The relative order of the elements in the resulting parallel iterables may not be preserved.
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def reduceLeftOption[U >: T](op: (U, T) ⇒ U): Option[U]

Optionally applies a binary operator to all elements of this parallel iterable, going left to right.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.

• op
  • the binary operator.
• returns
  • an option value containing the result of reduceLeft(op) if this parallel iterable is nonempty, None otherwise.
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def reduceLeft[U >: T](op: (U, T) ⇒ U): U

• Definition Classes
  • ParIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def reduceOption[U >: T](op: (U, U) ⇒ U): Option[U]

Optionally reduces the elements of this sequence using the specified associative binary operator.

The order in which operations are performed on elements is unspecified and may be nondeterministic.

Note this method has a different signature than the reduceLeftOption and reduceRightOption methods of the trait Traversable . The result of reducing may only be a supertype of this parallel collection’s type parameter T .

• U
  • A type parameter for the binary operator, a supertype of T .
• op
  • A binary operator that must be associative.
• returns
  • An option value containing result of applying reduce operator op between all the elements if the collection is nonempty, and None otherwise.
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def reduceRightOption[U >: T](op: (T, U) ⇒ U): Option[U]

Optionally applies a binary operator to all elements of this parallel iterable, going right to left.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.

• op
  • the binary operator.
• returns
  • an option value containing the result of reduceRight(op) if this parallel iterable is nonempty, None otherwise.
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def reduceRight[U >: T](op: (T, U) ⇒ U): U

Applies a binary operator to all elements of this parallel iterable, going right to left.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered. or the operator is associative and commutative.

• op
  • the binary operator.
• returns
  • the result of inserting op between consecutive elements of this parallel iterable, going right to left:

    op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...))
    

where `x1, ..., xn` are the elements of this parallel iterable.

• Definition Classes
  • ParIterableLike → GenTraversableOnce
• Exceptions thrown
  • UnsupportedOperationException if this parallel iterable is empty.

(defined at scala.collection.parallel.ParIterableLike)

def reduce[U >: T](op: (U, U) ⇒ U): U

Reduces the elements of this sequence using the specified associative binary operator.

The order in which operations are performed on elements is unspecified and may be nondeterministic.

Note this method has a different signature than the reduceLeft and reduceRight methods of the trait Traversable . The result of reducing may only be a supertype of this parallel collection’s type parameter T .

• U
  • A type parameter for the binary operator, a supertype of T .
• op
  • A binary operator that must be associative.
• returns
  • The result of applying reduce operator op between all the elements if the collection is nonempty.
• Definition Classes
  • ParIterableLike → GenTraversableOnce
• Exceptions thrown
  • UnsupportedOperationException if this parallel iterable is empty.

(defined at scala.collection.parallel.ParIterableLike)

def repr: ParHashSet[T]

• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def sameElements[U >: T](that: GenIterable[U]): Boolean

[use case]

Checks if the other iterable collection contains the same elements in the same order as this immutable parallel hash set.

Note: might return different results for different runs, unless the underlying collection type is ordered.

Note: will not terminate for infinite-sized collections.

• that
  • the collection to compare with.
• returns
  • true , if both collections contain the same elements in the same order, false otherwise.
• Definition Classes
  • ParIterableLike → GenIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def scan[U >: T, That](z: U)(op: (U, U) ⇒ U)(implicit bf: CanBuildFrom[ParHashSet[T], U, That]): That

[use case]

Computes a prefix scan of the elements of the collection.

Note: The neutral element z may be applied more than once.

• z
  • neutral element for the operator op
• op
  • the associative operator for the scan
• returns
  • a new immutable parallel hash set containing the prefix scan of the elements in this immutable parallel hash set
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def scanLeft[S, That](z: S)(op: (S, T) ⇒ S)(implicit bf: CanBuildFrom[ParHashSet[T], S, That]): That

Produces a collection containing cumulative results of applying the operator going left to right.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• That
  • the actual type of the resulting collection
• z
  • the initial value
• op
  • the binary operator applied to the intermediate result and the element
• bf
  • an implicit value of class CanBuildFrom which determines the result class That from the current representation type Repr and and the new element type B .
• returns
  • collection with intermediate results
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def scanRight[S, That](z: S)(op: (T, S) ⇒ S)(implicit bf: CanBuildFrom[ParHashSet[T], S, That]): That

Produces a collection containing cumulative results of applying the operator going right to left. The head of the collection is the last cumulative result.

