Reducer-class: Consumer class to combine successive records
In Streamer: Enabling stream processing of large files

Description Usage Arguments Methods Internal Class Fields and Methods Author(s) See Also Examples

A Consumer-class to reduce N successive records into a single yield.

1	Reducer(FUN, init, ..., yieldNth = NA_integer_)

`FUN`	A function of two arguments, where the first argument is the result of the previous reduction (or `init`, if specified, for the first record) and the second argument is the current record.
`init`	An optional initial value to initiate the reduction. When present, `init` is used to initial each yield.
`...`	Additional arguments, passed to the `$new` method of the underlying reference class. Currently unused.
`yieldNth`	A positive integer indicating how many upstream yields are combined before the Reducer yields. A value of `NA_integer_` indicates reduction of all records in the input stream.

See Consumer Methods.

Internal fields of this class are are described with, e.g., getRefClass("Reducer")$fields.

Internal methods of this class are described with getRefClass("Reducer")$methods() and getRefClass("Reducer")$help().

Martin Morgan mtmorgan@fhcrc.org

Stream

s <- Stream(Seq(to=10), Reducer("+"))
yield(s)     ## sum(1:10), i.e., Reduce over the entire stream
s <- Stream(Seq(to=10), Reducer("+", yieldNth=5))
yield(s)     ## sum(1:5)
yield(s)     ## sum(6:10)
s <- Stream(Seq(to=10), Reducer("+", init=10, yieldNth=5))
sapply(s, c) ## 10 + c(sum(1:5), sum(6:10))
if (.Platform$OS.type != "windows") {
    s <- Stream(Seq(to=10),
                Team(function(i) { Sys.sleep(1); i },
                     param=MulticoreParam(10L)),
                Reducer("+"))
    system.time(y <- yield(s))
    y
}