为什么我的 R 代码在使用 foreach 时不并行 CPU

Question

我的代码很长，所以我用“foreach”将它们包装成并行多CPU。但看起来只有 1 CPU 个核心忙 运行。

这是我的代码：

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 说的，如果你想让foreach 与运行 并行，你需要将%do% 更改为%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
}