scala.collection.parallel.immutable
the sequential range this parallel range was obtained from
Standard accessor task that iterates over the elements of the collection.
Used to iterate elements using indices
Performs two tasks in parallel, and waits for both to finish.
Sequentially performs one task after another.
Test two objects for inequality.
Test two objects for inequality.
true if !(this == that), false otherwise.
Equivalent to x.hashCode except for boxed numeric types and null.
Equivalent to x.hashCode except for boxed numeric types and null.
For numerics, it returns a hash value which is consistent
with value equality: if two value type instances compare
as true, then ## will produce the same hash value for each
of them.
For null returns a hashcode where null.hashCode throws a
NullPointerException.
a hash value consistent with ==
[use case] Returns a new immutable parallel range containing the elements from the left hand operand followed by the elements from the right hand operand.
Returns a new immutable parallel range containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the immutable parallel range is the most specific superclass encompassing the element types of the two operands.
Example:
scala> val a = LinkedList(1) a: scala.collection.mutable.LinkedList[Int] = LinkedList(1) scala> val b = LinkedList(2) b: scala.collection.mutable.LinkedList[Int] = LinkedList(2) scala> val c = a ++ b c: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2) scala> val d = LinkedList('a') d: scala.collection.mutable.LinkedList[Char] = LinkedList(a) scala> val e = c ++ d e: scala.collection.mutable.LinkedList[AnyVal] = LinkedList(1, 2, a)
the element type of the returned collection.
the traversable to append.
a new immutable parallel range which contains all elements of this immutable parallel range
followed by all elements of that.
[use case] A copy of the immutable parallel range with an element prepended.
A copy of the immutable parallel range with an element prepended.
Note that :-ending operators are right associative (see example).
A mnemonic for +: vs. :+ is: the COLon goes on the COLlection side.
Also, the original immutable parallel range is not modified, so you will want to capture the result.
Example:
scala> val x = LinkedList(1) x: scala.collection.mutable.LinkedList[Int] = LinkedList(1) scala> val y = 2 +: x y: scala.collection.mutable.LinkedList[Int] = LinkedList(2, 1) scala> println(x) LinkedList(1)
the prepended element
a new immutable parallel range consisting of elem followed
by all elements of this immutable parallel range.
Applies a binary operator to a start value and all elements of this immutable parallel range, going left to right.
Applies a binary operator to a start value and all elements of this immutable parallel range, 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 = LinkedList(1,2,3,4) a: scala.collection.mutable.LinkedList[Int] = LinkedList(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.
the start value.
the binary operator.
the result of inserting op between consecutive elements of this immutable parallel range,
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 immutable parallel range.
[use case] A copy of this immutable parallel range with an element appended.
A copy of this immutable parallel range with an element appended.
A mnemonic for +: vs. :+ is: the COLon goes on the COLlection side.
Note: will not terminate for infinite-sized collections.
Example:
scala> import scala.collection.mutable.LinkedList import scala.collection.mutable.LinkedList scala> val a = LinkedList(1) a: scala.collection.mutable.LinkedList[Int] = LinkedList(1) scala> val b = a :+ 2 b: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2) scala> println(a) LinkedList(1)
the appended element
a new immutable parallel range consisting of
all elements of this immutable parallel range followed by elem.
Applies a binary operator to all elements of this immutable parallel range and a start value, going right to left.
Applies a binary operator to all elements of this immutable parallel range 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 = LinkedList(1,2,3,4) a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4) scala> val b = (a :\ 5)(_+_) b: Int = 15 scala> val c = (a :\ 5)((x,y) => x + y) c: Int = 15
the start value
the binary operator
the result of inserting op between consecutive elements of this immutable parallel range,
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 immutable parallel range.
Test two objects for equality.
Test two objects for equality.
The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
true if the receiver object is equivalent to the argument; false otherwise.
Aggregates the results of applying an operator to subsequent elements.
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 list, while combop
would concatenate two lists 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).
the type of accumulated results
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)
an operator used to accumulate results within a partition
an associative operator used to combine results from different partitions
Selects an element by its index in the immutable parallel range.
Selects an element by its index in the immutable parallel range.
Example:
scala> val x = LinkedList(1, 2, 3, 4, 5) x: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4, 5) scala> x(3) res1: Int = 4
The index to select.
the element of this immutable parallel range at index idx, where 0 indicates the first element.
if idx does not satisfy 0 <= idx < length.
Cast the receiver object to be of type T0.
Cast the receiver object to be of type T0.
Note that the success of a cast at runtime is modulo Scala's erasure semantics.
Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at
runtime, while the expression List(1).asInstanceOf[List[String]] will not.
