Scala Library: scala.collection.parallel.ParIterableLike
scala.collection.parallel.ParIterableLike
A template trait for parallel collections of type ParIterable[T]
.
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:
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:
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:
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 collection
- Repr
- the type of the actual collection containing the elements
- Self Type
- ParIterableLike [T, Repr, Sequential]
- Source
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).
- type of the result of this method (
- Tp
- the representation type of the task at hand.
- Attributes
- protected
- Source
class Aggregate[S] extends Accessor[S, Aggregate[S]]
- Attributes
- protected[this]
- Source
trait BuilderOps[Elem, To] extends AnyRef
class Collect[S, That] extends Transformer[Combiner[S, That], Collect[S, That]]
- Attributes
- protected[this]
- Source
abstract class Composite[FR, SR, R, First <: StrictSplitterCheckTask[FR, _], Second <: StrictSplitterCheckTask[SR, _]] extends NonDivisibleTask[R, Composite[FR, SR, R, First, Second]]
- Attributes
- protected[this]
- Source
class Copy[U >: T, That] extends Transformer[Combiner[U, That], Copy[U, That]]
- Attributes
- protected
- Source
class CopyToArray[U >: T, This >: Repr] extends Accessor[Unit, CopyToArray[U, This]]
- Attributes
- protected[this]
- Source
class Count extends Accessor[Int, Count]
- Attributes
- protected[this]
- Source
class CreateScanTree[U >: T] extends Transformer[ScanTree[U], CreateScanTree[U]]
- Attributes
- protected[this]
- Source
class Drop[U >: T, This >: Repr] extends Transformer[Combiner[U, This], Drop[U, This]]
- Attributes
- protected[this]
- Source
class Exists extends Accessor[Boolean, Exists]
- Attributes
- protected[this]
- Source
class Filter[U >: T, This >: Repr] extends Transformer[Combiner[U, This], Filter[U, This]]
- Attributes
- protected[this]
- Source
class FilterNot[U >: T, This >: Repr] extends Transformer[Combiner[U, This], FilterNot[U, This]]
- Attributes
- protected[this]
- Source
class Find[U >: T] extends Accessor[Option[U], Find[U]]
- Attributes
- protected[this]
- Source
class FlatMap[S, That] extends Transformer[Combiner[S, That], FlatMap[S, That]]
- Attributes
- protected[this]
- Source
class Fold[U >: T] extends Accessor[U, Fold[U]]
- Attributes
- protected[this]
- Source
class Forall extends Accessor[Boolean, Forall]
- Attributes
- protected[this]
- Source
class Foreach[S] extends Accessor[Unit, Foreach[S]]
- Attributes
- protected[this]
- Source
class FromScanTree[U >: T, That] extends StrictSplitterCheckTask[Combiner[U, That], FromScanTree[U, That]]
- Attributes
- protected[this]
- Source
class GroupBy[K, U >: T] extends Transformer[HashMapCombiner[K, U], GroupBy[K, U]]
- Attributes
- protected[this]
- Source
class Map[S, That] extends Transformer[Combiner[S, That], Map[S, That]]
- Attributes
- protected[this]
- Source
class Max[U >: T] extends Accessor[Option[U], Max[U]]
- Attributes
- protected[this]
- Source
class Min[U >: T] extends Accessor[Option[U], Min[U]]
- Attributes
- protected[this]
- Source
trait NonDivisible[R] extends NonDivisibleTask[R, NonDivisible[R]]
- Attributes
- protected[this]
- Source
trait NonDivisibleTask[R, Tp] extends StrictSplitterCheckTask[R, Tp]
- Attributes
- protected[this]
- Source
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]
- Source
class Partition[U >: T, This >: Repr] extends Transformer[(Combiner[U, This], Combiner[U, This]), Partition[U, This]]
- Attributes
- protected[this]
- Source
class Product[U >: T] extends Accessor[U, Product[U]]
- Attributes
- protected[this]
- Source
class Reduce[U >: T] extends Accessor[Option[U], Reduce[U]]
- Attributes
- protected[this]
- Source
abstract class ResultMapping[R, Tp, R1] extends NonDivisibleTask[R1, ResultMapping[R, Tp, R1]]
- Attributes
- protected[this]
- Source
type SSCTask[R, Tp] = StrictSplitterCheckTask[R, Tp]
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]
- Source
case class ScanNode[U >: T](left: ScanTree[U], right: ScanTree[U]) extends ScanTree[U] with scala.Product with Serializable
- Attributes
- protected[this]
- Source
trait ScanTree[U >: T] extends AnyRef
- Attributes
- protected[this]
- Source
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]
- Source
trait SignallingOps[PI <: DelegatedSignalling] extends AnyRef
class Slice[U >: T, This >: Repr] extends Transformer[Combiner[U, This], Slice[U, This]]
