On 3/28/2007 5:25 PM, Henrik Bengtsson wrote: > Hi, > > when doing as.double() on an object that is already a double, the > object seems to be copied internally, doubling the memory requirement. > See example below. Same for as.character() etc. Is this intended? > > Example: > > % R --vanilla >> x <- double(1e7) >> gc() > used (Mb) gc trigger (Mb) max used (Mb) > Ncells 234019 6.3 467875 12.5 350000 9.4 > Vcells 10103774 77.1 11476770 87.6 10104223 77.1 >> x <- as.double(x) >> gc() > used (Mb) gc trigger (Mb) max used (Mb) > Ncells 234113 6.3 467875 12.5 350000 9.4 > Vcells 10103790 77.1 21354156 163.0 20103818 153.4 > > However, couldn't this easily be avoided by letting as.double() return > the object as is if already a double?
as.double calls the internal as.vector, which also strips off attributes. But in the case where the output is identical to the input, this does seem like an easy optimization. I don't know if it would help most people, but it might help in the kinds of cases you mention. Duncan Murdoch > > Example: > > % R --vanilla >> as.double.double <- function(x, ...) x >> x <- double(1e7) >> gc() > used (Mb) gc trigger (Mb) max used (Mb) > Ncells 234019 6.3 467875 12.5 350000 9.4 > Vcells 10103774 77.1 11476770 87.6 10104223 77.1 >> x <- as.double(x) >> gc() > used (Mb) gc trigger (Mb) max used (Mb) > Ncells 234028 6.3 467875 12.5 350000 9.4 > Vcells 10103779 77.1 12130608 92.6 10104223 77.1 > > What's the catch? > > > The reason why I bring it up, is because many (most?) methods are > using as.double() etc "just in case" when passing arguments to > .Call(), .Fortran() etc, e.g. stats::smooth.spline(): > > fit <- .Fortran(R_qsbart, as.double(penalty), as.double(dofoff), > x = as.double(xbar), y = as.double(ybar), w = as.double(wbar), <etc>) > > Your memory usage is peaking in the actual call and the garbage > collector cannot clean it up until after the call. This seems to be > waste of memory, especially when the objects are large (100-1000MBs). > > Cheers > > Henrik > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