In the latter example, because the type argument is erased as part of compilation it is
not possible to check whether the contents of the list are of the requested type.
the receiver object.
if the receiver object is not an instance of the erasure of type T0.
Create a copy of the receiver object.
[use case] Builds a new collection by applying a partial function to all elements of this immutable parallel range on which the function is defined.
Builds a new collection by applying a partial function to all elements of this immutable parallel range on which the function is defined.
the element type of the returned collection.
the partial function which filters and maps the immutable parallel range.
a new immutable parallel range 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.
Creates a combiner factory.
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.
The factory companion object that builds instances of class immutable.ParRange.
The factory companion object that builds instances of class immutable.ParRange.
(or its Iterable superclass where class immutable.ParRange is not a Seq.)
[use case] Copies values of this immutable parallel range to an array.
Copies values of this immutable parallel range to an array.
Fills the given array xs with values of this immutable parallel range, beginning at index start.
Copying will stop once either the end of the current immutable parallel range is reached,
or the end of the array is reached.
Note: will not terminate for infinite-sized collections.
the array to fill.
the starting index.
[use case] Copies values of this immutable parallel range to an array.
Copies values of this immutable parallel range to an array.
Fills the given array xs with values of this immutable parallel range.
Copying will stop once either the end of the current immutable parallel range is reached,
or the end of the array is reached.
Note: will not terminate for infinite-sized collections.
the array to fill.
Tests whether every element of this immutable parallel range relates to the corresponding element of another parallel sequence by satisfying a test predicate.
Tests whether every element of this immutable parallel range relates to the corresponding element of another parallel sequence by satisfying a test predicate.
This method will use abort signalling capabilities. This means
that splitters may send and read abort signals.
the type of the elements of that
the other parallel sequence
the test predicate, which relates elements from both sequences
true if both parallel sequences have the same length and
p(x, y) is true for all corresponding elements x of this immutable parallel range
and y of that, otherwise false
Counts the number of elements in the immutable parallel range which satisfy a predicate.
Counts the number of elements in the immutable parallel range which satisfy a predicate.
the predicate used to test elements.
the number of elements satisfying the predicate p.
[use case] Computes the multiset difference between this immutable parallel range and another sequence.
Computes the multiset difference between this immutable parallel range and another sequence.
Note: will not terminate for infinite-sized collections.
the sequence of elements to remove
a new immutable parallel range which contains all elements of this immutable parallel range
except some of occurrences of elements that also appear in that.
If an element value x appears
n times in that, then the first n occurrences of x will not form
part of the result, but any following occurrences will.
Builds a new immutable parallel range from this immutable parallel range without any duplicate elements.
Builds a new immutable parallel range from this immutable parallel range without any duplicate elements.
Note: will not terminate for infinite-sized collections.
A new immutable parallel range which contains the first occurrence of every element of this immutable parallel range.
Selects all elements except first n ones.
Selects all elements except first n ones.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the number of elements to drop from this immutable parallel range.
a immutable parallel range consisting of all elements of this immutable parallel range except the first n ones, or else the
empty immutable parallel range, if this immutable parallel range has less than n elements.
Drops all elements in the longest prefix of elements that satisfy the predicate, and returns a collection composed of the remaining elements.
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.
the predicate used to test the elements
a collection composed of all the elements after the longest prefix of elements
in this immutable parallel range that satisfy the predicate pred
Tests whether this immutable parallel range ends with the given parallel sequence.
Tests whether this immutable parallel range ends with the given parallel sequence.
This method will use abort signalling capabilities. This means
that splitters may send and read abort signals.
the type of the elements of that sequence
the sequence to test
true if this immutable parallel range has that as a suffix, false otherwise
Tests whether the argument (arg0) is a reference to the receiver object (this).
Tests whether the argument (arg0) is a reference to the receiver object (this).
The eq method implements an equivalence relation on
non-null instances of AnyRef, and has three additional properties:
x and y of type AnyRef, multiple invocations of
x.eq(y) consistently returns true or consistently returns false.x of type AnyRef, x.eq(null) and null.eq(x) returns false.null.eq(null) returns true. When overriding the equals or hashCode methods, it is important to ensure that their behavior is
consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they
should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).
true if the argument is a reference to the receiver object; false otherwise.
The equals method for arbitrary sequences.
The equals method for arbitrary sequences. Compares this sequence to some other object.
The object to compare the sequence to
true if that is a sequence that has the same elements as
this sequence in the same order, false otherwise
Tests whether a predicate holds for some element of this immutable parallel range.
Tests whether a predicate holds for some element of this immutable parallel range.
This method will use abort signalling capabilities. This means
that splitters may send and read abort signals.
a predicate used to test elements
true if p holds for some element, false otherwise
Selects all elements of this immutable parallel range which satisfy a predicate.
