[R-SIG-Mac] Different performance with different R versions

[Martin Maechler]

>>>>> Cowan, R (MERIT) 
>>>>>     on Thu, 13 Dec 2018 16:28:57 +0000 writes:

    > Comments below:
    >> On 13 Dec 2018, at 14:37, Martin Maechler <maechler using stat.math.ethz.ch> wrote:
    >> 
    >>>>>>> Peter Dalgaard 
    >>>>>>> on Wed, 12 Dec 2018 22:12:34 +0100 writes:
    >> 
    >>> I don't think there has been anything mentioned about slowdowns of that magnitude, but it's been 3.5 years since 3.1.3.
    >>> Would it be possible to narrow down what kind of code has become slow? 
    >> 

    > I explored a bit using Rprof() but made no progress. I can include the Rprof output if that might help. 
    > I will explore a bit more to see if I can narrow it down. But so far everything I have tried (cutting out various chunks of the simulation) has left the speed discrepancy intact. Which makes me think it is a very general thing, and quite possibly at a pretty low level (but that is guessing).

    >>> Since the OS version is different, I assume the first timing is historical and not easily redone, but if it is now using like 70 times as long as before, chances are that it is spending 69/70 of the time in the same few places.

    > The timing was done the same day. I have partitioned my hard drive and have two systems available, with different versions of R installed in each partition (part of the reason for this baroque structure is to be able to use the older faster R). But before going down the “it’s the two systems” road... I noticed this issue when a student ran the code on a brand new Macbook with R 3.5.1. I couldn’t believe how long it took him so tried it on my (old-ish) machine with the R 3.1.3, before I did the partitioning. And mine was 70 times faster.


    >> 
    >>> One generic frequent cause of grief with simulations is to keep onto the fitted models in entirety, including model frames etc., causing massive memory build-up.


    > The code is pretty simple so I doubt it is that, unless there was some major change in memory management between 3.1 and 3.5.

    >> 
    >>> -pd
    >> 
    >> If the  simulationR-R.R  script is basically reproducible
    >> (i.e. does not use data or other resources that only exist on
    >> your computer), it would  probably be useful if you "donated"
    >> it to the R project by making it publicly available.  Some of
    >> us do have many old R versions still running, and could quickly
    >> try and see…
    >> 

    > I would be very happy to do that. What is the best way to do so? (It only uses the igraph package.)

People use free download places, or Dropbox,..  The easiest
however, if the R script is not huge: you can rename it
simulation-R.txt {note the ending!} so your e-mail software
should mark it as text/plain  .. and text/plain attachments are
allowed on R-SIG-Mac.

But  "igraph" --> aha!  :
Do notice that in general, R 3.5.x  in many places is considerably
faster than R 3.1.x.
If the code depends on the igraph package -- which is not part
of R but an important addon package, heavily relying on compiled code --
are the timing differences perhaps only in those parts where you
use igraph functionality ?

If that's the case, this will still be very interesting and
important, but probably no longer so much for the R maintainers
(among whom Peter and I are), but rather the igraph author and
maintainer, i.e., maintainer("igraph"). ...

Please also provide a shortened version of sessionInfo() *after*
packages are loaded, for the R environments.



    > Thank you both for your help.

and thank you for trying more and Rprof()ing.
Yes, indeed an summaryRprof() may be revealing.

Best, Martin

    >> Martin Maechler (not a Mac user though)
    >> 
    >>>> On 12 Dec 2018, at 17:39 , Cowan, R (MERIT) <r.cowan using maastrichtuniversity.nl> wrote:
    >>>> 
    >>>> I am running a small simulation, and getting very different run times when I use different versions of R. 
    >>>> Two set-ups using the same machine (MacBook Pro 2013 vintage)
    >>>> 
    >>>> 1. R version 3.1.3  running on system OS X 10.9.5
    >>>> 
    >>>>> system.time(source("simulationR-R.R"))
    >>>> 
    >>>> user  system elapsed 
    >>>> 3.890   0.061   3.965 
    >>>> 
    >>>> Compared to
    >>>> 
    >>>> 2. R version 3.5.1  running on system OS X 10.12.6
    >>>> 
    >>>>> system.time(source("simulationR-R.R"))
    >>>> 
    >>>> user  system elapsed 
    >>>> 277.924   2.087 280.841 
    >>>> 
    >>>> The source code is identical. This is a pretty big difference running the same code on the same hardware.
    >>>> Before submitting the code, is this a known issue?
    >>>> 
    >>>> 
    >>>> Thanks,
    >>>> Robin Cowan
    >>>> _______________________________________________
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    >>>> R-SIG-Mac using r-project.org
    >>>> https://stat.ethz.ch/mailman/listinfo/r-sig-mac
    >> 
    >>> -- 
    >>> Peter Dalgaard, Professor,
    >>> Center for Statistics, Copenhagen Business School
    >>> Solbjerg Plads 3, 2000 Frederiksberg, Denmark
    >>> Phone: (+45)38153501
    >>> Office: A 4.23
    >>> Email: pd.mes using cbs.dk  Priv: PDalgd using gmail.com
    >> 
    >> 
    >>