[Rd] floating point control on windows

[Prof Brian Ripley]

We recommend calling Rwin_fpset() which is exported by R.dll and is known
to do the trick.  As it contains

     _controlfp(_PC_64, _MCW_PC);

it may be that the args you used are incorrect (and I am not on Windows 
to check the docs, but note that is the form used in the URL you cite).

On Mon, 29 Aug 2005, Chris Paulse wrote:

> Hi,
>
> I'm sure that this question has come up many times before.  When I load an R
> extension dll I've built with the Microsoft compiler, I get the warning:

> Warning message:
>
> DLL attempted to change FPU control word from 8001f to 9001f
>
> So, what I did to try to fix the problem (to my knowledge, Microsoft will
> not support compile time switching of floating point control until version
> 8.0 of their compiler - see: http://blogs.msdn.com/ericflee) was to place
> the following statement inside R_init_mylib:

> _controlfp(_MCW_PC, _PC_64); // use extended precision for operations in x87
> FPU
>
> This didn't fix my problem.  I ended up sprinkling these liberally
> throughout my code, but that didn't help.  One thing I do like about the
> Microsoft compiler is the debugging facility.  But, I'll definitely switch
> to gcc if this is necessary to get rid of the problem.

-- 
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