- Attributes
- protected[this]
- Source
class Span[U >: T, This >: Repr] extends Transformer[(Combiner[U, This], Combiner[U, This]), Span[U, This]]
- Attributes
- protected[this]
- Source
class SplitAt[U >: T, This >: Repr] extends Transformer[(Combiner[U, This], Combiner[U, This]), SplitAt[U, This]]
- Attributes
- protected[this]
- Source
trait StrictSplitterCheckTask[R, Tp] extends Task[R, Tp]
- Attributes
- protected
- Source
class Sum[U >: T] extends Accessor[U, Sum[U]]
- Attributes
- protected[this]
- Source
class Take[U >: T, This >: Repr] extends Transformer[Combiner[U, This], Take[U, This]]
- Attributes
- protected[this]
- Source
class TakeWhile[U >: T, This >: Repr] extends Transformer[(Combiner[U, This], Boolean), TakeWhile[U, This]]
- Attributes
- protected[this]
- Source
trait TaskOps[R, Tp] extends AnyRef
class ToParCollection[U >: T, That] extends Transformer[Combiner[U, That], ToParCollection[U, That]]
- Attributes
- protected[this]
- Source
class ToParMap[K, V, That] extends Transformer[Combiner[(K, V), That], ToParMap[K, V, That]]
- Attributes
- protected[this]
- Source
trait Transformer[R, Tp] extends Accessor[R, Tp]
- Attributes
- protected
- Source
class Zip[U >: T, S, That] extends Transformer[Combiner[(U, S), That], Zip[U, S, That]]
- Attributes
- protected[this]
- Source
class ZipAll[U >: T, S, That] extends Transformer[Combiner[(U, S), That], ZipAll[U, S, That]]
- Attributes
- protected[this]
- Source
Concrete Value Members From scala.collection.CustomParallelizable
def parCombiner: Combiner[T, Repr]
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
- a combiner for the parallel collection of type
- Attributes
- protected[this]
- Definition Classes
- CustomParallelizable → Parallelizable
(defined at scala.collection.CustomParallelizable)
Abstract Value Members From scala.collection.generic.HasNewCombiner
abstract def newCombiner: Combiner[T, Repr]
- Attributes
- protected[this]
- Definition Classes
- HasNewCombiner
(defined at scala.collection.generic.HasNewCombiner)
Abstract Value Members From scala.collection.parallel.ParIterableLike
abstract 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
- Attributes
- protected[scala.collection.parallel]
(defined at scala.collection.parallel.ParIterableLike)
Concrete Value Members From scala.collection.parallel.ParIterableLike
abstract def seq: Sequential
- Definition Classes
- ParIterableLike → Parallelizable → GenTraversableOnce
(defined at scala.collection.parallel.ParIterableLike)
def ++[U >: T, That](that: GenTraversableOnce[U])(implicit bf: CanBuildFrom[Repr, U, That]): That
[use case]
Returns a new parallel iterable containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the parallel iterable is the most specific superclass encompassing the element types of the two operands.
Example:
- B
- the element type of the returned collection.
- that
- the traversable to append.
- returns
- a new parallel iterable which contains all elements of this parallel
iterable followed by all elements of
that
.
- a new parallel iterable which contains all elements of this parallel
iterable followed by all elements of
- 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.
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 valuez
on the left:
- the result of inserting
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.
- 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 valuez
on the right:
- the result of inserting
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.
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 or0
for summation) and may be evaluated more than once
- the initial value for the accumulated result of the partition - this will
typically be the neutral element for the
- 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[Repr, S, That]): CanBuildFrom[Sequential, S, That]
- Attributes
- protected[this]
(defined at scala.collection.parallel.ParIterableLike)
implicit def builder2ops[Elem, To](cb: Builder[Elem, To]): BuilderOps[Elem, To]
- Attributes
- protected
(defined at scala.collection.parallel.ParIterableLike)
def canEqual(other: Any): Boolean
(defined at scala.collection.parallel.ParIterableLike)
def collect[S, That](pf: PartialFunction[T, S])(implicit bf: CanBuildFrom[Repr, S, That]): That
[use case]
Builds a new collection by applying a partial function to all elements of this parallel iterable on which the function is defined.
