[Rd] different results on linux and windows

[Kjell Konis]

Hi Klaus,

Why not just use R's random number generator? See section 6.3 of  
Writing R Extensions. It should give you the same sequence of  
pseudorandom numbers on all platforms.

HTH,
Kjell

On 12 mai 09, at 12:30, Klaus Nordhausen wrote:

> Dear R experts,
>
> we are preparing an R-package to compute the Oja Median which contains
> some C++ code in which random numbers are needed. To generate the  
> random
> numbers we use the following Mersenne-Twister implementation:
>
> // MersenneTwister.h
> // Mersenne Twister random number generator -- a C++ class MTRand
> // Based on code by Makoto Matsumoto, Takuji Nishimura, and Shawn  
> Cokus
> // Richard J. Wagner  v1.0  15 May 2003  rjwagner at writeme.com
>
> the random seed for the Mersenne-Twister is provided by our R-function
> which gives an (random) integer to  the C++ function srand() which in
> turn sets the seed in the code.
>
> Using the set.seed in R makes now the results reproducible, but the
> results differ between windows and linux.
>
> Does anyone know what the problem there is?
>
> Our suspicion is that the reason is that some libraries are different
> implemented on linux and windows (XP) compilers.
>
> After the program start we set the seed in row 447(vkm.cpp) with  
> srand(int);
>
> When the median will be calculated, an intern seed is set with  
> unsigned
>  int seed = rand();   ( in row 100 (vkm.cpp)). This seed will be used
> to calculate some random subsets and to
> create a Mersenne Twister object with MTRand rr(seed);  (row 156,  
> vkm.cpp).
>
> The MTRand Object rr is called with an unsigned Integer, so the
> important function in the mersenneTwister.h class is in line 87:
> MTRand( const uint32& oneSeed );
>
> According to that the Random Number Generator uses the methods
> initialize(oneSeed); and reload();  (inside the method, beginning in
> line 215)
>
> This both methods (line 283 and line 301) are using beside others
> registers. Could it be that there is a different behavior between
> Windows and Linux?
>
> We do not want to use only srand() since we might need more then the
> number of pseudo random numbers that algorithm can provide.
>
> For those interested and which would like to see the code, a first
> version of the package, called OjaMedian, is available as source file
> and windows binary on my homepage:
> http://www.uta.fi/~klaus.nordhausen/down.html
>
> The problem is in the ojaMedian function when the evolutionary  
> algorithm
> is used. Involved C++-files are mainly vkm.cpp and MersenneTwister.h.
>
> We would be very grateful for any advice on how to solve this problem.
> (below is also a demonstration)
>
> Thank you very much in advance,
>
> Klaus
>
> Results on windows XP:
>
> Compiler used: gcc version 4.2.1-sjlj (mingw32-2)
>
>> library(OjaMedian)
>> set.seed(1)
>> testD <- rmvnorm(20,c(0,0))
>> summary(testD)
>        V1                V2
>  Min.   :-2.2147   Min.   :-1.989352
>  1st Qu.:-0.3844   1st Qu.:-0.399466
>  Median : 0.3597   Median :-0.054967
>  Mean   : 0.1905   Mean   :-0.006472
>  3rd Qu.: 0.7590   3rd Qu.: 0.655663
>  Max.   : 1.5953   Max.   : 1.358680
>> set.seed(1)
>> ojaMedian(testD)
> [1]  0.21423705 -0.05799643
>> sessionInfo()
> R version 2.9.0 (2009-04-17)
> i386-pc-mingw32
>
> locale:
> LC_COLLATE=Finnish_Finland.1252;LC_CTYPE=Finnish_Finland. 
> 1252;LC_MONETARY=Finnish_Finland. 
> 1252;LC_NUMERIC=C;LC_TIME=Finnish_Finland.1252
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> other attached packages:
> [1] OjaMedian_0.0-14 ICSNP_1.0-3      ICS_1.2-1        survey_3.14
> [5] mvtnorm_0.9-5
>
> loaded via a namespace (and not attached):
> [1] tools_2.9.0
>>
>
> Results on Linux Kubuntu 8.10
> result of: cat /proc/version:
> Linux version 2.6.28-11-generic (buildd at palmer) (gcc version 4.3.3
> (Ubuntu 4.3.3-5ubuntu4) ) #42-Ubuntu SMP Fri Apr 17 01:57:59 UTC 2009
>
>> library(OjaMedian)
>> set.seed(1)
>> testD <- rmvnorm(20,c(0,0))
>> summary(testD)
>
>        V1                V2
>  Min.   :-2.2147   Min.   :-1.989352
>  1st Qu.:-0.3844   1st Qu.:-0.399466
>  Median : 0.3597   Median :-0.054967
>  Mean   : 0.1905   Mean   :-0.006472
>  3rd Qu.: 0.7590   3rd Qu.: 0.655663
>  Max.   : 1.5953   Max.   : 1.358680
>
>> set.seed(1)
>> ojaMedian(testD)
>
> (-0.501381, 0.193929)[1] 0.119149071 0.002732100
>
>> sessionInfo()
>
> R version 2.8.1 (2008-12-22)
> i486-pc-linux-gnu
>
> locale:
> LC_CTYPE 
> = 
> en_US 
> .UTF 
> -8 
> ;LC_NUMERIC 
> = 
> C 
> ;LC_TIME 
> = 
> en_US 
> .UTF 
> -8 
> ;LC_COLLATE 
> = 
> en_US 
> .UTF 
> -8 
> ;LC_MONETARY 
> = 
> C 
> ;LC_MESSAGES 
> = 
> en_US 
> .UTF 
> -8 
> ;LC_PAPER 
> = 
> en_US 
> .UTF 
> -8 
> ;LC_NAME 
> = 
> C 
> ;LC_ADDRESS 
> =C;LC_TELEPHONE=C;LC_MEASUREMENT=en_US.UTF-8;LC_IDENTIFICATION=C
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> other attached packages:
> [1] OjaMedian_0.0-14 ICSNP_1.0-3      ICS_1.2-1        survey_3.14
> [5] mvtnorm_0.9-5
>
>
>
>
>
> -- 
> Klaus Nordhausen
> Researcher
> Tampere School of Public Health
> FIN-33014 University of Tampere
>
> phone:	+358 3 3551 4153
> fax:	+358 3 3551 4150
> e-mail:	Klaus.Nordhausen at uta.fi
>
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