[R] Meaning of proc.time()

[jim holtman]

This is reporting on the accumulated values of the user CPU, system
CPU and elapsed time.  The 'user + system' values indicate how much
CPU has been used to process whatever has occurred in the R session so
far.  To get the time to execute a statement, or block of code, you
can use 'system.time' or take the difference in two values of
proc.time:

> a <- proc.time()
> for(i in 1:1e6) x <- 1
> proc.time() - a  # elapsed
   user  system elapsed
   0.38    0.05   42.48
>

Here is some stuff I typed in at the console.  It took me 42 seconds
(elapsed or wall clock time) to type in the commands to the GUI.  I
executed a simple 'for' loop for 1,000,000 iteration and this required
0.43 CPU seconds (user + system).

> a <- proc.time()
> for(i in 1:1e7) x <- 1
> proc.time() - a  # elapsed
   user  system elapsed
   3.33    0.03   18.14
>

Notice that I executed the 'for' loop 10,000,000 times and the CPU
time is now 3.36 seconds, or about 10X more than the first one which
is about what you would expect.   This is a common way of determining
what portions of your script are taking the most resource.

HTH

On Tue, Jul 27, 2010 at 4:03 AM, Christofer Bogaso
<bogaso.christofer at gmail.com> wrote:
> If I run proc.time() function, I would get following:
>
>> proc.time()
>    user  system elapsed
>    2.82    4.18  792.39
>
> However I am struggling the meaning of the object what it returned. In
> help file it says that:
>
> "user time" is the time required to execute the calling process. Here
> what is the calling process exactly? Who executes this? system itself?
>
> 2ndly "system time" is the time required by the system for execution
> of something.......... what execution? What is the meaning of " on
> behalf of the
>      calling process?"
>
> 3rdly what is elapsed time? Total time I spent on current session,
> since I opened the R window?
>
> Really sorry if I asked trivial questions, however honestly I could
> not understand those. Some helpful comments are highly appreciated.
>
> Thanks,
>
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>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?