怎么在R语言中使用for循环实现并行处理?很多新手对此不是很清楚,为了帮助大家解决这个难题,下面小编将为大家详细讲解,有这方面需求的人可以来学习下,希望你能有所收获。什么是R语言R语言是用于统计分析、绘图的语言和操作环境,属于GNU系统的一
怎么在R语言中使用for循环实现并行处理?很多新手对此不是很清楚,为了帮助大家解决这个难题,下面小编将为大家详细讲解,有这方面需求的人可以来学习下,希望你能有所收获。
R语言是用于统计分析、绘图的语言和操作环境,属于GNU系统的一个自由、免费、源代码开放的软件,它是一个用于统计计算和统计制图的优秀工具。
func <- function(x, y, z) { return(x^y/z)}# >>> main <<<x <- 2y <- 3z <- 1:100000start <- (proc.time())[3][[1]]a <- 0for (i_z in z) { a <- a + func(x, y, i_z)}end <- (proc.time())[3][[1]]print(paste('Result = ', round(a, 2), ', time = ', (end-start), 's', sep=''))
输出:
[1] "Result = 96.72, time = 0.177s"
library(foreach)library(doParallel)func <- function(x, y, z) { return(x^y/z)}# >>> main <<<x <- 2y <- 3z <- 1:100000start <- (proc.time())[3][[1]]cl <- makeCluster(12)reGISterDoParallel(cl)a <- foreach(z=z, .combine='rbind') %dopar% func(x, y, z)a <- sum(a)stopCluster(cl)end <- (proc.time())[3][[1]]print(paste('Result = ', round(a, 2), ', time = ', (end-start), 's', sep=''))
输出:
[1] "Result = 96.72, time = 37.988s"
这里发现并行化所用时间大于非并行化所用过的时间,是因为需要执行的操作(func函数)过于简单,而foreach处理时会有额外的资源消耗。此时foreach额外消耗的资源远大于需要执行的操作所需的资源,因此会导致并行化后反而使用的时间增加了。所以对于一些复杂的操作比较适合使用并行化的策略。
foreach函数的.packages参数可以为并行化函数传递额外需要的包。
foreach中的参数为需要在func中循环的变量,其他固定的变量则在func中传入。参数可以是data.frame类型。
补充:R语言--for循环语句的使用
对于多个for循还语句,R语言的执行顺序(以3个for为例):从外向内单个执行,里边循还完整,再往外一层,直到全部完成。话不多说,上例子:
代码:
library(data.table)mm<-data.table()m<-c(1,2,3,4,5)n<-c('a','b','c','d','e')o<-c(6,7,8,9,10)for (i1 in m){ for ( i2 in n){ for (i3 in o){ print(c(i1,i2,i3)) aa<-data.table(i1,i2,i3) bb<-rbind(mm,aa) } }}
执行结果:
[1] "1" "a" "6"[1] "1" "a" "7"[1] "1" "a" "8"[1] "1" "a" "9"[1] "1" "a" "10"[1] "1" "b" "6"[1] "1" "b" "7"[1] "1" "b" "8"[1] "1" "b" "9"[1] "1" "b" "10"[1] "1" "c" "6"[1] "1" "c" "7"[1] "1" "c" "8"[1] "1" "c" "9"[1] "1" "c" "10"[1] "1" "d" "6"[1] "1" "d" "7"[1] "1" "d" "8"[1] "1" "d" "9"[1] "1" "d" "10"[1] "1" "e" "6"[1] "1" "e" "7"[1] "1" "e" "8"[1] "1" "e" "9"[1] "1" "e" "10"[1] "2" "a" "6"[1] "2" "a" "7"[1] "2" "a" "8"[1] "2" "a" "9"[1] "2" "a" "10"[1] "2" "b" "6"[1] "2" "b" "7"[1] "2" "b" "8"[1] "2" "b" "9"[1] "2" "b" "10"[1] "2" "c" "6"[1] "2" "c" "7"[1] "2" "c" "8"[1] "2" "c" "9"[1] "2" "c" "10"[1] "2" "d" "6"[1] "2" "d" "7"[1] "2" "d" "8"[1] "2" "d" "9"[1] "2" "d" "10"[1] "2" "e" "6"[1] "2" "e" "7"[1] "2" "e" "8"[1] "2" "e" "9"[1] "2" "e" "10"[1] "3" "a" "6"[1] "3" "a" "7"[1] "3" "a" "8"[1] "3" "a" "9"[1] "3" "a" "10"[1] "3" "b" "6"[1] "3" "b" "7"[1] "3" "b" "8"[1] "3" "b" "9"[1] "3" "b" "10"[1] "3" "c" "6"[1] "3" "c" "7"[1] "3" "c" "8"[1] "3" "c" "9"[1] "3" "c" "10"[1] "3" "d" "6"[1] "3" "d" "7"[1] "3" "d" "8"[1] "3" "d" "9"[1] "3" "d" "10"[1] "3" "e" "6"[1] "3" "e" "7"[1] "3" "e" "8"[1] "3" "e" "9"[1] "3" "e" "10"[1] "4" "a" "6"[1] "4" "a" "7"[1] "4" "a" "8"[1] "4" "a" "9"[1] "4" "a" "10"[1] "4" "b" "6"[1] "4" "b" "7"[1] "4" "b" "8"[1] "4" "b" "9"[1] "4" "b" "10"[1] "4" "c" "6"[1] "4" "c" "7"[1] "4" "c" "8"[1] "4" "c" "9"[1] "4" "c" "10"[1] "4" "d" "6"[1] "4" "d" "7"[1] "4" "d" "8"[1] "4" "d" "9"[1] "4" "d" "10"[1] "4" "e" "6"[1] "4" "e" "7"[1] "4" "e" "8"[1] "4" "e" "9"[1] "4" "e" "10"[1] "5" "a" "6"[1] "5" "a" "7"[1] "5" "a" "8"[1] "5" "a" "9"[1] "5" "a" "10"[1] "5" "b" "6"[1] "5" "b" "7"[1] "5" "b" "8"[1] "5" "b" "9"[1] "5" "b" "10"[1] "5" "c" "6"[1] "5" "c" "7"[1] "5" "c" "8"[1] "5" "c" "9"[1] "5" "c" "10"[1] "5" "d" "6"[1] "5" "d" "7"[1] "5" "d" "8"[1] "5" "d" "9"[1] "5" "d" "10"[1] "5" "e" "6"[1] "5" "e" "7"[1] "5" "e" "8"[1] "5" "e" "9"[1] "5" "e" "10"
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