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Last data update: 2014.03.03

R: Consumer class to combine successive records

Reducer

R Documentation

Consumer class to combine successive records

Description

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

Usage

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

Arguments

`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.

Methods

See Consumer Methods.

Internal Class Fields and 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().

Author(s)

Martin Morgan mtmorgan@fhcrc.org

Examples

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
}

Results


R version 3.3.1 (2016-06-21) -- "Bug in Your Hair"
Copyright (C) 2016 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)

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Type 'demo()' for some demos, 'help()' for on-line help, or
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Type 'q()' to quit R.

> library(Streamer)
> png(filename="/home/ddbj/snapshot/RGM3/R_BC/result/Streamer/Reducer-class.Rd_%03d_medium.png", width=480, height=480)
> ### Name: Reducer
> ### Title: Consumer class to combine successive records
> ### Aliases: Reducer Reducer-class
> ### Keywords: classes
> 
> ### ** Examples
> 
> s <- Stream(Seq(to=10), Reducer("+"))
> yield(s)     ## sum(1:10), i.e., Reduce over the entire stream
[1] 55
> s <- Stream(Seq(to=10), Reducer("+", yieldNth=5))
> yield(s)     ## sum(1:5)
[1] 15
> yield(s)     ## sum(6:10)
[1] 40
> s <- Stream(Seq(to=10), Reducer("+", init=10, yieldNth=5))
> sapply(s, c) ## 10 + c(sum(1:5), sum(6:10))
[1] 25 50
> 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
+ }
[1] 55
> 
> 
> 
> 
> 
> 
> dev.off()
null device 
          1 
>