Re: [Yade-users] [Question #253257]: generate a random number in the C++ code
Question #253257 on Yade changed: https://answers.launchpad.net/yade/+question/253257 Raphaël Maurin posted a new comment: Thank you for your replies. I just had a quick look at a review about random number generator in the chapter 7 of [1]. It is very interesting, and well detailed. They underline the fact that some usual generator proposed can be pretty bad, because the parametrization of the generators can be very important for the randomness. In my case, the random number generation is important but not crucial so I am not looking for something perfect but good enough. It seems that the linear congruential generators, as the one you use Klaus are adapted to my use. The parametrization the generators minstd_rand0 proposed in boost library (variation of the one you are using : minstd_rand) is based on the parametrization proposed by Park and Miller, which is cited as an efficient parametrization by [1]. It is described as a a good minimal standard random number generator. For people interested in more efficient generator, I think it is worth having a look at [1]. One last question Klaus, how did you test the random number generator exactly ? Thank you all for the help ! Raphaël [1] p.274 Numerical Recipes in C: The Art of Scientific Computing, Second Edition, William H. Press, Brian P. Flannery, Saul A. Teukolsky, William T. Vetterling. (1992) http://www2.units.it/ipl/students_area/imm2/files/Numerical_Recipes.pdf -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #253257]: generate a random number in the C++ code
Question #253257 on Yade changed: https://answers.launchpad.net/yade/+question/253257 Klaus Thoeni posted a new comment: Hi, as far as I remember I did some simple tests by generating several set of numbers using different number generators and seed numbers. Then I did some simple statistics for each set in order to check their distributions. HTH Klaus -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
[Yade-users] [Question #253257]: generate a random number in the C++ code
New question #253257 on Yade: https://answers.launchpad.net/yade/+question/253257 Hi all, I need to generate a random number from a gaussian distribution in the C++ code of Yade. For that, basing myself on http://www.cplusplus.com/reference/random/normal_distribution/ I wrote in the cpp file : #includerandom std::default_random_engine generator; std::normal_distributiondouble distribution(0.0,1.0); double number = distribution(generator); When compiling, I get an error which I do not understand : In file included from /usr/include/c++/4.6/random:35:0, from /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:13: /usr/include/c++/4.6/bits/c++0x_warning.h:32:2: erreur: #error This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options. /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp: In member function ‘virtual void HydroForceEngine::action()’: /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:94:3: erreur: ‘default_random_engine’ is not a member of ‘std’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:94:30: erreur: expected ‘;’ before ‘generator’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:95:3: erreur: ‘normal_distribution’ is not a member of ‘std’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:95:28: erreur: expected primary-expression before ‘double’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:95:28: erreur: expected ‘;’ before ‘double’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:109:27: erreur: ‘generator’ was not declared in this scope /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:109:36: erreur: ‘distribution’ was not declared in this scope make[2]: *** [CMakeFiles/yade.dir/pkg/common/ForceEngine.cpp.o] Erreur 1 make[2]: *** Attente des tâches non terminées make[1]: *** [CMakeFiles/yade.dir/all] Erreur 2 make: *** [all] Erreur 2 Do you have an idea from where this error come from ? If necessary I can put the whole code but I don't think it will bring something. Raphaël -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #253257]: generate a random number in the C++ code
Hi, are you using the latest trunk version? There we have already enabled C++11, which you seems need for the compilation of this code. Cheers, Anton 2014-08-18 13:56 GMT+02:00 Raphaël Maurin question253...@answers.launchpad.net: New question #253257 on Yade: https://answers.launchpad.net/yade/+question/253257 Hi all, I need to generate a random number from a gaussian distribution in the C++ code of Yade. For that, basing myself on http://www.cplusplus.com/reference/random/normal_distribution/ I wrote in the cpp file : #includerandom std::default_random_engine generator; std::normal_distributiondouble distribution(0.0,1.0); double number = distribution(generator); When compiling, I get an error which I do not understand : In file included from /usr/include/c++/4.6/random:35:0, from /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:13: /usr/include/c++/4.6/bits/c++0x_warning.h:32:2: erreur: #error This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options. /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp: In member function ‘virtual void HydroForceEngine::action()’: /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:94:3: erreur: ‘default_random_engine’ is not a member of ‘std’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:94:30: erreur: expected ‘;’ before ‘generator’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:95:3: erreur: ‘normal_distribution’ is not a member of ‘std’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:95:28: erreur: expected primary-expression before ‘double’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:95:28: erreur: expected ‘;’ before ‘double’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:109:27: erreur: ‘generator’ was not declared in this scope /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:109:36: erreur: ‘distribution’ was not declared in this scope make[2]: *** [CMakeFiles/yade.dir/pkg/common/ForceEngine.cpp.o] Erreur 1 make[2]: *** Attente des tâches non terminées make[1]: *** [CMakeFiles/yade.dir/all] Erreur 2 make: *** [all] Erreur 2 Do you have an idea from where this error come from ? If necessary I can put the whole code but I don't think it will bring something. Raphaël -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #253257]: generate a random number in the C++ code