Selects all elements of this immutable parallel range which satisfy a predicate.
the predicate used to test elements.
a new immutable parallel range consisting of all elements of this immutable parallel range that satisfy the given
predicate p. Their order may not be preserved.
Selects all elements of this immutable parallel range which do not satisfy a predicate.
Selects all elements of this immutable parallel range which do not satisfy a predicate.
the predicate used to test elements.
a new immutable parallel range consisting of all elements of this immutable parallel range that do not satisfy the given
predicate p. Their order may not be preserved.
Called by the garbage collector on the receiver object when there are no more references to the object.
Called by the garbage collector on the receiver object when there are no more references to the object.
The details of when and if the finalize method is invoked, as
well as the interaction between finalize and non-local returns
and exceptions, are all platform dependent.
Finds some element in the collection for which the predicate holds, if such an element exists.
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.
predicate used to test the elements
an option value with the element if such an element exists, or None otherwise
[use case] Builds a new collection by applying a function to all elements of this immutable parallel range and using the elements of the resulting collections.
Builds a new collection by applying a function to all elements of this immutable parallel range 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 range. 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 a 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)
the element type of the returned collection.
the function to apply to each element.
a new immutable parallel range resulting from applying the given collection-valued function
f to each element of this immutable parallel range and concatenating the results.
[use case] Converts this immutable parallel range of traversable collections into a immutable parallel range formed by the elements of these traversable collections.
Converts this immutable parallel range of traversable collections into a immutable parallel range formed by the elements of these traversable collections.
The resulting collection's type will be guided by the static type of immutable parallel range. For example:
val xs = List(Set(1, 2, 3), Set(1, 2, 3)) // xs == List(1, 2, 3, 1, 2, 3) val ys = Set(List(1, 2, 3), List(3, 2, 1)) // ys == Set(1, 2, 3)
the type of the elements of each traversable collection.
a new immutable parallel range resulting from concatenating all element immutable parallel ranges.
Folds the elements of this sequence using the specified associative binary operator.
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.
a type parameter for the binary operator, a supertype of T.
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 binary operator that must be associative
the result of applying fold operator op between all the elements and z
Applies a binary operator to a start value and all elements of this immutable parallel range, going left to right.
Applies a binary operator to a start value and all elements of this immutable parallel range, 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.
the start value.
the binary operator.
the result of inserting op between consecutive elements of this immutable parallel range,
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 immutable parallel range.
Applies a binary operator to all elements of this immutable parallel range and a start value, going right to left.
Applies a binary operator to all elements of this immutable parallel range 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.
the start value.
the binary operator.
the result of inserting op between consecutive elements of this immutable parallel range,
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 immutable parallel range.
Tests whether a predicate holds for all elements of this immutable parallel range.
Tests whether a predicate holds for all elements of this immutable parallel range.
This method will use abort signalling capabilities. This means
that splitters may send and read abort signals.
a predicate used to test elements
true if p holds for all elements, false otherwise
Applies a function f to all the elements of immutable parallel range in a undefined order.
Applies a function f to all the elements of immutable parallel range in a undefined order.
the result type of the function applied to each element, which is always discarded
function applied to each element
Returns string formatted according to given format string.
Returns string formatted according to given format string.
Format strings are as for String.format
(@see java.lang.String.format).
The generic builder that builds instances of immutable.ParRange
at arbitrary element types.
The generic builder that builds instances of immutable.ParRange
at arbitrary element types.
A representation that corresponds to the dynamic class of the receiver object.
A representation that corresponds to the dynamic class of the receiver object.
The nature of the representation is platform dependent.
a representation that corresponds to the dynamic class of the receiver object.
not specified by SLS as a member of AnyRef
Partitions this immutable parallel range into a map of immutable parallel ranges according to some discriminator function.
Partitions this immutable parallel range into a map of immutable parallel ranges 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 immutable parallel range.
the type of keys returned by the discriminator function.
the discriminator function.
A map from keys to immutable parallel ranges such that the following invariant holds:
(xs partition f)(k) = xs filter (x => f(x) == k) That is, every key k is bound to a immutable parallel range of those elements x
for which f(x) equals k.
Hashcodes for immutable.ParRange produce a value from the hashcodes of all the
elements of the immutable parallel range.
Hashcodes for immutable.ParRange produce a value from the hashcodes of all the
elements of the immutable parallel range.
the hash code value for this object.
Selects the first element of this immutable parallel range.
Selects the first element of this immutable parallel range.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the first element of this immutable parallel range.
if the immutable parallel range is empty.
Optionally selects the first element.
Optionally selects the first element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the first element of this immutable parallel range if it is nonempty,
None if it is empty.
