# [Rd] Problem with function in fortran 95

Fabio Mathias Corrêa fabio.ufla at yahoo.com.br
Fri Aug 14 11:37:09 CEST 2009

```Thanks very much!!!

Fábio Mathias Corrêa
Estatística e Experimentação Agropecuária/UFLA

--- Em sex, 14/8/09, Simone Giannerini <sgiannerini at gmail.com> escreveu:

> De: Simone Giannerini <sgiannerini at gmail.com>
> Assunto: Re: [Rd] Problem with function in fortran 95
> Para: "Fabio Mathias Corrêa" <fabio.ufla at yahoo.com.br>
> Cc: r-devel at r-project.org
> Data: Sexta-feira, 14 de Agosto de 2009, 9:19
> Fabio,
>
> I see two problems with your code:
>
> 1. R type numeric corresponds to FORTRAN Real*8 (or double
> precision)
> so that line 4 of your mat.f95 becomes:
>
> REAL*8 :: x, y, res
>
> 2. your R code won't ever succeed because you pass integer
> matrices
> (x,y,res) to a subroutine that expects REAL*8 data.
> you need to coerce all your matrices to "double" as
> follows:
>
> storage.mode(x) <- "double"
> storage.mode(y) <- "double"
> storage.mode(res) <- "double"
>
> Finally, you can call the corrected function:
>
> .Fortran("mymult", x,y,res,as.integer(l),as.integer(c))
> [[1]]
>      [,1] [,2] [,3] [,4]
> [1,]    1
> 6   11   16
> [2,]    2
> 7   12   17
> [3,]    3
> 8   13   18
> [4,]    4
> 9   14   19
> [5,]
> 5   10   15   20
>
> [[2]]
>      [,1] [,2] [,3] [,4] [,5]
> [1,]   20   16   12
>   8    4
> [2,]   19   15   11
>   7    3
> [3,]   18   14   10
>   6    2
> [4,]   17   13
> 9    5    1
>
> [[3]]
>      [,1] [,2] [,3] [,4] [,5]
> [1,]  604  468  332
> 196   60
> [2,]  678  526  374
> 222   70
> [3,]  752  584  416
> 248   80
> [4,]  826  642  458
> 274   90
> [5,]  900  700  500  300  100
>
> [[4]]
> [1] 5
>
> [[5]]
> [1] 4
>
>
> All these issues are discussed in the "Writing R
> Extensions" manual,
>
> Ciao
>
> Simone
>
>
>
> On Wed, Aug 12, 2009 at 1:32 PM, Fabio Mathias
> Corrêa<fabio.ufla at yahoo.com.br>
> wrote:
> > I am writing a function in fortran 95, but the
> intrinsic function MATMUL is not working properly. Here's an
> example.
> >
> >        SUBROUTINE mymult(x,y,res,m,n)
> >        IMPLICIT NONE
> >        INTEGER :: m,n
> >        REAL :: x, y, res
> >        DIMENSION :: x(m,n), y(n,m), res(m,m)
> >        res = MATMUL(x,y)
> >        END SUBROUTINE mymult
> >
> > R CMD SHLIB mat.f95
> >
> > In R:
> >
> > x   <- matrix(1:20,5)
> > l   <- nrow(x)
> > c   <- ncol(x)
> > y   <- matrix(20:1,c)
> > res <- matrix(0,l,l)
> > dim(x)
> > dim(y)
> > dim(res)
> > l
> > c
> > .Fortran("mymult", x,y,res,l,c)
> >
> > [[1]]
> >     [,1] [,2] [,3] [,4]
> > [1,]    1    6   11   16
> > [2,]    2    7   12   17
> > [3,]    3    8   13   18
> > [4,]    4    9   14   19
> > [5,]    5   10   15   20
> >
> > [[2]]
> >     [,1] [,2] [,3] [,4] [,5]
> > [1,]   20   16   12    8    4
> > [2,]   19   15   11    7    3
> > [3,]   18   14   10    6    2
> > [4,]   17   13    9    5    1
> >
> > [[3]]
> >     [,1] [,2] [,3] [,4] [,5]
> > [1,]    0    0    0    0    0
> > [2,]    0    0    0    0    0
> > [3,]    0    0    0    0    0
> > [4,]    0    0    0    0    0
> > [5,]    0    0    0    0    0
> >
> > [[4]]
> > [1] 5
> >
> > [[5]]
> > [1] 4
> >
> >
> > Linux Ubuntu 8.04 and use compiler gfortran 4.2.
> > The problem is the compiler?
> >
> > Thanks!
> >
> >                Fábio Mathias Corrêa
> > Estatística e Experimentação Agropecuária/UFLA
> >                      Brazil
> >
> >
> >
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> mailing list
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> >
>
>
>
> --
> ______________________________________________________
>
> Simone Giannerini
> Dipartimento di Scienze Statistiche "Paolo Fortunati"
> Universita' di Bologna
> Via delle belle arti 41 - 40126  Bologna,  ITALY
> Tel: +39 051 2098262  Fax: +39 051 232153
> http://www2.stat.unibo.it/giannerini/
> ______________________________________________________
>

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