R devel - Mar 2010 - strptime(): on Linux system it seems to call system time?

[I am herewith re-posting this message on R-devel, as it seems to be the
most appropriate mailing list for this issue.]

 

Dear List,

 
>From what I understand, strptime() simply converts from one class
representation to another; i.e., from character to POSIXct/POSIXlt.

 

One strange feature of this command running on Linux is that there are
repeated calls to system time (as was revealed in a trace of system
calls), which considerably affect performance.  These system calls end
up taking almost 75% of the execution time, and are completely
unnecessary.

 

Code:

ptm <- proc.time()

for (i in 1:100000) strptime("2010-03-10 17:00:00", "%F
%H:%M:%S")

(proc.time() -ptm)

 

Output on Windows Box (32-bit R 2.9.1 running on Intel X5472 @ 3.0 GHz):

   user  system elapsed 

   1.31    0.02    1.30

 

Output on Linux Box (64-bit R 2.10.1 running on Intel Xeon E5520 @
2.27GHz):

   user  system elapsed 

   3.33    8.941    12.273

 

Any help would be appreciated.  Also, if I should turn to a different
mailing list for this, please let me know.

 

Regards,

Alex  


	[[alternative HTML version deleted]]

Alexander Peterhansl wrote:
> [I am herewith re-posting this message on R-devel, as it seems to be the
> most appropriate mailing list for this issue.]
> 
>  
> 
> Dear List,
> 
>  
> 
>>From what I understand, strptime() simply converts from one class
> representation to another; i.e., from character to POSIXct/POSIXlt.
> 
>  
> 
> One strange feature of this command running on Linux is that there are
> repeated calls to system time (as was revealed in a trace of system
> calls), which considerably affect performance.  These system calls end
> up taking almost 75% of the execution time, and are completely
> unnecessary.
> 
>  
> 
> Code:
> 
> ptm <- proc.time()
> 
> for (i in 1:100000) strptime("2010-03-10 17:00:00", "%F
%H:%M:%S")
> 
> (proc.time() -ptm)
> 
>  
> 
> Output on Windows Box (32-bit R 2.9.1 running on Intel X5472 @ 3.0 GHz):
> 
>    user  system elapsed 
> 
>    1.31    0.02    1.30
> 
>  
> 
> Output on Linux Box (64-bit R 2.10.1 running on Intel Xeon E5520 @
> 2.27GHz):
> 
>    user  system elapsed 
> 
>    3.33    8.941    12.273
> 
>  
> 
> Any help would be appreciated.  Also, if I should turn to a different
> mailing list for this, please let me know.
It seems to be  completely system-dependent. On Fedora 9, I see

   user  system elapsed
  2.890   0.314   3.374

but on openSUSE 10.3 it is

   user  system elapsed
  3.924   6.992  10.917

At any rate, I suspect that this is an issue with the operating system
and its C libraries, not with R as such.


-- 
Peter Dalgaard
Center for Statistics, Copenhagen Business School
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com

On Sat, 20-Mar-2010 at 06:54PM +0100, Peter Dalgaard wrote:

[...]

|> It seems to be  completely system-dependent. On Fedora 9, I see
|> 
|>    user  system elapsed
|>   2.890   0.314   3.374
|> 
|> but on openSUSE 10.3 it is
|> 
|>    user  system elapsed
|>   3.924   6.992  10.917
|> 
|> At any rate, I suspect that this is an issue with the operating system
|> and its C libraries, not with R as such.

Were those 32 or 64 bit?

With Fedora 11 and AMD Athlon 2 Ghz, I get

   user  system elapsed 
  1.395   0.294   1.885 

with Mepis 7 on a Celeron 1.6 Ghz,

   user  system elapsed 
  3.890   5.896   9.845 

Both of those are 32 bit.  
Maybe 64 bit does things very differently.



-- 
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   ___    Patrick Connolly   
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 _( Y )_  	         Average minds discuss events 
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