[use case] Finds index of first occurrence of some value in this immutable parallel range after or at some start index.
Finds index of first occurrence of some value in this immutable parallel range after or at some start index.
Note: may not terminate for infinite-sized collections.
the element value to search for.
the start index
the index >= from of the first element of this immutable parallel range that is equal (as determined by ==)
to elem, or -1, if none exists.
[use case] Finds index of first occurrence of some value in this immutable parallel range.
Finds index of first occurrence of some value in this immutable parallel range.
Note: may not terminate for infinite-sized collections.
the element value to search for.
the index of the first element of this immutable parallel range that is equal (as determined by ==)
to elem, or -1, if none exists.
Finds the first element satisfying some predicate.
Finds the first element satisfying some 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.
the predicate used to test the elements
the starting offset for the search
the index >= from of the first element of this immutable parallel range that satisfies the predicate p,
or -1, if none exists
Finds index of first element satisfying some predicate.
Finds index of first element satisfying some predicate.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
the index of the first element of this immutable parallel range that satisfies the predicate p,
or -1, if none exists.
Selects all elements except the last.
Selects all elements except the last.
Note: might return different results for different runs, unless the underlying collection type is ordered.
a immutable parallel range consisting of all elements of this immutable parallel range except the last one.
if the immutable parallel range is empty.
[use case] Computes the multiset intersection between this immutable parallel range and another sequence.
Computes the multiset intersection between this immutable parallel range and another sequence.
Note: may not terminate for infinite-sized collections.
the sequence of elements to intersect with.
a new immutable parallel range which contains all elements of this immutable parallel range
which also appear in that.
If an element value x appears
n times in that, then the first n occurrences of x will be retained
in the result, but any following occurrences will be omitted.
Tests whether this immutable parallel range contains given index.
Tests whether this immutable parallel range contains given index.
The implementations of methods apply and isDefinedAt turn a Seq[A] into
a PartialFunction[Int, A].
the index to test
true if this immutable parallel range contains an element at position idx, false otherwise.
Tests whether the immutable parallel range is empty.
Tests whether the immutable parallel range is empty.
true if the immutable parallel range contains no elements, false otherwise.
Test whether the dynamic type of the receiver object is T0.
Test whether the dynamic type of the receiver object is T0.
Note that the result of the test is modulo Scala's erasure semantics.
Therefore the expression 1.isInstanceOf[String] will return false, while the
expression List(1).isInstanceOf[List[String]] will return true.
In the latter example, because the type argument is erased as part of compilation it is
not possible to check whether the contents of the list are of the specified type.
true if the receiver object is an instance of erasure of type T0; false otherwise.
Denotes whether this parallel collection has strict splitters.
Denotes whether this parallel collection has strict splitters.
This is true in general, and specific collection instances may choose to
override this method. Such collections will fail to execute methods
which rely on splitters being strict, i.e. returning a correct value
in the remaining method.
This method helps ensure that such failures occur on method invocations, rather than later on and in unpredictable ways.
Tests whether this immutable parallel range can be repeatedly traversed.
Tests whether this immutable parallel range can be repeatedly traversed.
true
Creates a new split iterator used to traverse the elements of this collection.
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.
a split iterator
Selects the last element.
Selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
The last element of this immutable parallel range.
If the immutable parallel range is empty.
[use case] Finds index of last occurrence of some value in this immutable parallel range before or at a given end index.
Finds index of last occurrence of some value in this immutable parallel range before or at a given end index.
the element value to search for.
the end index.
the index <= end of the last element of this immutable parallel range that is equal (as determined by ==)
to elem, or -1, if none exists.
[use case] Finds index of last occurrence of some value in this immutable parallel range.
Finds index of last occurrence of some value in this immutable parallel range.
Note: will not terminate for infinite-sized collections.
the element value to search for.
the index of the last element of this immutable parallel range that is equal (as determined by ==)
to elem, or -1, if none exists.
Finds the last element satisfying some predicate.
Finds the last element satisfying some 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 minimum integer value.
the predicate used to test the elements
the maximum offset for the search
the index <= end of the first element of this immutable parallel range that satisfies the predicate p,
or -1, if none exists
Finds index of last element satisfying some predicate.
Finds index of last element satisfying some predicate.
Note: will not terminate for infinite-sized collections.
the predicate used to test elements.
the index of the last element of this immutable parallel range that satisfies the predicate p,
or -1, if none exists.
Optionally selects the last element.
Optionally selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the last element of this immutable parallel range$ if it is nonempty,
None if it is empty.
The length of the immutable parallel range.
The length of the immutable parallel range.
Note: will not terminate for infinite-sized collections.
Note: xs.length and xs.size yield the same result.
the number of elements in this immutable parallel range.
