| % File src/library/base/man/system.time.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2016 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{system.time} |
| \title{CPU Time Used} |
| \usage{ |
| system.time(expr, gcFirst = TRUE) |
| %Deprecated unix.time(expr, gcFirst = TRUE) |
| } |
| \alias{system.time} |
| \alias{unix.time} |
| \arguments{ |
| \item{expr}{Valid \R expression to be timed.} |
| \item{gcFirst}{Logical - should a garbage collection be performed |
| immediately before the timing? Default is \code{TRUE}.} |
| } |
| \description{Return CPU (and other) times that \code{expr} used. |
| } |
| \details{ |
| \code{system.time} calls the function \code{\link{proc.time}}, |
| evaluates \code{expr}, and then calls \code{proc.time} once more, |
| returning the difference between the two \code{proc.time} calls. |
| |
| \code{unix.time} has been an alias of \code{system.time}, for |
| compatibility with S, and has finally been deprecated in 2016. |
| |
| Timings of evaluations of the same expression can vary considerably |
| depending on whether the evaluation triggers a garbage collection. When |
| \code{gcFirst} is \code{TRUE} a garbage collection (\code{\link{gc}}) |
| will be performed immediately before the evaluation of \code{expr}. |
| This will usually produce more consistent timings. |
| } |
| \value{ |
| A object of class \code{"proc_time"}: see |
| \code{\link{proc.time}} for details. |
| } |
| \seealso{ |
| \code{\link{proc.time}}, \code{\link{time}} which is for time series. |
| |
| \code{\link{Sys.time}} to get the current date & time. |
| } |
| \examples{ |
| require(stats) |
| \donttest{system.time(for(i in 1:100) mad(runif(1000)))} |
| \dontrun{ |
| exT <- function(n = 10000) { |
| # Purpose: Test if system.time works ok; n: loop size |
| system.time(for(i in 1:n) x <- mean(rt(1000, df = 4))) |
| } |
| #-- Try to interrupt one of the following (using Ctrl-C / Escape): |
| exT() #- about 4 secs on a 2.5GHz Xeon |
| system.time(exT()) #~ +/- same |
| }} |
| \keyword{utilities} |