[Rd] parallel::mclapply does not return try-error objects with mc.preschedule=TRUE

[Karl Forner]

Hello,

Consider this:

1)
library(parallel)
res <- mclapply(1:2, stop)
#Warning message:
#In mclapply(1:2, stop) :
# all scheduled cores encountered errors in user code

is(res[[1]], 'try-error')
#[1] FALSE


2)
library(parallel)
res <- mclapply(1:2, stop, mc.preschedule=FALSE)
#Warning message:
#In mclapply(1:2, stop, mc.preschedule = FALSE) :
#  2 function calls resulted in an error

is(res[[1]], 'try-error')
#[1] TRUE

The documentation states that:
'Each forked process runs its job inside try(..., silent = TRUE) so if
errors occur they will be stored as class "try-error" objects in the
return value and a warning will be given.'


Is this a bug ?

Thanks
Karl


> sessionInfo()
R version 2.15.3 (2013-03-01)
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] parallel  stats     graphics  grDevices utils     datasets  methods
[8] base

loaded via a namespace (and not attached):
[1] tools_2.15.3