[Rd] Slow try in combination with do.call

[Martin Maechler]

>>>>> Martin Maechler 
>>>>>     on Thu, 16 Sep 2021 17:48:41 +0200 writes:

>>>>> Alexander Kaever 
>>>>>     on Thu, 16 Sep 2021 14:00:03 +0000 writes:

    >> Hi,
    >> It seems like a try(do.call(f, args)) can be very slow on error depending on the args size. This is related to a complete deparse of the call using deparse(call)[1L] within the try function. How about replacing deparse(call)[1L] by deparse(call, nlines = 1)?

    >> Best,
    >> Alex

    > an *excellent* idea!

    > I have checked that the resulting try() object continues to contain the
    > long large call; indeed that is not the problem, but the
    > deparse()ing  *is* as you say above.

    > {The experts typically use  tryCatch() directly, instead of  try() ,
    > which may be the reason other experienced R developers have not
    > stumbled over this ...}

    > Thanks a lot, notably also for the clear  repr.ex. below.

    > Best regards,
    > Martin

OTOH, I find so many cases  of   deparse(*)[1]  (or similar) in
R's own sources, I'm wondering
if I'm forgetting something ... and using nlines=* is not always
faster & equivalent and hence better ??

Martin




    >> Example:

    >> fun <- function(x) {
    >> stop("testing")
    >> }
    >> d <- rep(list(mtcars), 10000)
    >> object.size(d)
    >> # 72MB

    >> system.time({
    >> try(do.call(fun, args = list(x = d)))
    >> })
    >> # 8s