dget() much slower in recent R versions

On 20/06/2014 15:37, Ista Zahn wrote:

Hello,

I've noticed that dget() is much slower in the current and devel R
versions than in previous versions. In 2.15 reading a 10000-row
data.frame takes less than half a second:

(which.r <- R.Version()$version.string)

[1] "R version 2.15.2 (2012-10-26)"

x <- data.frame(matrix(sample(letters, 100000, replace = TRUE), ncol
= 10))
dput(x, which.r)
system.time(y <- dget(which.r))

    user  system elapsed
   0.546   0.033   0.586

While in 3.1.0 and r-devel it takes around 7 seconds.

(which.r <- R.Version()$version.string)

[1] "R version 3.1.0 (2014-04-10)"

x <- data.frame(matrix(sample(letters, 100000, replace = TRUE), ncol
= 10))
dput(x, which.r)
system.time(y <- dget(which.r))

    user  system elapsed
   6.920   0.060   7.074

(which.r <- R.Version()$version.string)

[1] "R Under development (unstable) (2014-06-19 r65979)"

x <- data.frame(matrix(sample(letters, 100000, replace = TRUE), ncol
= 10))
dput(x, which.r)
system.time(y <- dget(which.r))

    user  system elapsed
   6.886   0.047   6.943

I know dput/dget is probably not the right tool for this job:
nevertheless the slowdown in quite dramatic so I thought it was worth
calling attention to.

This is completely the wrong way to do this. See ?dump.

dget() basically calls eval(parse()).  parse() is much slower in R >=
3.0 mainly because it keeps more information.  Using keep.source=FALSE
here speeds things up a lot.

 > system.time(y <- dget(which.r))

    user  system elapsed
   3.233   0.012   3.248

 > options(keep.source=FALSE)
 > system.time(y <- dget(which.r))

    user  system elapsed
   0.090   0.001   0.092