[Rcpp-devel] Performance question about DataFrame

[John Merrill]

As of 2.15.1, data.frame appears to no longer be O(n^2) in the number of
columns in the frame.  That's certainly an improvement, yes.

However, by eliminating calls to data.frame and replacing them with direct
class modifications, I can take a routine which takes minutes and reduce it
to a routine which takes seconds.  So, pragmatically, in Rcpp, I can get a
rough factor of sixty, it appears.


On Thu, Jan 17, 2013 at 7:46 PM, Paul Johnson <pauljohn32 at gmail.com> wrote:

> On Tue, Jan 15, 2013 at 9:20 AM, John Merrill <john.merrill at gmail.com>
> wrote:
> > It appears that DataFrame::create is a thin layer on top of the R
> data.frame
> > call.  The guarantee correctness, but also means the performance of an
> Rcpp
> > routine which returns a large data frame is limited by the performance of
> > data.frame -- which is utterly horrible.
>
> Are you certain that this claim is still true?
>
> I was shocked/surprised by the package "dataframe" and the commentary
> about it. The author said that data.frame was slow because "This
> contains versions of standard data frame functions in R, modified to
> avoid making extra copies of inputs. This is faster, particularly for
> large data."
>
> it was repeatedly copying some objects and he proved a substantially
> faster approach.
>
> In the release notes for R-2.15.1, I recall seeing a note that R Core
> had responded by integrating several of those changes. But still
> data.frame is not fast for you?
>
> If they didn't make the core data.frame as fast, would you care to
> enlighten us by installing the dataframe package and letting us know
> if it is still faster?
>
> Or perhaps you are way ahead of me and you've already imitated
> Hesterberg's algorithms in your C++ design?
>
> pj
>
> --
> Paul E. Johnson
> Professor, Political Science      Assoc. Director
> 1541 Lilac Lane, Room 504      Center for Research Methods
> University of Kansas                 University of Kansas
> http://pj.freefaculty.org               http://quant.ku.edu
>
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