[R] aligned memory allocation in C

[Christophe Dutang]

Yes, it seems a good idea but your two questions are also good  
questions!

Le 13 août 08 à 04:52, Jeffrey Horner a écrit :

> 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.
>
> (But then the question is, which direction beyond the one returned?  
> How does one test for that?)
>
> Jeff
>
>> 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
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
>
> -- 
> http://biostat.mc.vanderbilt.edu/JeffreyHorner