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? Thanks, Best, Gabor
On Fri, Jan 2, 2015 at 9:02 AM, 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.Interesting problem. On Windows NUL corresponds to /dev/NULL, e.g. con <- file("NUL", open="wb"). Not that it's cross platform, but it at least allows you to cover on more OS. Maybe R should have a built-in "null" device. An easier solution is probably to go back to the maintainers of the functions outputting text and ask them for an option to disable that.> > Is there a better solution? Is writing to a textConnection() better?For large number of output *lines* (not characters), textConnection() is exponentially slow (at least in R 3.1.0). Use rawConnection() instead, cf. http://www.jottr.org/2014/05/captureOutput.html /Henrik> > Thanks, Best, > Gabor > > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel
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() > mUnit: 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() > mUnit: 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
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 >