system.time
CPU Time Used
Description
Calculates the CPU time that "expr" uses.
Usage
system.time(expr, gcFirst = TRUE)
unix.time(expr, gcFirst = TRUE)
Arguments
expr |
an expression that takes CPU time.
|
gcFirst |
a logical value. If TRUE (the default), specifies that garbage collection occurs before timing "expr".
|
Details
if "expr" is omitted, system.time retrieves the CPU usage time and shows the error condition.
If any child processes are spawned during the current session, system.time cumulates them to user and system times.
Value
returns a numeric vector of class
proc_time, identified by:
- "user.self"
- "sys.self"
- "elapsed"
- "user.child"
- "sys.child"
giving the user, system, and elapsed times for the currently running engine process,
in units of seconds.
The print and summary methods for proc_time add the child times to the corresponding
self times and labels them "user", "system", and "elapsed".
See Also
Examples
timeLinearAlgebra <- function(n)
{
MatA <- matrix(log2(seq_len(29*31)), nrow=29, ncol=31)
MatB <- matrix(seq_len(31*37), nrow=31, ncol=37)
# elapsed less than user+system on multicore machine
system.time(for(i in seq_len(n)) MatA %*% MatB)
}
timeLinearAlgebra(10000)
timeFileAccess <- function(n)
{
tf <- tempfile()
on.exit(unlink(tf))
# lots of system time, lots more elapsed time
system.time(for(i in seq_len(n))cat(file=tf, i, "\n", sep=""))
}
timeFileAccess(5000)