Note: will not terminate for infinite-sized collections.

Note: might return different results for different runs, unless the underlying collection type is ordered.

Example:

List(1, 2, 3, 4).scanRight(0)(_ + _) == List(10, 9, 7, 4, 0)

• That
  • the actual type of the resulting collection
• z
  • the initial value
• op
  • the binary operator applied to the intermediate result and the element
• bf
  • an implicit value of class CanBuildFrom which determines the result class That from the current representation type Repr and and the new element type B .
• returns
  • collection with intermediate results
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def sequentially[S, That <: Parallel](b: (HashSet[T]) ⇒ Parallelizable[S, That]): ParHashSet[T]

• Attributes
  • protected[this]
• Definition Classes
  • ParIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def slice(unc_from: Int, unc_until: Int): ParHashSet[T]

Selects an interval of elements. The returned collection is made up of all elements x which satisfy the invariant:

from <= indexOf(x) < until

Note: might return different results for different runs, unless the underlying collection type is ordered.

• unc_from
  • the lowest index to include from this parallel iterable.
• unc_until
  • the lowest index to EXCLUDE from this parallel iterable.
• returns
  • a parallel iterable containing the elements greater than or equal to index from extending up to (but not including) index until of this parallel iterable.
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def span(pred: (T) ⇒ Boolean): (ParHashSet[T], ParHashSet[T])

Splits this parallel iterable into a prefix/suffix pair according to a predicate.

This method will use indexFlag signalling capabilities. This means that splitters may set and read the indexFlag state. The index flag is initially set to maximum integer value.

• pred
  • the predicate used to test the elements
• returns
  • a pair consisting of the longest prefix of the collection for which all the elements satisfy pred , and the rest of the collection
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def splitAt(n: Int): (ParHashSet[T], ParHashSet[T])

Splits this parallel iterable into two at a given position. Note: c splitAt n is equivalent to (but possibly more efficient than) (c take n, c drop n) .

Note: might return different results for different runs, unless the underlying collection type is ordered.

• n
  • the position at which to split.
• returns
  • a pair of parallel iterables consisting of the first n elements of this parallel iterable, and the other elements.
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def tail: ParHashSet[T]

Selects all elements except the first.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• returns
  • a parallel iterable consisting of all elements of this parallel iterable except the first one.
• Definition Classes
  • ParIterableLike → GenTraversableLike
• Exceptions thrown
  • UnsupportedOperationException if the parallel iterable is empty.

(defined at scala.collection.parallel.ParIterableLike)

def take(n: Int): ParHashSet[T]

Selects first n elements.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• n
  • the number of elements to take from this parallel iterable.
• returns
  • a parallel iterable consisting only of the first n elements of this parallel iterable, or else the whole parallel iterable, if it has less than n elements.
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

def takeWhile(pred: (T) ⇒ Boolean): ParHashSet[T]

Takes the longest prefix of elements that satisfy the predicate.

This method will use indexFlag signalling capabilities. This means that splitters may set and read the indexFlag state. The index flag is initially set to maximum integer value.

• pred
  • the predicate used to test the elements
• returns
  • the longest prefix of this parallel iterable of elements that satisfy the predicate pred
• Definition Classes
  • ParIterableLike → GenTraversableLike

(defined at scala.collection.parallel.ParIterableLike)

implicit def task2ops[R, Tp](tsk: SSCTask[R, Tp]): TaskOps[R, Tp]

• Attributes
  • protected
• Definition Classes
  • ParIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def tasksupport: TaskSupport

The task support object which is responsible for scheduling and load-balancing tasks to processors.

• Definition Classes
  • ParIterableLike
• See also
  • scala.collection.parallel.TaskSupport

(defined at scala.collection.parallel.ParIterableLike)

def tasksupport_=(ts: TaskSupport): Unit

Changes the task support object which is responsible for scheduling and load-balancing tasks to processors.

A task support object can be changed in a parallel collection after it has been created, but only during a quiescent period, i.e. while there are no concurrent invocations to parallel collection methods.

