[Rd] using a "third party" DLL in my package

Prof Brian Ripley ripley at stats.ox.ac.uk
Sun May 24 08:31:18 CEST 2009

It is likely that this is related to using higher-precision FPU 
registers, in which case there is a portable solution: look up 
SAFE_FFLAGS in 'Writing R Extensions'.

But if that is the cause, the real solution is to write the code using 
proper convergence tests.

On Sat, 23 May 2009, Kasper Daniel Hansen wrote:

> On May 20, 2009, at 4:32 , Seija Sirkiä wrote:
>> Hello again,
>> thank you for the comments, especially this one:
>> Prof Brian Ripley wrote:
>>> 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.
>> It inspired us to go back to search the cause, and we've made some 
>> progress: it's not the compiler, it's the compiler options. Simple, but it 
>> took a while to figure that out since my experience in these things is 
>> limited. When I build the package with default options using INSTALL 
>> --build the dll is built with option -O3 as per R's Makeconfig file. If I 
>> build the dll by hand, using gfortran with no additional options and 
>> dyn.load it, everything works, and also with -O and -Os. (No, I don't fully 
>> understand what the differences between all these are, but that's another 
>> question).
>> I'm looking at chapter 5.5 in Writing R Extensions and also 6.3.3 in R 
>> Installation and Administration but I can't figure out how to tell "inside" 
>> my package that it is not to be built -O3 but with, say, -O. I can see how 
>> to add flags in the package (and as far as I can tell, if there are several 
>> optimization level flags the last in line is used and that's the wrong one 
>> from my point of view), and also how to override flags but only on my 
>> computer. Am I blind or am I again attempting something I shouldn't?
> This is not trivial, and how you do it is compiler dependent. A quick fix was 
> provided by Simon Urbanek a while back and it is _not_ portable, it assumes 
> you are using GCC. It would be nice to have a configure file that detects the 
> compiler and optimization setting and then re-sets the optimization level. I 
> have thought about writing one, but have never got around to do it.
> Anyway, the fix is in the Makevars file from affxparser from Bioconductor. 
> Essentially, you use a Makevars file placed in the src directory, containing
> %.o: %.cpp
>       $(CXX) $(ALL_CPPFLAGS) $(ALL_CXXFLAGS) $(MYCXXFLAGS) -c $< -o $@
> Essentially this makes sure that -O0 (indicating no optimization) is placed 
> at the _end_ of the call to the compiler (this is for C++ files btw), using 
> the fact that if you have two -O* settings, the last one overrides the first.
> This ought to be easily adaptable to FORTRAN.
> Kasper
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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

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