R语言中for，snow，foreach时间比较

代码记录

library(RMySQL)library(nnet)library(plyr)library(lattice)library(e1071)library(foreach)library(doParallel)#read info from sqlsql_data<-"select distinct(MP_ID) from DataPower"conn<-dbConnect(MySQL(),user="",password="",dbname="powerloaddata",host="")  #开启数据库连接data_info<-dbGetQuery(conn,sql_data)   #获得原始数据   611363856dbDisconnect(conn)  #关闭数据库连接mp_id = as.numeric(data_info[,1])# 启用parallel作为foreach并行计算的后端cl <- makeCluster(20)registerDoParallel(cl)rm(meanDataForeach)foreach (x=1:length(mp_id))  %dopar% {trainAndtest(mp_id[x])}

关于foreach的效率问题

看了stackoverflow
发现foreach在多循环的情况下效率不高。
原话是：
foreach is only advisable if you have relatively few rounds through very time consuming functions.