我最近得到了一台具有多个核心的计算机,并且正在学习使用并行计算。我相当熟练lapply
并被告知parLapply
工作原理非常相似。但我没有正确操作它。看来我必须明确地将所有内容放入parLapply
使其工作(即要使用的函数、变量等)。和lapply
它从父环境中读取并且parLapply
似乎没有这样做。因此,在下面的示例中,我可以通过将所有信息放入其中来使一切正常工作parLapply
但如果我在用户定义的函数中使用它,我无法显式地放置text.var
代替parLapply
.
library(parallel)
text.var <- rep("I like cake and ice cream so much!", 20)
ntv <- length(text.var)
gc.rate <- 10
pos <- function(i) {
paste(sapply(strsplit(tolower(i), " "), nchar), collapse=" | ")
}
lapply(seq_len(ntv), function(i) {
x <- pos(text.var[i])
if (i%%gc.rate==0) gc()
return(x)
}
)
#doesn't work
cl <- makeCluster(mc <- getOption("cl.cores", 4))
parLapply(cl, seq_len(ntv), function(i) {
x <- pos(text.var[i])
if (i%%gc.rate==0) gc()
return(x)
}
)
#does work but have to specify all the stuff inside parLapply
cl <- makeCluster(mc <- getOption("cl.cores", 4))
parLapply(cl, seq_len(ntv), function(i) {
######stuff I have to put inside parLapply##########
text.var <- rep("I like cake and ice cream so much!", 20)
ntv <- length(text.var)
gc.rate <- 10
pos <- function(i) {
paste(sapply(strsplit(tolower(i), " "), nchar), collapse=" | ")
}
######stuff I have to put inside parLapply##########
x <- pos(text.var[i])
if (i%%gc.rate==0) gc()
return(x)
}
)
我怎样才能通过text.var
, ntv
, gc.rate
, and pos
to parLapply
没有明确地将它们放入其中? (我猜你以某种方式将它们作为列表传递)
PS windows 7机器所以我需要使用parLapply
I think