On 22/02/2012 07:53, Martin Maechler wrote:
"LS" == Libo Sun<libo...@rams.colostate.edu>
on Tue, 21 Feb 2012 21:09:54 -0700 writes:
> Thanks. Shall I sum the user time and system time, which
> roughly equals to the elapsed time?
No. Rather just use the user time,
i.e. proc.time()[[1]]
system.time()[[1]] etc
That's typically good enough [as long as you don't use
internally multithreaded BLAS, or parallelize / distribute your job,
or other things you won't be doing (yet)].
I think the original suggestion was better, and e.g. R CMD check reports
the sum of user+system as the CPU time.
This is platform-dependent, and on some platforms there can be
substantial CPU for your process which is accounted as system time.
(I've seen it most often on OS X, but not only there.)
The other issue is the fourth and fifth entries, time for children,
which as Martin says is only for advanced users (and not reported on
Windoww).
Martin Maechler, ETH Zurich
> I also tried to improve the code by using 'cmpfun(myfunction)' in
> 'compiler' package, however, it doesn't help too much.
> Libo
On Tue, Feb 21, 2012 at 8:11 PM, R. Michael Weylandt<
michael.weyla...@gmail.com> wrote:
The time relationships aren't strictly linear between any of the three
measures, but *very generally* I've interpreted them as something
like:
User: stuff you do (i.e., doing all the commands)
System: stuff at the OS level (memory allocations and whatnot)
Elapsed: Clock time
None is a great measure in isolation, but the system time is not the
worrisome one here: it looks like your script takes about a day and a
half to run....that might be ok (and perhaps unavoidable) but it looks
like there might be value in trying to squeeze some speed out of your
script. A simple thing like byte-compiling that gives 2x speedup would
be huge here.
Michael
On Tue, Feb 21, 2012 at 10:06 PM, Libo Sun<libo...@rams.colostate.edu>
wrote:
Hi all,
I got this time for my code,
proc.time()-pt
user system elapsed
132541.743 0.004 132533.526
As you can see, there is huge difference btw elapsed time and system
time.
Does that mean lots of I/O? Or some bad coding?
Thanks,
Libo
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