[Rd] slow load() in R2.6.0

[Mark.Bravington at csiro.au]

I'm encountering excruciatingly slow load times for character vectors in
R 2.6.0-- up to 30sec for a 15K file that contains a no-attributes
character vector of length ~1e4 and object size ~0.5MB. In R 2.5.1,
repeated loads of the same set of files are near-instantaneous.

The problem is proving tricky to reproduce consistently from scratch, so
I have attached the 3 files used in the examples below. If I create a
similar-looking object from scratch, then save it and re-load it a few
times, the problem doesn't always occur... at least not in that session.


FWIW I have noticed that the time taken to load seems to be roughly a
power of 2 of the "base slow load time"-- could be a red herring.

The problem seems specific to character vectors-- I noticed it with
entire workspaces and have whittled it down to char vecs only.

The example below is from a brand-new session with only the basic
packages loaded; delays in my real sessions are much longer.


Mark Bravington
CSIRO Mathematical & Information Sciences
Marine Laboratory
Castray Esplanade
Hobart 7001
TAS

ph (+61) 3 6232 5118
fax (+61) 3 6232 5012
mob (+61) 438 315 623



Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.

> system.time( load( 'd:/r2.0/t1.rda'))
   user  system elapsed 
    0.5     0.0     0.5 
> system.time( load( 'd:/r2.0/t1.rda')) # same file; slower
   user  system elapsed 
    3.5     0.0     3.5 
> system.time( load( 'd:/r2.0/t1.rda'))
   user  system elapsed 
   4.13    0.00    4.13 
> system.time( load( 'd:/r2.0/t1.rda'))
   user  system elapsed 
   3.51    0.00    3.52 

> system.time( load( 'd:/r2.0/t2.rda'))  # different bigger file
   user  system elapsed 
   4.42    0.00    4.42 
> system.time( load( 'd:/r2.0/t2.rda')) # same file; slower
   user  system elapsed 
  10.44    0.00   10.44 
> system.time( load( 'd:/r2.0/t2.rda'))
   user  system elapsed 
  10.79    0.00   10.80 
> system.time( load( 'd:/r2.0/t2.rda'))
   user  system elapsed 
  10.39    0.00   10.41 
> system.time( load( 'd:/r2.0/t1.rda')) # the smaller file again; slower
   user  system elapsed 
  10.67    0.00   10.69 
> system.time( load( 'd:/r2.0/t3.rda')) # different smaller file
   user  system elapsed 
  10.51    0.00   10.52 
> system.time( load( 'd:/r2.0/t2.rda')) # now bigger file again: slower
   user  system elapsed 
  14.61    0.00   14.61 



--please do not edit the information below--

Version:
 platform = i386-pc-mingw32
 arch = i386
 os = mingw32
 system = i386, mingw32
 status = 
 major = 2
 minor = 6.0
 year = 2007
 month = 10
 day = 03
 svn rev = 43063
 language = R
 version.string = R version 2.6.0 (2007-10-03)

Windows XP (build 2600) Service Pack 2.0

Locale:
LC_COLLATE=English_Australia.1252;LC_CTYPE=English_Australia.1252;LC_MON
ETARY=English_Australia.1252;LC_NUMERIC=C;LC_TIME=English_Australia.1252

Search Path:
Search Path:
 .GlobalEnv, package:stats, package:graphics, package:grDevices,
package:utils, package:datasets, package:methods, Autoloads,
package:base