Simon Urbanek skrev 2014-05-29 15:06:
Dario,

yes, that is a bug, now fixed.

Thanks for fixing it.

This problem was independently reported some time ago (https://bugs.r-project.org/bugzilla/show_bug.cgi?id=15016) and I believe that it can now be closed.

Henric



Cheers,
Simon


On May 29, 2014, at 2:00 AM, Dario Strbenac <dstr7...@uni.sydney.edu.au> wrote:

Hello,

I have a minimal example that shows a problem I'm having with parallel 
processing.

library(parallel)
mcmapply(function(x, y)
{
  print("Running")
  Sys.sleep(10)
}, as.list(1:10), as.list(10:1), mc.cores = 16, SIMPLIFY = FALSE)

I see "Running" printed once every ten seconds. I read the documentation for 
mcmapply, but I don't understand why it wouldn't print all ten output statements almost 
at once, then wait for about ten seconds, then return to the prompt. Is it documented in 
another location ?

My problem is that I have a section of code that takes a long time, which I 
have replaced with Sys.sleep in the above example, but when I look at the 
output of top, I only see 1 CPU being used. The computer has 16 processors.

sessionInfo()
R version 3.1.0 (2014-04-10)
Platform: x86_64-pc-linux-gnu (64-bit)

locale:
[1] LC_CTYPE=en_AU.UTF-8       LC_NUMERIC=C
[3] LC_TIME=en_AU.UTF-8        LC_COLLATE=en_AU.UTF-8
[5] LC_MONETARY=en_AU.UTF-8    LC_MESSAGES=en_AU.UTF-8
[7] LC_PAPER=en_AU.UTF-8       LC_NAME=C
[9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_AU.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] parallel  stats     graphics  grDevices utils     datasets  methods
[8] base

loaded via a namespace (and not attached):
[1] tools_3.1.0

--------------------------------------
Dario Strbenac
PhD Student
University of Sydney
Camperdown NSW 2050
Australia

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