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
Thread 0 Crashed:
0 libSystem.B.dylib 0x9341bb9e __kill + 10
1 libSystem.B.dylib 0x93492ec2 raise + 26
2 libSystem.B.dylib 0x934a247f abort + 73
3 randtoolbox.so 0x15e65f1d 0x15e5d000 + 36637
4 randtoolbox.so 0x15e614ef fill_array32 + 4038
5 randtoolbox.so 0x15e6513d SFmersennetwister + 335
6 randtoolbox.so 0x15e652c6 doSFMersenneTwister + 255
7 libR.dylib 0x00367a52 do_dotcall + 1394
8 libR.dylib 0x0038b5a2 Rf_eval + 1754
9 libR.dylib 0x0038f9a2 do_set + 592
10 libR.dylib 0x0038b366 Rf_eval + 1182
11 libR.dylib 0x0038b366 Rf_eval + 1182
12 libR.dylib 0x0038c140 do_begin + 58
13 libR.dylib 0x0038b366 Rf_eval + 1182
14 libR.dylib 0x0038b366 Rf_eval + 1182
15 libR.dylib 0x0038c140 do_begin + 58
16 libR.dylib 0x0038b366 Rf_eval + 1182
17 libR.dylib 0x0038d9a6 Rf_applyClosure + 663
18 libR.dylib 0x0038b25d Rf_eval + 917
19 org.R-project.R 0x000189c3 run_REngineRmainloop + 569
(Rinit.m:442)
20 org.R-project.R 0x0001142a -[REngine runREPL] + 260
(REngine.m:181)
21 org.R-project.R 0x00002e91 main + 795 (main.m:126)
22 org.R-project.R 0x00002b5a _start + 216
23 org.R-project.R 0x00002a81 start + 41
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