R devel - May 2009 - using a "third party" DLL in my package

Hello all,

it seems my efforts in reading the manuals and help files aren't enough 
so here I am. The question is, how would I go about linking a 
pre-compiled DLL in to my package? I have previously successfully built 
packages with Fortran and C source code, but now I'd like to take this 
ready made DLL and call its routines from R.

My collegue was brave enough to simply try and put the DLL in src folder 
of the package and proceed with building and installing the same way as 
if it had been source code. And it works, on my computer and his. 
Clearly this isn't exactly portable, and while that's ok for the use we 
have in mind (we both work on Windows XP) I have a nagging feeling this 
is somehow criminal or unwise at least.

Why I want to do this might explain it a bit further but in fact the 
background contains another problem and I welcome anyone to give hints 
about that too.

So, we have some Fortran code from way back which deals with fitting 
taper curves for tree boles, and some other functions related to that. 
We wanted to make these available for use in R and I made a package with 
simple wrapper functions for the .Fortran calls, and built it with the 
help of the compiler in Rtools. All was fine until my collegue managed 
to bump in to a combination of parameters (tree species, height and 
breast height diameter) with which the computation freezes. We traced it 
to a certain very simple iteration in the Fortran code that finds the 
height at which the tree has a given diameter. I could give more details 
on that, but the point is that the very same computation goes through 
just fine when executed "fully" in Fortran, with the routines and an 
interface compiled with another Fortran compiler. And also when that 
compiler is used to make a DLL and that DLL is used within the R package 
in the way I described above.

In summary, what we seem to have here is a compiler dependent 
convergence problem. Possible solutions are to figure out what's wrong 
with the computation - and I've pretty much exhausted my skills on that 
- or to figure out how to use a working DLL, as was my first question.

Great big thanks in advance to anyone with advice!

Seija Sirki?,
senior researcher (statistics), Finnish forestry research institute

On Thu, 14 May 2009, Seija Sirki? wrote:
> Hello all,
>
> it seems my efforts in reading the manuals and help files aren't enough
so
> here I am. The question is, how would I go about linking a pre-compiled DLL
> in to my package? I have previously successfully built packages with
Fortran
> and C source code, but now I'd like to take this ready made DLL and
call its
> routines from R.
>
> My collegue was brave enough to simply try and put the DLL in src folder of
> the package and proceed with building and installing the same way as if it 
> had been source code. And it works, on my computer and his. Clearly this 
> isn't exactly portable, and while that's ok for the use we have in
mind (we
> both work on Windows XP) I have a nagging feeling this is somehow criminal
or
> unwise at least.
Unwise, since it is unsupported and might stop working at any time. 
Actually, you don't mention the version of R you used and (without 
checking) I think this may not work in all recent versions of R.

What you can so is to have an 'inst/libs' directory in your package 
sources, and put the DLL you want to use there.  Another approach 
(used in a few CRAN packages) is to use 'configure.win' to copy the 
DLL to a 'libs' directory in the installed package.  A third approach 
is to have a 'src/Makefile.win' that creates the DLL you want 
(possibly by just checking it is present in 'src', but also possiby by 
calling the mysterious Fortran compiler X you obliquely mention 
below).
> Why I want to do this might explain it a bit further but in fact the 
> background contains another problem and I welcome anyone to give hints
about
> that too.
>
> So, we have some Fortran code from way back which deals with fitting taper 
> curves for tree boles, and some other functions related to that. We wanted
to
> make these available for use in R and I made a package with simple wrapper 
> functions for the .Fortran calls, and built it with the help of the
compiler
> in Rtools. All was fine until my collegue managed to bump in to a
combination
> of parameters (tree species, height and breast height diameter) with which 
> the computation freezes. We traced it to a certain very simple iteration in
> the Fortran code that finds the height at which the tree has a given 
> diameter. I could give more details on that, but the point is that the very
> same computation goes through just fine when executed "fully" in
Fortran,
> with the routines and an interface compiled with another Fortran compiler. 
> And also when that compiler is used to make a DLL and that DLL is used
within
> the R package in the way I described above.
>
> In summary, what we seem to have here is a compiler dependent convergence 
> problem. Possible solutions are to figure out what's wrong with the 
> computation - and I've pretty much exhausted my skills on that - or to
figure
> out how to use a working DLL, as was my first question.
My concern would be that there are different cases that fail under 
Fortran compiler X and you are just sweeping the problem under the 
carpet.
>
> Great big thanks in advance to anyone with advice!
>
> Seija Sirki?,
> senior researcher (statistics), Finnish forestry research institute
-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595