thx, jim. makes perfect sense now.
I guess a logical in R has a few million possible values ;-).
(Joke. I realize that 4 bytes is to keep the code convenient and faster.)
regards,
/iaw
----
Ivo Welch (ivo.we...@gmail.com)
On Mon, Jul 15, 2013 at 4:26 PM, jim holtman <jholt...@gmail.com> wrote:
> 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)
>>
>> [[alternative HTML version deleted]]
>>
>> ______________________________________________
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>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>
>
> --
> 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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