[use case] Builds a new collection by applying a function to all elements of this immutable parallel range.
Builds a new collection by applying a function to all elements of this immutable parallel range.
the element type of the returned collection.
the function to apply to each element.
a new immutable parallel range resulting from applying the given function
f to each element of this immutable parallel range and collecting the results.
[use case] Finds the largest element.
Finds the largest element.
the largest element of this immutable parallel range.
[use case] Finds the smallest element.
Finds the smallest element.
the smallest element of this immutable parallel range
Displays all elements of this immutable parallel range in a string.
Displays all elements of this immutable parallel range in a string.
a string representation of this immutable parallel range. In the resulting string
the string representations (w.r.t. the method toString)
of all elements of this immutable parallel range follow each other without any
separator string.
Displays all elements of this immutable parallel range in a string using a separator string.
Displays all elements of this immutable parallel range in a string using a separator string.
the separator string.
a string representation of this immutable parallel range. In the resulting string
the string representations (w.r.t. the method toString)
of all elements of this immutable parallel range are separated by the string sep.
List(1, 2, 3).mkString("|") = "1|2|3"
Displays all elements of this immutable parallel range in a string using start, end, and separator strings.
Displays all elements of this immutable parallel range in a string using start, end, and separator strings.
the starting string.
the separator string.
the ending string.
a string representation of this immutable parallel range. 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 immutable parallel range are separated by
the string sep.
List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
Equivalent to !(this eq that).
Equivalent to !(this eq that).
true if the argument is not a reference to the receiver object; false otherwise.
The builder that builds instances of type immutable.ParRange[A]
The builder that builds instances of type immutable.ParRange[A]
Tests whether the immutable parallel range is not empty.
Tests whether the immutable parallel range is not empty.
true if the immutable parallel range contains at least one element, false otherwise.
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up a single thread that is waiting on the receiver object's monitor.
not specified by SLS as a member of AnyRef
Wakes up all threads that are waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
not specified by SLS as a member of AnyRef
[use case] A copy of this immutable parallel range with an element value appended until a given target length is reached.
A copy of this immutable parallel range with an element value appended until a given target length is reached.
the target length
the padding value
a new immutable parallel range consisting of
all elements of this immutable parallel range followed by the minimal number of occurrences of elem so
that the resulting immutable parallel range has a length of at least len.
Returns a parallel implementation of this collection.
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.
a parallel implementation of this collection
The default par implementation uses the combiner provided by this method
to create a new parallel collection.
The default par implementation uses the combiner provided by this method
to create a new parallel collection.
a combiner for the parallel collection of type ParRepr
Partitions this immutable parallel range in two immutable parallel ranges according to a predicate.
Partitions this immutable parallel range in two immutable parallel ranges according to a predicate.
the predicate on which to partition.
a pair of immutable parallel ranges: the first immutable parallel range consists of all elements that
satisfy the predicate p and the second immutable parallel range consists of all elements
that don't. The relative order of the elements in the resulting immutable parallel ranges
may not be preserved.
[use case] Produces a new immutable parallel range where a slice of elements in this immutable parallel range is replaced by another sequence.
Produces a new immutable parallel range where a slice of elements in this immutable parallel range is replaced by another sequence.
the index of the first replaced element
the number of elements to drop in the original immutable parallel range
a new immutable parallel range consisting of all elements of this immutable parallel range
except that replaced elements starting from from are replaced
by patch.
Returns the length of the longest prefix whose elements all satisfy some predicate.
Returns the length of the longest prefix whose elements all satisfy some predicate.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
the length of the longest prefix of this immutable parallel range
such that every element of the segment satisfies the predicate p.
[use case] Multiplies up the elements of this collection.
Multiplies up the elements of this collection.
the product of all elements in this immutable parallel range of numbers of type Int.
Instead of Int, any other type T with an implicit Numeric[T] implementation
can be used as element type of the immutable parallel range and as result type of product.
Examples of such types are: Long, Float, Double, BigInt.
the sequential range this parallel range was obtained from
Reduces the elements of this sequence using the specified associative binary operator.
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.
A type parameter for the binary operator, a supertype of T.
A binary operator that must be associative.
The result of applying reduce operator op between all the elements if the collection is nonempty.
if this immutable parallel range is empty.
Optionally applies a binary operator to all elements of this immutable parallel range, going left to right.
Optionally applies a binary operator to all elements of this immutable parallel range, 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.
the binary operator.
an option value containing the result of reduceLeft(op) is this immutable parallel range is nonempty,
None otherwise.
Optionally reduces the elements of this sequence using the specified associative binary operator.
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.
A type parameter for the binary operator, a supertype of T.
A binary operator that must be associative.
An option value containing result of applying reduce operator op between all
the elements if the collection is nonempty, and None otherwise.
