[R] outer(-x, x, pmin) cannot allocate

[Berton Gunter]

David:

In general, this is not a good question to ask, as one needs to go into the
bowels of R to find an answer.

But note that 8000 x 8000 x 4 bytes for double precision  = 256 mb. Now look
at the code of outer(). Two vectors of this size are created = 512mb. Then
copies of these must be created to be passed into pmin, I believe, as R
passes by value. That's 1gb.

My guess is that "+", as an internal function, avoids the final doubling.

Corrections/clarifications by knowledgeable R experts cheerfully welcomed.
I'm on thin ice here.

-- Bert Gunter
Genentech Non-Clinical Statistics
South San Francisco, CA
 
"The business of the statistician is to catalyze the scientific learning
process."  - George E. P. Box
 
 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Brahm, David
> Sent: Wednesday, December 22, 2004 12:11 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] outer(-x, x, pmin) cannot allocate
> 
> R> x <- 0. + 1:8000
> R> y <- outer(-x, x, pmin)
> Error: cannot allocate vector of size 1000000 Kb
> 
> Why does R need to allocate a gigabyte to create an 8000 x 
> 8000 matrix?
> It doesn't have any trouble with outer(-x, x, "+").  Thanks.
> 
> -- David Brahm (brahm at alum.mit.edu)
> 
> Version:
>  platform = i686-pc-linux-gnu
>  arch = i686
>  os = linux-gnu
>  system = i686, linux-gnu
>  status = 
>  major = 2
>  minor = 0.1
>  year = 2004
>  month = 11
>  day = 15
>  language = R
> 
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