library('microbenchmark')
library('Rcpp')
library('RcppParallel')
library('foreach')
library('doParallel')
library('iterators')

sourceCpp('testrcpp.cpp')

##~~~~~~~~~~~~~~~~~~~R parallel~~~~~~~~~~~~~~~~~
SqrtRPara <- function(orig, n = 8) {

  registerDoParallel(cores = n)

  itx <- iter(orig)

  res <- foreach(i = itx, .combine = c) %dopar% {
    return(sqrt(i))
  }

  ## stop multiple cores
  stopImplicitCluster()

  return(res)
}

SqrtR <- function(orig) {

  res <- numeric(length(orig))

  for (i in orig) {
    res[i] <- sqrt(orig[i])
  }

  return(res)

}
##~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

##~~~~~~~~~~~~~~~~test~~~~~~~~~~~~~~~~~~~~~
tmp1 <- runif(10e3)

all.equal(SqrtCpp(tmp1),
          sqrt(tmp1),
          SqrtCppPara(tmp1))

microbenchmark(
  SqrtCpp(tmp1),
  sqrt(tmp1),
  SqrtCppPara(tmp1)
)

all.equal(SqrtCpp(tmp1),
          sqrt(tmp1),
          SqrtR(tmp1),
          SqrtRPara(tmp1),
          SqrtCppPara(tmp1))

microbenchmark(
  SqrtCpp(tmp1),
  sqrt(tmp1),
  SqrtRPara(tmp1),
  SqrtR(tmp1),
  SqrtCppPara(tmp1)
)
##~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~