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package scala.collection.parallel
import scala.collection.Seq
/** A splitter (or a split iterator) can be split into more splitters that traverse over
* disjoint subsets of elements.
*
* @tparam T type of the elements this parallel iterator traverses
*
* @since 2.8.1
* @author prokopec
*/
trait Splitter[+T] extends Iterator[T] {
/** Splits the iterator into a sequence of disjunct views.
*
* Returns a sequence of split iterators, each iterating over some subset of the
* elements in the collection. These subsets are disjoint and should be approximately
* equal in size. These subsets are not empty, unless the iterator is empty in which
* case this method returns a sequence with a single empty iterator. If the iterator has
* more than two elements, this method will return two or more iterators.
*
* Implementors are advised to keep this partition relatively small - two iterators are
* already enough when partitioning the collection, although there may be a few more.
*
* '''Note:''' this method actually invalidates the current iterator.
*
* @return a sequence of disjunct iterators of the collection
*/
def split: Seq[Splitter[T]]
}
/** A precise splitter (or a precise split iterator) can be split into arbitrary number of splitters
* that traverse disjoint subsets of arbitrary sizes.
*
* Implementors might want to override the parameterless `split` method for efficiency.
*
* @tparam T type of the elements this parallel iterator traverses
*
* @since 2.8.1
* @author prokopec
*/
trait PreciseSplitter[+T] extends Splitter[T] {
/** Splits the iterator into disjunct views.
*
* This overloaded version of the `split` method is specific to precise parallel iterators.
* It returns a sequence of parallel iterators, each iterating some subset of the
* elements in this iterator. The sizes of the subiterators in the partition is equal to
* the size in the corresponding argument, as long as there are enough elements in this
* iterator to split it that way.
*
* If there aren't enough elements, a zero element iterator is appended for each additional argument.
* If there are additional elements, an additional iterator is appended at the end to compensate.
*
* For example, say we have a parallel iterator `ps` with 100 elements. Invoking:
* {{{
* ps.split(50, 25, 25, 10, 5)
* }}}
* will return a sequence of five iterators, last two views being empty. On the other hand, calling:
* {{{
* ps.split(50, 40)
* }}}
* will return a sequence of three iterators, last of them containing ten elements.
*
* '''Note:''' this method actually invalidates the current iterator.
*
* Unlike the case with `split` found in parallel iterable iterators, views returned by this method can be empty.
*
* @param sizes the sizes used to split this split iterator into iterators that traverse disjunct subsets
* @return a sequence of disjunct subsequence iterators of this parallel iterator
*/
def psplit(sizes: Int*): Seq[PreciseSplitter[T]]
def split: Seq[PreciseSplitter[T]]
}
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