Question #253257 on Yade changed: https://answers.launchpad.net/yade/+question/253257 Status: Open = Answered Anton Gladky proposed the following answer: Hi, are you using the latest trunk version? There we have already enabled C++11, which you seems need for the compilation of this code. Cheers, Anton 2014-08-18 13:56 GMT+02:00 Raphaël Maurin question253...@answers.launchpad.net: New question #253257 on Yade: https://answers.launchpad.net/yade/+question/253257 Hi all, I need to generate a random number from a gaussian distribution in the C++ code of Yade. For that, basing myself on http://www.cplusplus.com/reference/random/normal_distribution/ I wrote in the cpp file : #includerandom std::default_random_engine generator; std::normal_distributiondouble distribution(0.0,1.0); double number = distribution(generator); When compiling, I get an error which I do not understand : In file included from /usr/include/c++/4.6/random:35:0, from /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:13: /usr/include/c++/4.6/bits/c++0x_warning.h:32:2: erreur: #error This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options. /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp: In member function ‘virtual void HydroForceEngine::action()’: /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:94:3: erreur: ‘default_random_engine’ is not a member of ‘std’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:94:30: erreur: expected ‘;’ before ‘generator’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:95:3: erreur: ‘normal_distribution’ is not a member of ‘std’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:95:28: erreur: expected primary-expression before ‘double’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:95:28: erreur: expected ‘;’ before ‘double’ /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:109:27: erreur: ‘generator’ was not declared in this scope /home/raphael/these/code/Yade/trunk/pkg/common/ForceEngine.cpp:109:36: erreur: ‘distribution’ was not declared in this scope make[2]: *** [CMakeFiles/yade.dir/pkg/common/ForceEngine.cpp.o] Erreur 1 make[2]: *** Attente des tâches non terminées make[1]: *** [CMakeFiles/yade.dir/all] Erreur 2 make: *** [all] Erreur 2 Do you have an idea from where this error come from ? If necessary I can put the whole code but I don't think it will bring something. Raphaël -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #253257]: generate a random number in the C++ code
Question #253257 on Yade changed: https://answers.launchpad.net/yade/+question/253257 Status: Answered = Solved Raphaël Maurin confirmed that the question is solved: Hi Anton, I was using the 29/06/2014 version, I updated and it solved the problem. Thank you ! Raphaël -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #253257]: generate a random number in the C++ code
Question #253257 on Yade changed: https://answers.launchpad.net/yade/+question/253257 Raphaël Maurin confirmed that the question is solved: Thanks Anton Gladky, that solved my question. -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #253257]: generate a random number in the C++ code
Question #253257 on Yade changed: https://answers.launchpad.net/yade/+question/253257 Raphaël Maurin posted a new comment: One last thing, the random number generator using #includerandom std::default_random_engine generator; std::normal_distributiondouble distribution(0.0,1.0); double number = distribution(generator); is pretty bad, I am able to see by eyes some number which are repeated many times...I don't like it much. Does someone knows a better way to generate random numbers in C++ ? Thanks ! Raphaël -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #253257]: generate a random number in the C++ code
Question #253257 on Yade changed:
https://answers.launchpad.net/yade/+question/253257
Jan Stránský posted a new comment:
Hi Raphael,
to generate random number in the interval 0 to 1, I use
double random() { return (double)rand()/(double)RAND_MAX; }
for normal distribution I use Box-Muller method (see also [1,2])
// function generating normally distributed random numbers using Box-Muller
method
double randNormal (double mean, double stddev, double min=-1e200, double
max=1e200) {
double r, u, v, c, ret;
do {
do {
u = 2*(double)rand() / (double)RAND_MAX-1;
v = 2*(double)rand() / (double)RAND_MAX-1;
r = u*u + v*v;
} while (r==0. || r1.);
c = sqrt(-2*log(r)/r);
ret = mean + u*c*stddev;
} while (ret = min || ret = max);
return ret;
}
cheers
Jan
[1] http://en.wikipedia.org/wiki/Box%E2%80%93Muller_transform
[2]
http://math60082.blogspot.cz/2013/03/c-coding-random-numbers-and-monte-carlo.html
2014-08-18 19:36 GMT+02:00 Raphaël Maurin
question253...@answers.launchpad.net:
Question #253257 on Yade changed:
https://answers.launchpad.net/yade/+question/253257
Raphaël Maurin posted a new comment:
One last thing, the random number generator using
#includerandom
std::default_random_engine generator;
std::normal_distributiondouble distribution(0.0,1.0);
double number = distribution(generator);
is pretty bad, I am able to see by eyes some number which are repeated
many times...I don't like it much. Does someone knows a better way to
generate random numbers in C++ ?
Thanks !
Raphaël
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Re: [Yade-users] [Question #253257]: generate a random number in the C++ code
Question #253257 on Yade changed: https://answers.launchpad.net/yade/+question/253257 Bruno Chareyre posted a new comment: I suspect the problem is in the generator, not in the distribution. In other words, Box-Muller based on std::default_random_engine would be bad as well. I guess you have seen the list of available generators [1]. Not sure which one is best but, for the one you tried it says: provides at least acceptable engine behavior for relatively casual, inexpert, and/or lightweight use... I have no idea what is used for std::rand(). It seems it is implementation dependent. It could be a wrapper of std::default_random_engine... [1] http://www.cplusplus.com/reference/random/ -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
Re: [Yade-users] [Question #253257]: generate a random number in the C++ code
Question #253257 on Yade changed: https://answers.launchpad.net/yade/+question/253257 Klaus Thoeni posted a new comment: Hi, I am using boost's random number generators. I tested them and I am very happy. Have a look in the code [1] and here [2]. Cheers, Klaus [1] https://github.com/yade/trunk/blob/master/pkg/dem/WirePM.cpp [2] http://www.boost.org/doc/libs/1_55_0/doc/html/boost_random.html -- You received this question notification because you are a member of yade-users, which is an answer contact for Yade. ___ Mailing list: https://launchpad.net/~yade-users Post to : yade-users@lists.launchpad.net Unsubscribe : https://launchpad.net/~yade-users More help : https://help.launchpad.net/ListHelp
