Running R code in parallel on Heroku

init.r

# used by the R buildpack to install dependencies:
# https://github.com/virtualstaticvoid/heroku-buildpack-r
install.packages("foreach", dependencies = TRUE)
install.packages("doParallel", dependencies = TRUE)

output.txt

$ heroku run bash
Running `bash` attached to terminal... up, run.5154

~ $ Rscript testSequential.r 
[1] "Hello"
Loading required package: iterators
Loading required package: parallel
elapsed 
 57.408 

~ $ Rscript testParallel.r 
[1] "Hello"
Loading required package: iterators
Loading required package: parallel
elapsed 
 33.467 

parallel.r

# example from: http://cran.r-project.org/web/packages/doParallel/vignettes/gettingstartedParallel.pdf
library(foreach)
library(doParallel)
registerDoParallel(cores=2)

x <- iris[which(iris[,5] != "setosa"), c(1,5)]
trials <- 10000
ptime <- system.time({
	r <- foreach(icount(trials), .combine=cbind) %dopar% {
		 ind <- sample(100, 100, replace=TRUE)
		result1 <- glm(x[ind,2]~x[ind,1], family=binomial(logit))
		coefficients(result1)
	}
})[3]
print(ptime)

sequential.r

# example from: http://cran.r-project.org/web/packages/doParallel/vignettes/gettingstartedParallel.pdf
library(foreach)
library(doParallel)
registerDoParallel(cores=2)

x <- iris[which(iris[,5] != "setosa"), c(1,5)]
trials <- 10000
ptime <- system.time({
	r <- foreach(icount(trials), .combine=cbind) %do% { # note the only difference here is using %do% instead of %dopar%
		 ind <- sample(100, 100, replace=TRUE)
		result1 <- glm(x[ind,2]~x[ind,1], family=binomial(logit))
		coefficients(result1)
	}
})[3]
print(ptime)