system.time {base} | R Documentation |
Return CPU (and other) times that expr
used.
system.time(expr, gcFirst = TRUE) unix.time(expr, gcFirst = TRUE)
expr |
Valid R expression to be “timed” |
gcFirst |
Logical - should a garbage collection be performed
immediately before the timing? Default is TRUE . |
system.time
calls the builtin proc.time
,
evaluates expr
, and then calls proc.time
once more,
returning the difference between the two proc.time
calls.
unix.time
is an alias of system.time
, for
compatibility reasons.
Timings of evaluations of the same expression can vary considerably
depending on whether the evaluation triggers a garbage collection. When
gcFirst
is TRUE
a garbage collection (gc
)
will be performed immediately before the evaluation of expr
.
This will usually produce more consistent timings.
A numeric vector of length 5 containing the user cpu, system cpu, elapsed,
subproc1, subproc2 times. The subproc times are the user and
system cpu time used by child processes (and so are usually zero).
The resolution of the times will be system-specific; it is common for
them to be recorded to of the order of 1/100 second, and elapsed
time is rounded to the nearest 1/100.
It is possible to compile R without support for system.time
,
when the function will throw an error.
proc.time
, time
which is for time series.
require(stats) system.time(for(i in 1:100) mad(runif(1000))) ## Not run: exT <- function(n = 1000) { # 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 3 secs on a 1GHz PIII system.time(exT()) #~ +/- same ## End(Not run)