On 12-01-2014, at 08:26, 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. No. It is expecting ddot to return a REAL result (single precision). Berend > 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 > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