Applies a binary operator to all elements of this immutable parallel range, going right to left.
Applies a binary operator to all elements of this immutable parallel range, 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.
the binary operator.
the result of inserting op between consecutive elements of this immutable parallel range,
going right to left:
op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...)) where x1, ..., xn are the elements of this immutable parallel range.
if this immutable parallel range is empty.
Optionally applies a binary operator to all elements of this immutable parallel range, going right to left.
Optionally applies a binary operator to all elements of this immutable parallel range, 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.
the binary operator.
an option value containing the result of reduceRight(op) is this immutable parallel range is nonempty,
None otherwise.
Optionally reuses an existing combiner for better performance.
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).
The combiner that is the result of the previous task, or None if there was no previous task.
The new, empty combiner that can be used.
Either newc or oldc.
Returns new immutable parallel range wih elements in reversed order.
Returns new immutable parallel range wih elements in reversed order.
Note: will not terminate for infinite-sized collections.
A new immutable parallel range with all elements of this immutable parallel range in reversed order.
[use case] Builds a new collection by applying a function to all elements of this immutable parallel range and collecting the results in reversed order.
Builds a new collection by applying a function to all elements of this immutable parallel range and collecting the results in reversed order.
Note: will not terminate for infinite-sized collections.
Note: xs.reverseMap(f) is the same as xs.reverse.map(f) but might be more efficient.
the element type of the returned collection.
the function to apply to each element.
a new immutable parallel range resulting from applying the given function
f to each element of this immutable parallel range and collecting the results in reversed order.
[use case] Checks if the other iterable collection contains the same elements in the same order as this immutable parallel range.
Checks if the other iterable collection contains the same elements in the same order as this immutable parallel range.
Note: might return different results for different runs, unless the underlying collection type is ordered.
Note: will not terminate for infinite-sized collections.
the collection to compare with.
true, if both collections contain the same elements in the same order, false otherwise.
[use case] Computes a prefix scan of the elements of the collection.
Computes a prefix scan of the elements of the collection.
Note: The neutral element z may be applied more than once.
neutral element for the operator op
the associative operator for the scan
a new immutable parallel range containing the prefix scan of the elements in this immutable parallel range
Produces a collection containing cumulative results of applying the operator going left to right.
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.
the actual type of the resulting collection
the initial value
the binary operator applied to the intermediate result and the element
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.
collection with intermediate results
Produces a collection containing cumulative results of applying the operator going right to left.
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)
the actual type of the resulting collection
the initial value
the binary operator applied to the intermediate result and the element
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.
collection with intermediate results
Returns the length of the longest segment of elements starting at a given position satisfying some predicate.
Returns the length of the longest segment of elements starting at a given position satisfying some 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.
the predicate used to test the elements
the starting offset for the search
the length of the longest segment of elements starting at from and
satisfying the predicate
The size of this immutable parallel range.
The size of this immutable parallel range.
Note: will not terminate for infinite-sized collections.
the number of elements in this immutable parallel range.
Selects an interval of elements.
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.
the lowest index to include from this immutable parallel range.
the lowest index to EXCLUDE from this immutable parallel range.
a immutable parallel range containing the elements greater than or equal to
index from extending up to (but not including) index until
of this immutable parallel range.
Splits this immutable parallel range into a prefix/suffix pair according to a predicate.
Splits this immutable parallel range 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.
the predicate used to test the elements
a pair consisting of the longest prefix of the collection for which all
the elements satisfy pred, and the rest of the collection
Splits this immutable parallel range into two at a given position.
Splits this immutable parallel range 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.
the position at which to split.
a pair of immutable parallel ranges consisting of the first n
elements of this immutable parallel range, and the other elements.
A more refined version of the iterator found in the ParallelIterable trait,
this iterator can be split into arbitrary subsets of iterators.
A more refined version of the iterator found in the ParallelIterable trait,
this iterator can be split into arbitrary subsets of iterators.
an iterator that can be split into subsets of precise size
Tests whether this immutable parallel range contains the given sequence at a given index.
Tests whether this immutable parallel range contains the given sequence at a given index.
This method will use abort signalling capabilities. This means
that splitters may send and read abort signals.
the element type of that parallel sequence
the parallel sequence this sequence is being searched for
the starting offset for the search
true if there is a sequence that starting at offset in this sequence, false otherwise
Tests whether this immutable parallel range starts with the given sequence.
Tests whether this immutable parallel range starts with the given sequence.
the sequence to test
true if this collection has that as a prefix, false otherwise.
Defines the prefix of this object's toString representation.
Defines the prefix of this object's toString representation.
a string representation which starts the result of toString
applied to this immutable parallel range. By default the string prefix is the
simple name of the collection class immutable parallel range.
