[Rd] Slow try in combination with do.call
Martin Maechler
m@ech|er @end|ng |rom @t@t@m@th@ethz@ch
Tue Oct 12 12:43:04 CEST 2021
Just in case, you hadn't noticed:
Since Sep.17, we have had the faster try() now in both R-devel
and "R 4.1.1 patched" which will be released as R 4.1.2 by the
end of this month, with NEWS entry
• try() is considerably faster in case of an error and long call,
as e.g., from some do.call(). Thanks to Alexander Kaever's
suggestion posted to R-devel.
Martin
>>>>> nospam using altfeld-im de
>>>>> on Tue, 12 Oct 2021 12:11:10 +0200 writes:
> In fact an attentive user reported the same type of (slow due to deparse) problem in may tryCatchLog package recently when using a large sparse matrix
> https://github.com/aryoda/tryCatchLog/issues/68
> and I have fixed it by explicitly using the nlines arg of deparse() instead of using as.character()
> which implicitly calls deparse() for a call stack.
> Looking for a fix I think I may have found inconsistent deparse default arguments in base R between as.character() and deparse():
> A direct deparse call in R uses
> control = c("keepNA", "keepInteger", "niceNames", "showAttributes")
> as default (see ?.deparseOpts for details).
> The as.character() implementation in the C code of base R calls the internal deparse C function
> with another default for .deparseOpts:
> The SIMPLEDEPARSE C constant which corresponds to control = NULL.
> https://github.com/wch/r-source/blob/54f94f0433c487fe55553b0df9bae477c9babdd1/src/main/deparse.c#L345
> This is clearly no bug but maybe the as.character() implementation should use the default args of deparse() for consistency (just a proposal!)...
> BTW: You can find my analysis result with the call path and links to the R source code in the github issue:
> https://github.com/aryoda/tryCatchLog/issues/68#issuecomment-930593002
> On Thu, 2021-09-16 at 18:04 +0200, Martin Maechler wrote:
>> > > > > > 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
>>
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