[R] memory limitation with Fortran interface

[Göran Broström]

On Mon, Jan 19, 2004 at 12:19:06PM +0100, Guillot Gilles wrote:
> Hi,
> 
> I'm using R 7.0 under Linux as a programming interface to Fortran (g77 
> v0.5.24).
> Basically, what I want to do is to call a fortran subroutine of mine 
> which performs MCMC computations.
> Apparently I'm getting into memory management problems.
> 
> To track the problem I wrote  the following small Fortran subroutine 
> (saved as test.f) : 
> 
>       subroutine test(n,p)
>       implicit none
>       integer n,p,i,j
>       real x(n,p)
        ^^^^^^^^^^^

Two errors here:

1. You must allocate memory for x in the calling R function and have x as
an argument to 'test'

2. Use double precision ('double' in R)

Another recommendation is to write an  R  package for tasks like yours.
It is easier than you may think; see 'Writing R extensions'.

Göran

>       do i=1,n
>          do j=1,p
>             x(i,j) = 0
>             enddo
>          enddo
>       end
> 
> I compiled it by : 
> g77 -c test.f
> 
> then I called it from R with :
> 
> n <- 10000
> p <- 1000
> system("R CMD SHLIB ~/test.o")
> dyn.load("~/test.so")
> out.res<- .Fortran("test",
>                    as.integer(n),
>                    as.integer(p)
>                    )
> 
> causing R breakdown with the following message : 
> 
> Segmentation fault
> 
> I don't understand why this subroutine causes segmentartion fault 
> as its execution requires much less memory than what is existing  on my 
> machine (RAM 512 Mo RAM + swap 512 Mo ).
> 
> More generally, it seems that memory limitations are stronger
> when calling fortran code from R than when executing 
> the same Fortran subroutine from a bash command line.
> 
> 
> Gilles
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html

-- 
 Göran Broström                    tel: +46 90 786 5223
 Department of Statistics          fax: +46 90 786 6614
 Umeå University                   http://www.stat.umu.se/egna/gb/
 SE-90187 Umeå, Sweden             e-mail: gb at stat.umu.se