Berwin,
Many thanks, adding a statement:
double precision ddot
at the top fixed the problem! Once I add that the printing to screen works
well too.
Based on what you're telling me about the expected types when not declared,
I'm surprised the code ever worked at all!
Regards,
Emmanuel
On Sat, Jan 11, 2014 at 11:26 PM, Berwin A Turlach <berwin.turl...@gmail.com
> wrote:
> G'day Emmanuel,
>
> On Sat, 11 Jan 2014 14:08:41 -0800
> Emmanuel Sharef <esha...@gmail.com> wrote:
>
> > Example: this program creates two double vectors, takes the dot
> > product with ddot, and prints the result:
> >
> > test.f:
> > subroutine testddot(n,x,y)
> > integer i,n
> > double precision x,y,d1(n),d2(n)
> > do 100 i=1,n
> > d1(i)=x
> > d2(i)=y
> > 100 continue
> > print *,ddot(n,d1,1,d2,1)
> > end
> >
> > Compiling
> > R CMD SHLIB test.f
>
> Mmh, FORTRAN77 does not have dynamical memory allocation (though I have
> been told that many compilers implement it as an extension to the
> standard). So I am surprised that this code works. It is certainly
> not portable (i.e. a compiler that implements the FORTRAN77 standard
> strictly would barf on this code).
>
> Also, output to * in FORTRAN code dynamically linked to R is
> discouraged, see chapter 5.7 (Fortran I/O) in the "Writing R Extension"
> manual. From memory, many years ago one could do so (on linux and
> SUN machines atleast), then it stopped working. I am surprised that it
> works again.
>
> But neither of these two issues are the reason for your strange
> results. You would have pinpointed your actual problem easily if you
> would have used my favourite none-FORTRAN77 feature (which is
> implemented by most compilers as an extension), namely having "implicit
> none" as the first line in each function/subroutine. (The FORTRAN77
> compliant version, AFAIK, was to write "IMPLICIT CHARACTER (A-Z)" into
> the first line of all functions/subroutines.)
>
> Essentially, your routine testddot does not know what kind of result
> ddot returns and by the implicit type definition rules of FORTRAN77 it
> expects an INTEGER back. The fact that a DOUBLE PRECISION value is
> returned when an INTEGER is expected creates some confusion. Somewhere
> at the start of your routine you have to add a "DOUBLE PRECISION ddot"
> statement.
>
> HTH.
>
> Cheers,
>
> Berwin
>
> ========================== Full address ============================
> A/Prof Berwin A Turlach Tel.: +61 (8) 6488 3338 (secr)
> School of Maths and Stats (M019) +61 (8) 6488 3383 (self)
> The University of Western Australia FAX : +61 (8) 6488 1028
> 35 Stirling Highway
> Crawley WA 6009 e-mail: berwin.turl...@gmail.com
> Australia http://www.maths.uwa.edu.au/~berwin
> http://www.researcherid.com/rid/A-4995-2008
>
[[alternative HTML version deleted]]
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
