Loop Time Test

Output.txt

R version 3.3.3 (2017-03-06) -- "Another Canoe"
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> system.time(rm(list=ls()))
   user  system elapsed 
      0       0       0 
> system.time(a <- seq(1, 10000, 0.5))
   user  system elapsed 
      0       0       0 
> system.time(
+   for(i in 1:length(a)) {
+     b <- ifelse((a %/% 1)==1, T, F)
+   }
+ )
   user  system elapsed 
  22.12    0.00   22.14 
> library(foreach)
foreach: simple, scalable parallel programming from Revolution Analytics
Use Revolution R for scalability, fault tolerance and more.
http://www.revolutionanalytics.com
> system.time(
+   foreach(a) %do%
+     (
+       c <- ifelse((a %/% 1)==1, T, F)
+     )
+ )
   user  system elapsed 
  20.01    0.15   20.17 
> system.time(
+   foreach(a) %dopar%
+     (
+       d <- ifelse((a %/% 1)==1, T, F)
+     )
+ )
   user  system elapsed 
  19.44    0.00   19.43 
Warning message:
executing %dopar% sequentially: no parallel backend registered 
> library("doParallel")
Loading required package: iterators
Loading required package: parallel
> cl <- makePSOCKcluster(12)
> registerDoParallel(cl)
> system.time(
+   foreach(a) %dopar%
+     (
+       e <- ifelse((a %/% 1)==1, T, F)
+     )
+ )
   user  system elapsed 
   7.75    3.43   11.49 
> stopCluster(cl)
> rm(cl)
> library(doSNOW)
Loading required package: snow

Attaching package: ‘snow’

The following objects are masked from ‘package:parallel’:

    clusterApply, clusterApplyLB, clusterCall, clusterEvalQ, clusterExport, clusterMap, clusterSplit, makeCluster, parApply, parCapply, parLapply, parRapply, parSapply, splitIndices, stopCluster

> cl <- makeCluster(12, type="SOCK")
> system.time(
+   foreach(a) %dopar%
+     (
+       f <- ifelse((a %/% 1)==1, T, F)
+     )
+ )
   user  system elapsed 
   7.66    3.62   11.64 
> stopCluster(cl)
> rm(cl)
> 

Script.R

system.time(rm(list=ls()))
system.time(a <- seq(1, 10000, 0.5))
system.time(
  for(i in 1:length(a)) {
    b <- ifelse((a %/% 1)==1, T, F)
  }
)
library(foreach)
system.time(
  foreach(a) %do%
    (
      c <- ifelse((a %/% 1)==1, T, F)
    )
)
system.time(
  foreach(a) %dopar%
    (
      d <- ifelse((a %/% 1)==1, T, F)
    )
)
library("doParallel")
cl <- makePSOCKcluster(12)
registerDoParallel(cl)
system.time(
  foreach(a) %dopar%
    (
      e <- ifelse((a %/% 1)==1, T, F)
    )
)
stopCluster(cl)
rm(cl)
library(doSNOW)
cl <- makeCluster(12, type="SOCK")
system.time(
  foreach(a) %dopar%
    (
      f <- ifelse((a %/% 1)==1, T, F)
    )
)
stopCluster(cl)
rm(cl)