Here is a way to change the task support of a parallel collection:

import scala.collection.parallel._
val pc = mutable.ParArray(1, 2, 3)
pc.tasksupport = new ForkJoinTaskSupport(
  new java.util.concurrent.ForkJoinPool(2))

• Definition Classes
  • ParIterableLike
• See also
  • scala.collection.parallel.TaskSupport

(defined at scala.collection.parallel.ParIterableLike)

def toBuffer[U >: T]: Buffer[U]

Uses the contents of this parallel iterable to create a new mutable buffer.

Note: will not terminate for infinite-sized collections.

• returns
  • a buffer containing all elements of this parallel iterable.
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def toIndexedSeq: immutable.IndexedSeq[T]

Converts this parallel iterable to an indexed sequence.

Note: will not terminate for infinite-sized collections.

• returns
  • an indexed sequence containing all elements of this parallel iterable.
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def toIterator: scala.Iterator[T]

Returns an Iterator over the elements in this parallel iterable. Will return the same Iterator if this instance is already an Iterator.

Note: will not terminate for infinite-sized collections.

• returns
  • an Iterator containing all elements of this parallel iterable.
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def toMap[K, V](implicit ev: <:<[T, (K, V)]): ParMap[K, V]

[use case]

Converts this immutable parallel hash set to a map. This method is unavailable unless the elements are members of Tuple2, each ((T, U)) becoming a key-value pair in the map. Duplicate keys will be overwritten by later keys: if this is an unordered collection, which key is in the resulting map is undefined.

Note: will not terminate for infinite-sized collections.

• returns
  • a map of type immutable.Map[T, U] containing all key/value pairs of type (T, U) of this immutable parallel hash set.
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def toParCollection[U >: T, That](cbf: () ⇒ Combiner[U, That]): That

• Attributes
  • protected
• Definition Classes
  • ParIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def toParMap[K, V, That](cbf: () ⇒ Combiner[(K, V), That])(implicit ev: <:<[T, (K, V)]): That

• Attributes
  • protected
• Definition Classes
  • ParIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def toTraversable: GenTraversable[T]

Converts this parallel iterable to an unspecified Traversable. Will return the same collection if this instance is already Traversable.

Note: will not terminate for infinite-sized collections.

• returns
  • a Traversable containing all elements of this parallel iterable.
• Definition Classes
  • ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.ParIterableLike)

def withFilter(pred: (T) ⇒ Boolean): ParHashSet[T]

• Definition Classes
  • ParIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def wrap[R](body: ⇒ R): NonDivisible[R]

• Attributes
  • protected
• Definition Classes
  • ParIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def zipAll[S, U >: T, That](that: GenIterable[S], thisElem: U, thatElem: S)(implicit bf: CanBuildFrom[ParHashSet[T], (U, S), That]): That

[use case]

Returns a immutable parallel hash set formed from this immutable parallel hash set and another iterable collection by combining corresponding elements in pairs. If one of the two collections is shorter than the other, placeholder elements are used to extend the shorter collection to the length of the longer.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• B
  • the type of the second half of the returned pairs
• that
  • The iterable providing the second half of each result pair
• thisElem
  • the element to be used to fill up the result if this immutable parallel hash set is shorter than that .
• thatElem
  • the element to be used to fill up the result if that is shorter than this immutable parallel hash set.
• returns
  • a new immutable parallel hash set containing pairs consisting of corresponding elements of this immutable parallel hash set and that . The length of the returned collection is the maximum of the lengths of this immutable parallel hash set and that . If this immutable parallel hash set is shorter than that , thisElem values are used to pad the result. If that is shorter than this immutable parallel hash set, thatElem values are used to pad the result.
• Definition Classes
  • ParIterableLike → GenIterableLike

(defined at scala.collection.parallel.ParIterableLike)

def zipWithIndex[U >: T, That](implicit bf: CanBuildFrom[ParHashSet[T], (U, Int), That]): That

[use case]

Zips this immutable parallel hash set with its indices.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• returns
  • A new immutable parallel hash set containing pairs consisting of all elements of this immutable parallel hash set paired with their index. Indices start at 0 .
• Definition Classes
  • ParIterableLike → GenIterableLike

Example:

List("a", "b", "c").zipWithIndex = List(("a", 0), ("b", 1), ("c", 2))

(defined at scala.collection.parallel.ParIterableLike)

def zip[U >: T, S, That](that: GenIterable[S])(implicit bf: CanBuildFrom[ParHashSet[T], (U, S), That]): That

[use case]

Returns a immutable parallel hash set formed from this immutable parallel hash set and another iterable collection by combining corresponding elements in pairs. If one of the two collections is longer than the other, its remaining elements are ignored.

