[R-sig-hpc] Warning "closing unused connection..." with package parallel

[Zepu Zhang]

Thanks for the response. Olaf pointed out my second 'on.exit'
overwrote the first 'on.exit'; that fixed the problem.

Zepu

On Sun, Jan 22, 2012 at 5:14 PM, Dirk Eddelbuettel <edd at debian.org> wrote:
>
> On 22 January 2012 at 15:33, Zepu Zhang wrote:
> | Dear list,
> |
> | After running the following chunk of code repeatedly in a package
> |
> | library(parellel)
> |
> | f <- function(nsim, ...)
> | {
> |         cl <- makeCluster(detectCores())
> |         on.exit(stopCluster(cl))
> |         rng.kind <- RNGkind()
> |         on.exit(RNGkind(rng.kind[1], rng.kind[2]))
> |         RNGkind("L'Ecuyer-CMRG")
> |         clusterSetRNGStream(cl, trunc(runif(1) * 10000))
> |
> |         z <- clusterApply(cl, seq_len(nsim),
> |                 function(dummy, ...)
> |                    { #some custom function that does simulation
> |                    },
> |                 # additional arguments passed into function
> |                 )
> |       # other stuff
> | }
> |
> | I got > 50 warnings like
> |
> | 34: closing unused connection 3 (<-localhost.localdomain:10187)
> | 35: closing unused connection 4 (<-localhost.localdomain:10187)
> | 36: closing unused connection 3 (<-localhost.localdomain:10187)
> | 37: closing unused connection 4 (<-localhost.localdomain:10187)
> | 38: closing unused connection 3 (<-localhost.localdomain:10187)
> |
> | I've tested this on two Linux boxes with detectCores() returning 2 and
> | 4, respectively, getting the same type of warnings. Although 2 and 4
> | cores seem to be few, I need this parallel capabilities so that it's
> | beneficial when the code is run on machines with more cores. It will
> | be run on both Linux and Windows.
> |
> | The function called by 'clusterApply' calls package 'RandomFields' for
> | simulations. It is not apparent that 'RandomFields' does parallel
> | computations (which might interfere with R).
> |
> | Any idea what caused these warning messages? If they are harmless, I
> | really want to avoid them b/c they can mask other useful warnings.
>
> Try calling stopCluster(cl) when you're done. The documentation, accessible
> via help(makeCluster,package="parallel") states this:
>
>     It is good practice to shut down the workers by calling
>     ‘stopCluster’: however the workers will terminate themselves once
>     the socket on which they are listening for commands becomes
>     unavailable, which it should if the master R session is completed
>     (or its process dies).
>
> Dirk
>
> |
> | Thanks!
> |
> | Zepu Zhang
> |
> | _______________________________________________
> | R-sig-hpc mailing list
> | R-sig-hpc at r-project.org
> | https://stat.ethz.ch/mailman/listinfo/r-sig-hpc
>
> --
> "Outside of a dog, a book is a man's best friend. Inside of a dog, it is too
> dark to read." -- Groucho Marx