R devel - May 2014 - mcmapply Core Usage

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

Dario,

yes, that is a bug, now fixed.

Cheers,
Simon


On May 29, 2014, at 2:00 AM, Dario Strbenac <dstr7320 at
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
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>