Thanks for your remarks. According to http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/SFMT/howto-compile.html, I need 16 bit aligned memory when using fill_array64. So I suppose I need 8 bit aligned memory. I will test what you advise me and will come back to R-devel list after.
Thanks again Christophe 2008/8/13 Prof Brian Ripley <[EMAIL PROTECTED]> > On Tue, 12 Aug 2008, Jeffrey Horner wrote: > > Christophe Dutang1 wrote: >> >>> Hi, >>> >>> I'm currently R porting SF Mersenne Twister algorithm of Matsumoto and >>> Saito. To get the full power of their code, I want to use their fonction >>> fill_array32 which need aligned memory. That is to say I need to use the C >>> function memalign on windows, posix_memalign on linux and classic malloc on >>> Mac OS. In 'writing R extenstion', they recommand to use R_alloc function to >>> allocate memory in C. >>> >>> Does R_alloc return a pointer to aligned memory? >>> if not how can I do this? >>> probably no, because R crashes when I succesively R_alloc and >>> fill_array32 (cf below) on my macbook with R 2.7.1. >>> >> >> You can still do this. Just take the address returned from R_alloc and >> test for alignment. If it's not, then just use an aligned address beyond the >> one returned. >> > > We haven't been told what the desired alignment is (and those functions > need to be told). On 32-bit Mac OS X, R_alloc is definitely aligned on > 4-byte boundaries (on 64-bit OSes it is usually 8-byte aligned). > > (But then the question is, which direction beyond the one returned? How >> does one test for that?) >> > > Addresses always go upwards. So if you want 64-byte alignment you need to > allocate a block at least 64 bytes longer than required, and go up to the > nearest multiple of 64. > > BTW, this is clearly an R-devel question -- see the posting guide. > > > >> Jeff >> >> Thanks in advance >>> >>> Kind regards >>> >>> Christophe >>> >>> >>> PS : >>> http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/SFMT/howto-compile.html<http://www.math.sci.hiroshima-u.ac.jp/%7Em-mat/MT/SFMT/howto-compile.html>provides >>> an example of memalign. >>> >>> PPS : mac os report >>> >> > [removed] > > -- > Brian D. Ripley, [EMAIL PROTECTED] > Professor of Applied Statistics, > http://www.stats.ox.ac.uk/~ripley/<http://www.stats.ox.ac.uk/%7Eripley/> > University of Oxford, Tel: +44 1865 272861 (self) > 1 South Parks Road, +44 1865 272866 (PA) > Oxford OX1 3TG, UK Fax: +44 1865 272595 > [[alternative HTML version deleted]] ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