Note: might return different results for different runs, unless the underlying collection type is ordered.

• B
  • the type of the second half of the returned pairs
• that
  • The iterable providing the second half of each result pair
• returns
  • a new immutable parallel hash set containing pairs consisting of corresponding elements of this immutable parallel hash set and that . The length of the returned collection is the minimum of the lengths of this immutable parallel hash set and that .
• Definition Classes
  • ParIterableLike → GenIterableLike

(defined at scala.collection.parallel.ParIterableLike)

Value Members From scala.collection.parallel.ParSetLike

def diff(that: GenSet[T]): ParHashSet[T]

Computes the difference of this set and another set.

• that
  • the set of elements to exclude.
• returns
  • a set containing those elements of this set that are not also contained in the given set that .
• Definition Classes
  • ParSetLike → GenSetLike

(defined at scala.collection.parallel.ParSetLike)

def union(that: GenSet[T]): ParHashSet[T]

Computes the union between of set and another set.

• that
  • the set to form the union with.
• returns
  • a new set consisting of all elements that are in this set or in the given set that .
• Definition Classes
  • ParSetLike → GenSetLike

(defined at scala.collection.parallel.ParSetLike)

Instance Constructors From scala.collection.parallel.immutable.ParHashSet

new ParHashSet()

(defined at scala.collection.parallel.immutable.ParHashSet)

Value Members From scala.collection.parallel.immutable.ParHashSet

def +(e: T): ParHashSet[T]

• Definition Classes
  • ParHashSet → GenSetLike

(defined at scala.collection.parallel.immutable.ParHashSet)

def -(e: T): ParHashSet[T]

• Definition Classes
  • ParHashSet → GenSetLike

(defined at scala.collection.parallel.immutable.ParHashSet)

def companion: GenericCompanion[ParHashSet] with GenericParCompanion[ParHashSet]

The factory companion object that builds instances of class immutable.ParHashSet . (or its Iterable superclass where class immutable.ParHashSet is not a Seq .)

• Definition Classes
  • ParHashSet → ParSet → ParIterable → ParSet → ParIterable → GenericParTemplate → GenSet → GenIterable → GenTraversable → GenericTraversableTemplate

(defined at scala.collection.parallel.immutable.ParHashSet)

def contains(e: T): Boolean

• Definition Classes
  • ParHashSet → GenSetLike

(defined at scala.collection.parallel.immutable.ParHashSet)

def empty: ParHashSet[T]

• Definition Classes
  • ParHashSet → ParSet → ParSet → ParSetLike → GenericSetTemplate

(defined at scala.collection.parallel.immutable.ParHashSet)

def reuse[S, That](oldc: Option[Combiner[S, That]], newc: Combiner[S, That]): Combiner[S, That]

Optionally reuses an existing combiner for better performance. By default it doesn’t - subclasses may override this behaviour. The provided combiner oldc that can potentially be reused will be either some combiner from the previous computational task, or None if there was no previous phase (in which case this method must return newc ).

• oldc
  • The combiner that is the result of the previous task, or None if there was no previous task.
• newc
  • The new, empty combiner that can be used.
• returns
  • Either newc or oldc .
• Attributes
  • protected
• Definition Classes
  • ParHashSet → ParIterableLike

(defined at scala.collection.parallel.immutable.ParHashSet)

def seq: HashSet[T]

• Definition Classes
  • ParHashSet → ParIterableLike → GenSet → GenIterable → GenTraversable → GenSetLike → Parallelizable → GenTraversableOnce

(defined at scala.collection.parallel.immutable.ParHashSet)

def splitter: IterableSplitter[T]

Creates a new parallel iterator used to traverse the elements of this parallel collection. This iterator is more specific than the iterator of the returned by iterator , and augmented with additional accessor and transformer methods.

• returns
  • a parallel iterator
• Definition Classes
  • ParHashSet → ParIterableLike

(defined at scala.collection.parallel.immutable.ParHashSet)

Value Members From scala.collection.parallel.immutable.ParIterable

def toIterable: ParIterable[T]

Converts this parallel iterable to an iterable collection. Note that the choice of target Iterable is lazy in this default implementation as this TraversableOnce may be lazy and unevaluated (i.e. it may be an iterator which is only traversable once).

