Benchmark code, but avoid printing

Fri, Jan 2, 2015 1:20 PM

Yes, thanks much, this makes a lot of sense.

Well, by "better" what I had in mind was something that is reliably
close to the time needed for printing. Without actually doing the
printing. But I realize this is too much to ask for, and I'll be fine
with /dev/null. Thanks for bringing up the textConnection() issue as
well, especially because I am using textConnection now. /dev/null is a
better option.

Best,
Gabor

On Fri, Jan 2, 2015 at 3:44 PM, Simon Urbanek

<simon.urbanek at r-project.org> wrote:

On Jan 2, 2015, at 12:02 PM, G?bor Cs?rdi <csardi.gabor at gmail.com> wrote:

Dear all,

I am trying to benchmark code that occasionally prints on the screen
and I want to
suppress the printing. Is there an idiom for this?

If I do

sink(tempfile)
microbenchmark(...)
sink()

then I'll be also measuring the costs of writing to tempfile. I could
also sink to /dev/null, which is probably fast, but that is not
portable.

Is there a better solution? Is writing to a textConnection() better?

Define better - you're just trading off one output code for another - it will be still measuring the cost of the output, obviously, and since the output is part of the code you're profiling it's correctly so. Each output method has different beavior - e.g. text connection can be faster, but it can also trigger additional garbage collection so it will affect results. Example:

f=textConnection("x", "w")
sink(f)
m=microbenchmark({ for (i in 1:100) { print("foo"); sum(rnorm(1e3)) } })
sink()
m

Unit: milliseconds
                                                                           expr
 {     for (i in 1:100) {         print("foo")         sum(rnorm(1000))     } }
      min       lq     mean   median       uq      max neval
 12.76462 15.34483 17.85341 17.02435 19.56384 63.09329   100

sink("/dev/null")
m=microbenchmark({ for (i in 1:100) { print("foo"); sum(rnorm(1e3)) } })
sink()
m

Unit: milliseconds
                                                                           expr
 {     for (i in 1:100) {         print("foo")         sum(rnorm(1000))     } }
     min       lq     mean  median       uq      max neval
 13.0191 13.03601 13.41815 13.0534 13.16496 16.25288   100

As you can see /dev/null is more predictable, because it's straight output, but text connection can be faster in the beginning and becomes progressively slower.

As Henrik said, you're probably best off using simply /dev/null - the only oddball is Windows, and that's a trivial condition on .Platform$OS.type.

Cheers,
S

Benchmark code, but avoid printing

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