- B
- the element type of the returned collection.
- pf
- the partial function which filters and maps the parallel iterable.
- returns
- a new parallel iterable 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.
- a new parallel iterable resulting from applying the given partial function
- Definition Classes
- ParIterableLike → GenTraversableLike
(defined at scala.collection.parallel.ParIterableLike)
def combinerFactory: CombinerFactory[T, Repr]
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]
(defined at scala.collection.parallel.ParIterableLike)
def combinerFactory[S, That](cbf: () ⇒ Combiner[S, That]): CombinerFactory[S, That]
- Attributes
- protected[this]
(defined at scala.collection.parallel.ParIterableLike)
def copyToArray[U >: T](xs: Array[U]): Unit
[use case]
Copies the elements of this parallel iterable to an array. Fills the given array
xs
with values of this parallel iterable. Copying will stop once either the
end of the current parallel iterable 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 parallel iterable to an array. Fills the given array
xs
with values of this parallel iterable, beginning at index start
.
Copying will stop once either the end of the current parallel iterable 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 parallel iterable to an array. Fills the given array
xs
with at most len
elements of this parallel iterable, starting at
position start
. Copying will stop once either the end of the current parallel
iterable 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
.
- the number of elements satisfying the predicate
- Definition Classes
- ParIterableLike → GenTraversableOnce
(defined at scala.collection.parallel.ParIterableLike)
def debugBuffer: ArrayBuffer[String]
(defined at scala.collection.parallel.ParIterableLike)
implicit def delegatedSignalling2ops[PI <: DelegatedSignalling](it: PI): SignallingOps[PI]
- Attributes
- protected
(defined at scala.collection.parallel.ParIterableLike)
def drop(n: Int): Repr
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 thann
elements.
- a parallel iterable consisting of all elements of this parallel iterable
except the first
- Definition Classes
- ParIterableLike → GenTraversableLike
(defined at scala.collection.parallel.ParIterableLike)
def dropWhile(pred: (T) ⇒ Boolean): Repr
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
- a collection composed of all the elements after the longest prefix of
elements in this parallel iterable that satisfy the predicate
- 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
- true if
- Definition Classes
- ParIterableLike → GenTraversableOnce
(defined at scala.collection.parallel.ParIterableLike)
def filter(pred: (T) ⇒ Boolean): Repr
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.
- a new parallel iterable consisting of all elements of this parallel iterable
that satisfy the given predicate
- Definition Classes
- ParIterableLike → GenTraversableLike
(defined at scala.collection.parallel.ParIterableLike)
def filterNot(pred: (T) ⇒ Boolean): Repr
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.
- a new parallel iterable consisting of all elements of this parallel iterable
that do not satisfy the given predicate
- 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
- an option value with the element if such an element exists, or
- Definition Classes
- ParIterableLike → GenTraversableOnce
(defined at scala.collection.parallel.ParIterableLike)
def flatMap[S, That](f: (T) ⇒ GenTraversableOnce[S])(implicit bf: CanBuildFrom[Repr, S, That]): That
[use case]
Builds a new collection by applying a function to all elements of this parallel iterable and using the elements of the resulting collections.
For example:
The type of the resulting collection is guided by the static type of parallel iterable. This might cause unexpected results sometimes. For example:
- B
- the element type of the returned collection.
- f
- the function to apply to each element.
- returns
- a new parallel iterable resulting from applying the given collection-valued
function
f
to each element of this parallel iterable and concatenating the results.
- a new parallel iterable resulting from applying the given collection-valued
function
- 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 valuez
on the left:
- the result of inserting
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 valuez
on the right:
- the result of inserting
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
.
- a type parameter for the binary operator, a supertype of
- 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)
- 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.
- op
- a binary operator that must be associative
- returns
- the result of applying fold operator
op
between all the elements andz
- the result of applying fold operator
- 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
- true if
- 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): immutable.ParMap[K, Repr]
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:
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 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[Repr, S, That]): That
[use case]
Builds a new collection by applying a function to all elements of this parallel iterable.
- B
- the element type of the returned collection.
- f
- the function to apply to each element.
- returns
- a new parallel iterable resulting from applying the given function
f
to each element of this parallel iterable and collecting the results.