Note: will not terminate for infinite-sized collections.

• returns
  • an Iterable containing all elements of this parallel iterable.
• Definition Classes
  • ParIterable → ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.immutable.ParIterable)

def toSeq: ParSeq[T]

Converts this parallel iterable to a sequence. As with toIterable , it’s lazy in this default implementation, as this TraversableOnce may be lazy and unevaluated.

Note: will not terminate for infinite-sized collections.

• returns
  • a sequence containing all elements of this parallel iterable.
• Definition Classes
  • ParIterable → ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.immutable.ParIterable)

Value Members From scala.collection.parallel.immutable.ParSet

def toSet[U >: T]: ParSet[U]

Converts this mutable parallel set to a set.

Note: will not terminate for infinite-sized collections.

• returns
  • a set containing all elements of this mutable parallel set.
• Definition Classes
  • ParSet → ParIterableLike → GenTraversableOnce

(defined at scala.collection.parallel.immutable.ParSet)

Value Members From Implicit scala.collection.parallel.CollectionsHaveToParArray ——————————————————————————–

def toParArray: ParArray[T]

• Implicit information
  • This member is added by an implicit conversion from ParHashSet [T] to CollectionsHaveToParArray [ParHashSet [T], T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type (ParHashSet [T]) ⇒ GenTraversableOnce [T] is in scope.
• Definition Classes
  • CollectionsHaveToParArray (added by implicit convertion: scala.collection.parallel.CollectionsHaveToParArray)

Full Source:

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala
package collection.parallel.immutable



import scala.collection.parallel.ParSetLike
import scala.collection.parallel.Combiner
import scala.collection.parallel.IterableSplitter
import scala.collection.mutable.UnrolledBuffer.Unrolled
import scala.collection.mutable.UnrolledBuffer
import scala.collection.generic.ParSetFactory
import scala.collection.generic.CanCombineFrom
import scala.collection.generic.GenericParTemplate
import scala.collection.generic.GenericParCompanion
import scala.collection.generic.GenericCompanion
import scala.collection.immutable.{ HashSet, TrieIterator }
import scala.collection.parallel.Task



/** Immutable parallel hash set, based on hash tries.
 *
 *  $paralleliterableinfo
 *
 *  $sideeffects
 *
 *  @tparam T    the element type of the set
 *
 *  @author Aleksandar Prokopec
 *  @since 2.9
 *  @see  [[http://docs.scala-lang.org/overviews/parallel-collections/concrete-parallel-collections.html#parallel_hash_tries Scala's Parallel Collections Library overview]]
 *  section on Parallel Hash Tries for more information.
 *
 *  @define Coll `immutable.ParHashSet`
 *  @define coll immutable parallel hash set
 */
@SerialVersionUID(1L)
class ParHashSet[T] private[immutable] (private[this] val trie: HashSet[T])
extends ParSet[T]
   with GenericParTemplate[T, ParHashSet]
   with ParSetLike[T, ParHashSet[T], HashSet[T]]
   with Serializable
{
self =>

  def this() = this(HashSet.empty[T])

  override def companion: GenericCompanion[ParHashSet] with GenericParCompanion[ParHashSet] = ParHashSet

  override def empty: ParHashSet[T] = new ParHashSet[T]

  def splitter: IterableSplitter[T] = new ParHashSetIterator(trie.iterator, trie.size)

  override def seq = trie

  def -(e: T) = new ParHashSet(trie - e)

  def +(e: T) = new ParHashSet(trie + e)

  def contains(e: T): Boolean = trie.contains(e)

  override def size = trie.size

  protected override def reuse[S, That](oldc: Option[Combiner[S, That]], newc: Combiner[S, That]) = oldc match {
    case Some(old) => old
    case None => newc
  }

