does Iterable does Sequence An RaceSeq is the intermediate object used when race is invoked on a Seq. In general, it's not intended for direct consumption by the developer.
Methods §
method iterator §
method iterator(RaceSeq: --> Iterator)Returns the underlying iterator.
method grep §
method grep(RaceSeq: , *)Applies grep to the RaceSeq similarly to how it would do it on a Seq.
my = (^10000).map(*²).race;.grep( * %% 3 ).say;# OUTPUT: «(0 9 36 81 144 ...)» When you use race on a Seq, this is the method that is actually called.
method map §
method map(RaceSeq: , *)Uses maps on the RaceSeq, generally created by application of .race to a preexisting Seq.
method invert §
method invert(RaceSeq:)Inverts the RaceSeq created from a Seq by .race.
method race §
method race(RaceSeq:)Returns the object.
method hyper §
method hyper(RaceSeq:)Creates a HyperSeq object out of the current one.
method serial §
multi method serial(RaceSeq:)Converts the object to a Seq and returns it.
method is-lazy §
method is-lazy(--> False )Returns False.
method sink §
Defined as:
method sink(--> Nil)Sinks the underlying data structure, producing any side effects.
Type Graph §
RaceSeq
Routines supplied by role Iterable §
RaceSeq does role Iterable, which provides the following routines:
(Iterable) method iterator §
Defined as:
method iterator(--> Iterator)Method stub that ensures all classes doing the Iterable role have a method iterator.
It is supposed to return an Iterator.
say (1..10).iterator;(Iterable) method flat §
Defined as:
method flat(Iterable: --> Iterable)Returns another Iterable that flattens out all iterables that the first one returns.
For example
say (<a b>, 'c').elems; # OUTPUT: «2» say (<a b>, 'c').flat.elems; # OUTPUT: «3»because <a b> is a List and thus iterable, so (<a b>, 'c').flat returns ('a', 'b', 'c'), which has three elems.
Note that the flattening is recursive, so ((("a", "b"), "c"), "d").flat returns ("a", "b", "c", "d"), but it does not flatten itemized sublists:
say ($('a', 'b'), 'c').raku; # OUTPUT: «($("a", "b"), "c")»You can use the hyper method call to call the .List method on all the inner itemized sublists and so de-containerize them, so that flat can flatten them:
say ($('a', 'b'), 'c')>>.List.flat.elems; # OUTPUT: «3»(Iterable) method lazy §
Defined as:
method lazy(--> Iterable)Returns a lazy iterable wrapping the invocant.
say (1 ... 1000).is-lazy; # OUTPUT: «False» say (1 ... 1000).lazy.is-lazy; # OUTPUT: «True»(Iterable) method hyper §
Defined as:
method hyper(Int(Cool) : = 64, Int(Cool) : = 4)Returns another Iterable that is potentially iterated in parallel, with a given batch size and degree of parallelism.
The order of elements is preserved.
say ([1..100].hyper.map().list);Use hyper in situations where it is OK to do the processing of items in parallel, and the output order should be kept relative to the input order. See race for situations where items are processed in parallel and the output order does not matter.
Options degree and batch §
The degree option (short for "degree of parallelism") configures how many parallel workers should be started. To start 4 workers (e.g. to use at most 4 cores), pass :4degree to the hyper or race method. Note that in some cases, choosing a degree higher than the available CPU cores can make sense, for example I/O bound work or latency-heavy tasks like web crawling. For CPU-bound work, however, it makes no sense to pick a number higher than the CPU core count.
The batch size option configures the number of items sent to a given parallel worker at once. It allows for making a throughput/latency trade-off. If, for example, an operation is long-running per item, and you need the first results as soon as possible, set it to 1. That means every parallel worker gets 1 item to process at a time, and reports the result as soon as possible. In consequence, the overhead for inter-thread communication is maximized. In the other extreme, if you have 1000 items to process and 10 workers, and you give every worker a batch of 100 items, you will incur minimal overhead for dispatching the items, but you will only get the first results when 100 items are processed by the fastest worker (or, for hyper, when the worker getting the first batch returns.) Also, if not all items take the same amount of time to process, you might run into the situation where some workers are already done and sit around without being able to help with the remaining work. In situations where not all items take the same time to process, and you don't want too much inter-thread communication overhead, picking a number somewhere in the middle makes sense. Your aim might be to keep all workers about evenly busy to make best use of the resources available.
You can also check out this blog post on the semantics of hyper and race
(Iterable) method race §
Defined as:
method race(Int(Cool) : = 64, Int(Cool) : = 4 --> Iterable)Returns another Iterable that is potentially iterated in parallel, with a given batch size and degree of parallelism (number of parallel workers).
Unlike hyper, race does not preserve the order of elements (mnemonic: in a race, you never know who will arrive first).
say ([1..100].race.map().list);Use race in situations where it is OK to do the processing of items in parallel, and the output order does not matter. See hyper for situations where you want items processed in parallel and the output order should be kept relative to the input order.
Blog post on the semantics of hyper and race
See hyper for an explanation of :$batch and :$degree.
Routines supplied by role Sequence §
RaceSeq does role Sequence, which provides the following routines:
(Sequence) method Str §
multi method Str(::?CLASS:)Stringifies the cached sequence.
(Sequence) method Stringy §
multi method Stringy(::?CLASS:)Calls .Stringy on the cached sequence.
(Sequence) method Numeric §
method Numeric(::?CLASS:)Returns the number of elements in the cached sequence.
(Sequence) method AT-POS §
multi method AT-POS(::?CLASS: Int )multi method AT-POS(::?CLASS: int )Returns the element at position $idx in the cached sequence.
(Sequence) method EXISTS-POS §
multi method EXISTS-POS(::?CLASS: Int )multi method EXISTS-POS(::?CLASS: int )Returns a Bool indicating whether there is an element at position $idx in the cached sequence.
(Sequence) method eager §
method eager(::?CLASS: --> List)Returns an eagerly evaluated List based on the invocant sequence, and marks it as consumed. If called on an already consumed Seq, throws an error of type X::Seq::Consumed.
my = lazy 1..5; say .is-lazy; # OUTPUT: «True» say .eager; # OUTPUT: «(1 2 3 4 5)» say .eager;CATCH # OUTPUT: «Throws exception if already consumed»(Sequence) method fmt §
method fmt( = '%s', = ' ' --> Str)(Sequence) method gist §
multi method gist(::?CLASS:)Returns the gist of the cached sequence.
Routines supplied by role PositionalBindFailover §
RaceSeq does role PositionalBindFailover, which provides the following routines:
(PositionalBindFailover) method cache §
method cache(PositionalBindFailover: --> List)Returns a List based on the iterator method, and caches it. Subsequent calls to cache always return the same List object.
(PositionalBindFailover) method list §
multi method list(::?CLASS:)Returns a List based on the iterator method without caching it.
(PositionalBindFailover) method iterator §
method iterator(PositionalBindFailover:) This method stub ensure that a class implementing role PositionalBindFailover provides an iterator method.