[Rd] clusterApply arguments

[Henrik Bengtsson]

This is nothing specific to parallel::clusterApply() per se. It is the
default behavior of R where it allows for partial argument names.  I
don't think there's much that can be done here except always using
fully named arguments to the "apply" function itself as you show.

You can "alert" yourself when there's a mistake by using:

options(warnPartialMatchArgs = TRUE)

e.g.

> clusterApply(clu, x = 1:2, fun = fun, c = 1) ## Error
Warning in clusterApply(clu, x = 1:2, fun = fun, c = 1) :
  partial argument match of 'c' to 'cl'
Error in checkCluster(cl) : not a valid cluster

It's still only a warning, but an informative one.

/Henrik

On Wed, Mar 14, 2018 at 8:50 AM, Florian Schwendinger
<Florian_Schwendinger at gmx.at> wrote:
> Hi!
>
> I recognized that the argument matching of clusterApply (and therefore parLapply) goes wrong when one of the arguments of the function is called "c". In this case, the argument "c" is used as cluster and the functions give the following error message "Error in checkCluster(cl) : not a valid cluster".
>
> Of course, "c" is for many reasons an unfortunate argument name and this can be easily fixed by the user side.
>
> See below for a small example.
>
> library(parallel)
>
> clu <- makeCluster(2, "PSOCK")
>
> fun <- function(x0, x1) (x0 + x1)
> clusterApply(clu, x = 1:2, fun = fun, x1 = 1) ## OK
> parLapply(cl = clu, X = 1:2, fun = fun, x1 = 1) #OK
>
>
> fun <- function(b, c) (b + c)
> clusterApply(clu, x = 1:2, fun = fun, c = 1) ## Error
> clusterApply(cl = clu, x = 1:2, fun = fun, c = 1) ## OK
> parLapply(cl = clu, X = 1:2, fun = fun, c = 1) ## Error
>
> stopCluster(clu)
>
>
> I used "R version 3.4.3 Patched (2018-01-07 r74099".
>
>
> Best regards,
> Florian
>
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