  class ParHashSetIterator(var triter: Iterator[T], val sz: Int)
  extends IterableSplitter[T] {
    var i = 0
    def dup = triter match {
      case t: TrieIterator[_] =>
        dupFromIterator(t.dupIterator)
      case _ =>
        val buff = triter.toBuffer
        triter = buff.iterator
        dupFromIterator(buff.iterator)
    }
    private def dupFromIterator(it: Iterator[T]) = {
      val phit = new ParHashSetIterator(it, sz)
      phit.i = i
      phit
    }
    def split: Seq[IterableSplitter[T]] = if (remaining < 2) Seq(this) else triter match {
      case t: TrieIterator[_] =>
        val previousRemaining = remaining
        val ((fst, fstlength), snd) = t.split
        val sndlength = previousRemaining - fstlength
        Seq(
          new ParHashSetIterator(fst, fstlength),
          new ParHashSetIterator(snd, sndlength)
        )
      case _ =>
        // iterator of the collision map case
        val buff = triter.toBuffer
        val (fp, sp) = buff.splitAt(buff.length / 2)
        Seq(fp, sp) map { b => new ParHashSetIterator(b.iterator, b.length) }
    }
    def next(): T = {
      i += 1
      triter.next()
    }
    def hasNext: Boolean = {
      i < sz
    }
    def remaining = sz - i
  }

}


/** $factoryInfo
 *  @define Coll `immutable.ParHashSet`
 *  @define coll immutable parallel hash set
 */
object ParHashSet extends ParSetFactory[ParHashSet] {
  def newCombiner[T]: Combiner[T, ParHashSet[T]] = HashSetCombiner[T]

  implicit def canBuildFrom[T]: CanCombineFrom[Coll, T, ParHashSet[T]] =
    new GenericCanCombineFrom[T]

  def fromTrie[T](t: HashSet[T]) = new ParHashSet(t)
}


private[immutable] abstract class HashSetCombiner[T]
extends scala.collection.parallel.BucketCombiner[T, ParHashSet[T], Any, HashSetCombiner[T]](HashSetCombiner.rootsize) {
//self: EnvironmentPassingCombiner[T, ParHashSet[T]] =>
  import HashSetCombiner._
  val emptyTrie = HashSet.empty[T]

  def +=(elem: T) = {
    sz += 1
    val hc = emptyTrie.computeHash(elem)
    val pos = hc & 0x1f
    if (buckets(pos) eq null) {
      // initialize bucket
      buckets(pos) = new UnrolledBuffer[Any]
    }
    // add to bucket
    buckets(pos) += elem
    this
  }

  def result = {
    val bucks = buckets.filter(_ != null).map(_.headPtr)
    val root = new Array[HashSet[T]](bucks.length)

    combinerTaskSupport.executeAndWaitResult(new CreateTrie(bucks, root, 0, bucks.length))

    var bitmap = 0
    var i = 0
    while (i < rootsize) {
      if (buckets(i) ne null) bitmap |= 1 << i
      i += 1
    }
    val sz = root.foldLeft(0)(_ + _.size)

    if (sz == 0) new ParHashSet[T]
    else if (sz == 1) new ParHashSet[T](root(0))
    else {
      val trie = new HashSet.HashTrieSet(bitmap, root, sz)
      new ParHashSet[T](trie)
    }
  }

  /* tasks */

  class CreateTrie(bucks: Array[Unrolled[Any]], root: Array[HashSet[T]], offset: Int, howmany: Int)
  extends Task[Unit, CreateTrie] {
    var result = ()
    def leaf(prev: Option[Unit]) = {
      var i = offset
      val until = offset + howmany
      while (i < until) {
        root(i) = createTrie(bucks(i))
        i += 1
      }
    }
    private def createTrie(elems: Unrolled[Any]): HashSet[T] = {
      var trie = new HashSet[T]

      var unrolled = elems
      var i = 0
      while (unrolled ne null) {
        val chunkarr = unrolled.array
        val chunksz = unrolled.size
        while (i < chunksz) {
          val v = chunkarr(i).asInstanceOf[T]
          val hc = trie.computeHash(v)
          trie = trie.updated0(v, hc, rootbits)  // internal API, private[collection]
          i += 1
        }
        i = 0
        unrolled = unrolled.next
      }

      trie
    }
    def split = {
      val fp = howmany / 2
      List(new CreateTrie(bucks, root, offset, fp), new CreateTrie(bucks, root, offset + fp, howmany - fp))
    }
    def shouldSplitFurther = howmany > scala.collection.parallel.thresholdFromSize(root.length, combinerTaskSupport.parallelismLevel)
  }
}


object HashSetCombiner {
  def apply[T] = new HashSetCombiner[T] {} // was: with EnvironmentPassingCombiner[T, ParHashSet[T]] {}

  private[immutable] val rootbits = 5
  private[immutable] val rootsize = 1 << 5
}