為什么我的 R 代碼在使用 foreach 時不是並行 CPU

Question

我的代碼很長，所以我用“foreach”將它們包裝到並行多 CPU。 但看起來只有 1 個 CPU 核心在忙着運行。

這是我的代碼：

library(doParallel)  
library(foreach)
no_cores <- detectCores() - 2             # leave 2 core2 for the system
registerDoParallel(cores = no_cores)  

ReadList <- read_excel("E:xxxx")
foreach(Index = 1:nrow(ReadList)) %do% { 
 # code body part is huge
 write.table(D.results, quote = FALSE, sep = " ", paste(outputpath, "Daily_", List$Gid[Index], ".txt", sep=""))   # I output result for each Index within the loop
}

Answer 1

就像@coletl 所說，如果您希望 foreach 並行運行，您需要將%do%更改為%dopar% 。

library(doParallel)  
library(foreach)
no_cores <- detectCores() - 2             # leave 2 core2 for the system
registerDoParallel(cores = no_cores)  

ReadList <- read_excel("E:xxxx")
foreach(Index = 1:nrow(ReadList)) %dopar% { 
 # code body part is huge
 write.table(D.results, quote = FALSE, sep = " ", paste(outputpath, "Daily_", List$Gid[Index], ".txt", sep=""))   # I output result for each Index within the loop
}