Hi,
You are completely right, the problem was not about what R_alloc
returned but my use of the fill_array32. Now it works fine, but the
block generation is longer due to a conversion to double after using
fill_array32. I must underline the fact that I do not yet use sse2
support.
Thanks again
Christophe
Le 13 août 08 à 14:30, Luke Tierney a écrit :
On Wed, 13 Aug 2008, 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.
R_alloc's alignment will be appropriate for holding any data type. It
will be offset from a value returned by malloc by a multiple of 8
bytes.
My recollection, which may be wrong, is that on both Intel and PPC
unaligned access to all basic data types is permitted but may be
inefficient (in particular on Intel), so the reason for your crash is
probably elsewhere.
Best,
luke
Thanks in advance
Kind regards
Christophe
PS : http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/SFMT/howto-compile.html
provides an example of memalign.
PPS : mac os report
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