dear R experts---
I am experimenting with multicore processing, so far with pretty
disappointing results. Here is my simple example:
A <- 100000
randvalues <- abs(rnorm(A))
minfn <- function( x, i ) { log(abs(x))+x^3+i/A+randvalues[i] } ## an
arbitrary function
ARGV <- commandArgs(trailingOnly=TRUE)
if (ARGV[1] == "do-onecore") {
library(foreach)
discard <- foreach(i = 1:A) %do% uniroot( minfn, c(1e-20,9e20), i ) } else
if (ARGV[1] == "do-multicore") {
library(doMC)
registerDoMC()
cat("You have", getDoParWorkers(), "cores\n")
discard <- foreach(i = 1:A) %dopar% uniroot( minfn, c(1e-20,9e20), i ) } else
if (ARGV[1] == "plain")
for (i in 1:A) discard <- uniroot( minfn, c(1e-20,9e20), i ) else
cat("sorry, but argument", ARGV[1], "is not plain|do-onecore|do-multicore\n")
on my Mac Pro 3,1 (2 quad-cores), R 2.12.0, which reports 8 cores,
"plain" takes about 68 seconds (real and user, using the unix timing
function).
"do-onecore" takes about 300 seconds.
"do-multicore" takes about 210 seconds real, (300 seconds user).
this seems pretty disappointing. the cores are not used for the most
part, either. feedback appreciated.
/iaw
----
Ivo Welch (ivo.we...@gmail.com)
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