- a new parallel iterable resulting from applying the given function
- 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 parallel iterable 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 parallel iterable 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 stringsep
.
- a string representation of this parallel iterable. In the resulting string
the string representations (w.r.t. the method
- Definition Classes
- ParIterableLike → GenTraversableOnce
Example:
(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 stringend
. Inside, the string representations (w.r.t. the methodtoString
) of all elements of this parallel iterable are separated by the stringsep
.
- a string representation of this parallel iterable. The resulting string
begins with the string
- Definition Classes
- ParIterableLike → GenTraversableOnce
Example:
(defined at scala.collection.parallel.ParIterableLike)
def partition(pred: (T) ⇒ Boolean): (Repr, Repr)
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.
- a pair of parallel iterables: the first parallel iterable consists of all
elements that satisfy the predicate
- 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.
- an option value containing the result of
- Definition Classes
- ParIterableLike → GenTraversableOnce
(defined at scala.collection.parallel.ParIterableLike)
def reduceLeft[U >: T](op: (U, T) ⇒ U): U
(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
.
- A type parameter for the binary operator, a supertype of
- 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, andNone
otherwise.
- An option value containing result of applying reduce operator
- 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.
- an option value containing the result of
- 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:
- the result of inserting
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
.
- A type parameter for the binary operator, a supertype of
- 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.
- The result of applying reduce operator
- Definition Classes
- ParIterableLike → GenTraversableOnce
- Exceptions thrown
- UnsupportedOperationException if this parallel iterable is empty.
(defined at scala.collection.parallel.ParIterableLike)
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.
- The combiner that is the result of the previous task, or
- newc
- The new, empty combiner that can be used.
- returns
- Either
newc
oroldc
.
- Either
- Attributes
- protected
(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 parallel iterable.
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[Repr, 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
- neutral element for the operator
- op
- the associative operator for the scan
- returns
- a new parallel iterable containing the prefix scan of the elements in this parallel iterable
- Definition Classes
- ParIterableLike → GenTraversableLike
(defined at scala.collection.parallel.ParIterableLike)
def scanLeft[S, That](z: S)(op: (S, T) ⇒ S)(implicit bf: CanBuildFrom[Repr, 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 classThat
from the current representation typeRepr
and and the new element typeB
.
- an implicit value of class
- 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[Repr, 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:
- 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 classThat
from the current representation typeRepr
and and the new element typeB
.
- an implicit value of class
- returns
- collection with intermediate results
- Definition Classes
- ParIterableLike → GenTraversableLike
(defined at scala.collection.parallel.ParIterableLike)
def sequentially[S, That <: Parallel](b: (Sequential) ⇒ Parallelizable[S, That]): Repr
- Attributes
- protected[this]
(defined at scala.collection.parallel.ParIterableLike)
def slice(unc_from: Int, unc_until: Int): Repr
Selects an interval of elements. The returned collection is made up of all
elements x
which satisfy the invariant:
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) indexuntil
of this parallel iterable.
- a parallel iterable containing the elements greater than or equal to index
- Definition Classes
- ParIterableLike → GenTraversableLike
(defined at scala.collection.parallel.ParIterableLike)
def span(pred: (T) ⇒ Boolean): (Repr, Repr)
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
- a pair consisting of the longest prefix of the collection for which all the
elements satisfy
- Definition Classes
- ParIterableLike → GenTraversableLike
(defined at scala.collection.parallel.ParIterableLike)
def splitAt(n: Int): (Repr, Repr)
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.
- a pair of parallel iterables consisting of the first
- Definition Classes
- ParIterableLike → GenTraversableLike
(defined at scala.collection.parallel.ParIterableLike)
def take(n: Int): Repr
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 thann
elements.
- a parallel iterable consisting only of the first
- Definition Classes
- ParIterableLike → GenTraversableLike
(defined at scala.collection.parallel.ParIterableLike)
def takeWhile(pred: (T) ⇒ Boolean): Repr
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
- the longest prefix of this parallel iterable of elements that satisfy the
predicate
- Definition Classes
- ParIterableLike → GenTraversableLike
(defined at scala.collection.parallel.ParIterableLike)
implicit def task2ops[R, Tp](tsk: SSCTask[R, Tp]): TaskOps[R, Tp]
- Attributes
- protected
(defined at scala.collection.parallel.ParIterableLike)
def tasksupport: TaskSupport
The task support object which is responsible for scheduling and load-balancing tasks to processors.
