[Rd] problem using rJava with parallel::mclapply

[Cook, Malcolm]

Karl,

I have the following notes to self that may be pertinent:

options(java.parameters=
         ## Must preceed `library(XLConnect)` in order to prevent "Java
         ## requested System.exit(130), closing R." which happens when
         ## rJava quits R upon trapping INT (control-c), as is done by
         ## XLConnect (and playwith?), below. (c.f.:
         ## https://www.rforge.net/bugzilla/show_bug.cgi?id=237)
         "-Xrs")


~Malcolm



 >-----Original Message-----
 >From: r-devel-bounces at r-project.org [mailto:r-devel-bounces at r-project.org] On Behalf Of Karl Forner
 >Sent: Monday, November 11, 2013 11:41 AM
 >To: r-devel at r-project.org
 >Cc: Martin Studer
 >Subject: [Rd] problem using rJava with parallel::mclapply
 >
 >Dear all,
 >
 >I got an issue trying to parse excel files in parallel using XLConnect, the
 >process hangs forever.
 >Martin Studer, the maintainer of XLConnect kindly investigated the issue,
 >identified rJava as a possible cause of the problem:
 >
 >This does not work (hangs):
 >library(parallel)
 >require(rJava)
 >.jinit()
 >res <- mclapply(1:2, function(i) {
 >      J("java.lang.Runtime")$getRuntime()$gc()
 >      1
 >  }, mc.cores = 2)
 >
 >but this works:
 >library(parallel)
 >res <- mclapply(1:2, function(i) {
 >  require(rJava)
 >  .jinit()
 >  J("java.lang.Runtime")$getRuntime()$gc()
 >  1
 >}, mc.cores = 2)
 >
 >To cite Martin, it seems to work with mclapply when the JVM process is
 >initialized after forking.
 >
 >Is this a bug or a limitation of rJava ?
 >Or is there a good practice for rJava clients to avoid this problem ?
 >
 >Best,
 >Karl
 >
 >P.S.
 >> sessionInfo()
 >R version 3.0.1 (2013-05-16)
 >Platform: x86_64-unknown-linux-gnu (64-bit)
 >
 >locale:
 > [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 > [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 > [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
 > [7] LC_PAPER=C                 LC_NAME=C
 > [9] LC_ADDRESS=C               LC_TELEPHONE=C
 >[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
 >
 >attached base packages:
 >[1] stats     graphics  grDevices utils     datasets  methods   base
 >
 >loaded via a namespace (and not attached):
 >[1] tools_3.0.1
 >
 >	[[alternative HTML version deleted]]
 >
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