[use case] Sums up the elements of this collection.
Sums up the elements of this collection.
the sum of all elements in this immutable parallel range of numbers of type Int.
Instead of Int, any other type T with an implicit Numeric[T] implementation
can be used as element type of the immutable parallel range and as result type of sum.
Examples of such types are: Long, Float, Double, BigInt.
Selects all elements except the first.
Selects all elements except the first.
Note: might return different results for different runs, unless the underlying collection type is ordered.
a immutable parallel range consisting of all elements of this immutable parallel range except the first one.
if the immutable parallel range is empty.
Selects first n elements.
Selects first n elements.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the number of elements to take from this immutable parallel range.
a immutable parallel range consisting only of the first n elements of this immutable parallel range,
or else the whole immutable parallel range, if it has less than n elements.
Takes the longest prefix of elements that satisfy the predicate.
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.
the predicate used to test the elements
the longest prefix of this immutable parallel range of elements that satisy the predicate pred
The task support object which is responsible for scheduling and load-balancing tasks to processors.
The task support object which is responsible for scheduling and load-balancing tasks to processors.
Changes the task support object which is responsible for scheduling and load-balancing tasks to processors.
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 scala.concurrent.forkjoin.ForkJoinPool(2))
[use case] Converts this immutable parallel range into another by copying all elements.
Converts this immutable parallel range into another by copying all elements.
Note: will not terminate for infinite-sized collections.
The collection type to build.
a new collection containing all elements of this immutable parallel range.
[use case] Converts this immutable parallel range to an array.
Converts this immutable parallel range to an array.
Note: will not terminate for infinite-sized collections.
an array containing all elements of this immutable parallel range.
An ClassTag must be available for the element type of this immutable parallel range.
Converts this immutable parallel range to a mutable buffer.
Converts this immutable parallel range to a mutable buffer.
Note: will not terminate for infinite-sized collections.
a buffer containing all elements of this immutable parallel range.
Converts this immutable parallel range to an indexed sequence.
Converts this immutable parallel range to an indexed sequence.
Note: will not terminate for infinite-sized collections.
an indexed sequence containing all elements of this immutable parallel range.
Converts this immutable parallel range to an iterable collection.
Converts this immutable parallel range 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.
an Iterable containing all elements of this immutable parallel range.
Returns an Iterator over the elements in this immutable parallel range.
Returns an Iterator over the elements in this immutable parallel range. Will return the same Iterator if this instance is already an Iterator.
Note: will not terminate for infinite-sized collections.
an Iterator containing all elements of this immutable parallel range.
Converts this immutable parallel range to a list.
Converts this immutable parallel range to a list.
Note: will not terminate for infinite-sized collections.
a list containing all elements of this immutable parallel range.
[use case] Converts this immutable parallel range to a map.
Converts this immutable parallel range 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.
a map of type immutable.Map[T, U]
containing all key/value pairs of type (T, U) of this immutable parallel range.
Converts this immutable parallel range to a sequence.
Converts this immutable parallel range 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.
a sequence containing all elements of this immutable parallel range.
Converts this immutable parallel range to a set.
Converts this immutable parallel range to a set.
Note: will not terminate for infinite-sized collections.
a set containing all elements of this immutable parallel range.
Converts this immutable parallel range to a stream.
Converts this immutable parallel range to a stream.
Note: will not terminate for infinite-sized collections.
a stream containing all elements of this immutable parallel range.
Creates a String representation of this object.
Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.
a String representation of the object.
Converts this immutable parallel range to an unspecified Traversable.
Converts this immutable parallel range to an unspecified Traversable. Will return the same collection if this instance is already Traversable.
Note: will not terminate for infinite-sized collections.
a Traversable containing all elements of this immutable parallel range.
Converts this immutable parallel range to a Vector.
Converts this immutable parallel range to a Vector.
Note: will not terminate for infinite-sized collections.
a vector containing all elements of this immutable parallel range.
Transposes this immutable parallel range of traversable collections into a immutable parallel range of immutable parallel ranges.
Transposes this immutable parallel range of traversable collections into a immutable parallel range of immutable parallel ranges.
the type of the elements of each traversable collection.
an implicit conversion which asserts that the
element type of this immutable parallel range is a Traversable.
a two-dimensional immutable parallel range of immutable parallel ranges which has as nth row the nth column of this immutable parallel range.
(Changed in version 2.9.0) transpose throws an IllegalArgumentException if collections are not uniformly sized.
if all collections in this immutable parallel range are not of the same size.
[use case] Produces a new sequence which contains all elements of this immutable parallel range and also all elements of a given sequence.
