I can give you the answer to #1. If you had put a "print(str(m))" you
would have seen that initially the matrix was setup as logical which
requires 4 bytes per element. On the first assignment of a numeric, the
mode of 'm' is changed to numeric which requires 8 bytes per element; that
is the reason for the "doubling".
On Mon, Jul 15, 2013 at 6:50 PM, ivo welch <ivo.we...@anderson.ucla.edu>wrote:
> dear R experts: I am curious again about R memory allocation strategies.
> Consider an intentionally inefficient program:
>
> ranmatme <- function( lx, rx ) {
> m <- matrix(NA, nrow=lx, ncol=rx)
> for (li in 1:rx) {
> cat("\tLag i=", li, "object size=", object.size(m), "\n")
> m[,li] <- rnorm(lx)
> }
> m
> }
>
> v <- ranmatme( 1024*1024*128, 3 )
>
>
> [1] on the first cat, the object size is only 1.6GB, which is half the size
> of the 3.2GB that it is on the 2nd and 3rd call. why?
>
> [2] I tried to monitor the linux memory allocation in another window. I
> could be completely wrong, but it seems that upon function exit, memory
> usage spikes briefly. it is almost as if there was an explicit copy of m
> into v, and both had to exist simultaneously for a moment in time. is this
> the case? (if so, is there a way to return and assign just the reference?
> I may be blanking here---maybe the answer is obvious.)
>
> regards,
>
> /iaw
> ----
> Ivo Welch (ivo.we...@gmail.com)
>
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>
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>
--
Jim Holtman
Data Munger Guru
What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.
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