R Language Code profiling proc.time()
Example
At its simplest, proc.time() gives the total elapsed CPU time in seconds for the current process. Executing it in the console gives the following type of output:
proc.time()
# user system elapsed
# 284.507 120.397 515029.305
This is particularly useful for benchmarking specific lines of code. For example:
t1 <- proc.time()
fibb <- function (n) {
if (n < 3) {
return(c(0,1)[n])
} else {
return(fibb(n - 2) + fibb(n -1))
}
}
print("Time one")
print(proc.time() - t1)
t2 <- proc.time()
fibb(30)
print("Time two")
print(proc.time() - t2)
This gives the following output:
source('~/.active-rstudio-document')
# [1] "Time one"
# user system elapsed
# 0 0 0
# [1] "Time two"
# user system elapsed
# 1.534 0.012 1.572
system.time() is a wrapper for proc.time() that returns the elapsed time for a particular command/expression.
print(t1 <- system.time(replicate(1000,12^2)))
## user system elapsed
## 0.000 0.000 0.002
Note that the returned object, of class proc.time, is slightly more complicated than it appears on the surface:
str(t1)
## Class 'proc_time' Named num [1:5] 0 0 0.002 0 0
## ..- attr(*, "names")= chr [1:5] "user.self" "sys.self" "elapsed" "user.child" ...