Produces a new sequence which contains all elements of this immutable parallel range and also all elements of
a given sequence. xs union ys is equivalent to xs ++ ys.
Another way to express this
is that xs union ys computes the order-presevring multi-set union of xs and ys.
union is hence a counter-part of diff and intersect which also work on multi-sets.
Note: will not terminate for infinite-sized collections.
the sequence to add.
a new immutable parallel range which contains all elements of this immutable parallel range
followed by all elements of that.
Converts this immutable parallel range of pairs into two collections of the first and second half of each pair.
Converts this immutable parallel range of pairs into two collections of the first and second half of each pair.
the type of the first half of the element pairs
the type of the second half of the element pairs
an implicit conversion which asserts that the element type of this immutable parallel range is a pair.
a pair immutable parallel ranges, containing the first, respectively second half of each element pair of this immutable parallel range.
Converts this immutable parallel range of triples into three collections of the first, second, and third element of each triple.
Converts this immutable parallel range of triples into three collections of the first, second, and third element of each triple.
the type of the first member of the element triples
the type of the second member of the element triples
the type of the third member of the element triples
an implicit conversion which asserts that the element type of this immutable parallel range is a triple.
a triple immutable parallel ranges, containing the first, second, respectively third member of each element triple of this immutable parallel range.
[use case] A copy of this immutable parallel range with one single replaced element.
A copy of this immutable parallel range with one single replaced element.
the position of the replacement
the replacing element
a copy of this immutable parallel range with the element at position index replaced by elem.
[use case] Returns a immutable parallel range formed from this immutable parallel range and another iterable collection by combining corresponding elements in pairs.
Returns a immutable parallel range formed from this immutable parallel range 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.
the type of the second half of the returned pairs
The iterable providing the second half of each result pair
a new immutable parallel range containing pairs consisting of
corresponding elements of this immutable parallel range and that. The length
of the returned collection is the minimum of the lengths of this immutable parallel range and that.
[use case] Returns a immutable parallel range formed from this immutable parallel range and another iterable collection by combining corresponding elements in pairs.
Returns a immutable parallel range formed from this immutable parallel range 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.
the type of the second half of the returned pairs
The iterable providing the second half of each result pair
the element to be used to fill up the result if this immutable parallel range is shorter than that.
the element to be used to fill up the result if that is shorter than this immutable parallel range.
a new immutable parallel range containing pairs consisting of
corresponding elements of this immutable parallel range and that. The length
of the returned collection is the maximum of the lengths of this immutable parallel range and that.
If this immutable parallel range is shorter than that, thisElem values are used to pad the result.
If that is shorter than this immutable parallel range, thatElem values are used to pad the result.
[use case] Zips this immutable parallel range with its indices.
Zips this immutable parallel range with its indices.
Note: might return different results for different runs, unless the underlying collection type is ordered.
A new immutable parallel range containing pairs consisting of all elements of this
immutable parallel range paired with their index. Indices start at 0.
List("a", "b", "c").zipWithIndex = List(("a", 0), ("b", 1), ("c", 2))
(parRange: StringAdd).self
(parRange: StringFormat).self
A syntactic sugar for out of order folding.
A syntactic sugar for out of order folding. See fold.
Example:
scala> val a = LinkedList(1,2,3,4) a: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2, 3, 4) scala> val b = (a /:\ 5)(_+_) b: Int = 15
(Since version 2.10.0) use fold instead
(parRange: ArrowAssoc[ParRange]).x
(Since version 2.10.0) Use leftOfArrow instead
(parRange: Ensuring[ParRange]).x
(Since version 2.10.0) Use resultOfEnsuring instead
Parallel ranges.
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
ParIterableif 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 ofSplitter[T]. Splitters have a methodremainingto check the remaining number of elements, and methodsplitwhich is defined by splitters. Methodsplitdivides 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
tasksupportsetter of the collection.Method
newCombinerproduces a new combiner. Combiners are an extension of builders. They provide a methodcombinewhich 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
parjust returns a reference to this parallel collection. Methodseqis 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,toSeqortoSetalong withparandseqis a flexible way to change between different collection types.Since this trait extends the
GenIterabletrait, methods likesizemust also be implemented in concrete collections, whileiteratorforwards tosplitterby 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.parallelpackage object.Parallel collections are not necessarily ordered in terms of the
foreachoperation (seeTraversable). 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 asforeach,maporfilteralways 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
isStrictSplitterCollectiontofalse. This will make some operations unavailable.To create a new parallel collection, extend the
ParIterabletrait, and implementsize,splitter,newCombinerandseq. Having an implicit combiner factory requires extending this trait in addition, as well as providing a companion object, as with regular collections.Method
sizeis 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.
2.9
Scala's Parallel Collections Library overview section on
ParRangefor more information.