- 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:
- 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 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.
- an
- 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)]): immutable.ParMap[K, V]
[use case]
Converts this parallel iterable 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 parallel iterable.
- a map of type
- Definition Classes
- ParIterableLike → GenTraversableOnce
(defined at scala.collection.parallel.ParIterableLike)
def toParCollection[U >: T, That](cbf: () ⇒ Combiner[U, That]): That
- Attributes
- protected
(defined at scala.collection.parallel.ParIterableLike)
def toParMap[K, V, That](cbf: () ⇒ Combiner[(K, V), That])(implicit ev: <:<[T, (K, V)]): That
- Attributes
- protected
(defined at scala.collection.parallel.ParIterableLike)
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
- ParIterableLike → GenTraversableOnce
(defined at scala.collection.parallel.ParIterableLike)
def toSet[U >: T]: immutable.ParSet[U]
Converts this parallel iterable to a set.
Note: will not terminate for infinite-sized collections.
- returns
- a set containing all elements of this parallel iterable.
- Definition Classes
- ParIterableLike → GenTraversableOnce
(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): Repr
(defined at scala.collection.parallel.ParIterableLike)
def wrap[R](body: ⇒ R): NonDivisible[R]
- Attributes
- protected
(defined at scala.collection.parallel.ParIterableLike)
def zipAll[S, U >: T, That](that: GenIterable[S], thisElem: U, thatElem: S)(implicit bf: CanBuildFrom[Repr, (U, S), That]): That
[use case]
Returns a parallel iterable formed from this parallel iterable 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 parallel iterable is
shorter than
that
.
- the element to be used to fill up the result if this parallel iterable is
shorter than
- thatElem
- the element to be used to fill up the result if
that
is shorter than this parallel iterable.
- the element to be used to fill up the result if
- returns
- a new parallel iterable containing pairs consisting of corresponding
elements of this parallel iterable and
that
. The length of the returned collection is the maximum of the lengths of this parallel iterable andthat
. If this parallel iterable is shorter thanthat
,thisElem
values are used to pad the result. Ifthat
is shorter than this parallel iterable,thatElem
values are used to pad the result.
- a new parallel iterable containing pairs consisting of corresponding
elements of this parallel iterable and
- Definition Classes
- ParIterableLike → GenIterableLike
(defined at scala.collection.parallel.ParIterableLike)
def zipWithIndex[U >: T, That](implicit bf: CanBuildFrom[Repr, (U, Int), That]): That
[use case]
Zips this parallel iterable with its indices.
Note: might return different results for different runs, unless the underlying collection type is ordered.
- returns
- A new parallel iterable containing pairs consisting of all elements of this
parallel iterable paired with their index. Indices start at
0
.
- A new parallel iterable containing pairs consisting of all elements of this
parallel iterable paired with their index. Indices start at
- Definition Classes
- ParIterableLike → GenIterableLike
Example:
(defined at scala.collection.parallel.ParIterableLike)
def zip[U >: T, S, That](that: GenIterable[S])(implicit bf: CanBuildFrom[Repr, (U, S), That]): That
[use case]
Returns a parallel iterable formed from this parallel iterable 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 parallel iterable containing pairs consisting of corresponding
elements of this parallel iterable and
that
. The length of the returned collection is the minimum of the lengths of this parallel iterable andthat
.
- a new parallel iterable containing pairs consisting of corresponding
elements of this parallel iterable and
- Definition Classes
- ParIterableLike → GenIterableLike
(defined at scala.collection.parallel.ParIterableLike)
Deprecated Value Members From scala.collection.parallel.ParIterableLike
def view: IterableView[T, Sequential]
- Annotations
- @ deprecated
- Deprecated
- (Since version 2.11.0) Use.seq.view instead
(defined at scala.collection.parallel.ParIterableLike)
Concrete Value Members From Implicit scala.collection.parallel.CollectionsHaveToParArray ——————————————————————————–
def toParArray: ParArray[T]
- Implicit information
- This member is added by an implicit conversion from ParIterableLike [T, Repr, Sequential] to CollectionsHaveToParArray [ParIterableLike [T, Repr, Sequential], T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type (ParIterableLike [T, Repr, Sequential]) ⇒ GenTraversableOnce [T] is in scope.
- Definition Classes
- CollectionsHaveToParArray (added by implicit convertion: scala.collection.parallel.CollectionsHaveToParArray)
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