[Yade-users] [Question #253249]: how to add Torque on a body
New question #253249 on Yade: https://answers.launchpad.net/yade/+question/253249 Hi, I want to directly add force and torque to some bodies ( for example 10 spheres ), and I find that there is a method called "addForce" to deal with the force. But is there any good way to add the torque conveniently ? Thanks for any of your suggestions! -- 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 #253059]: friction and shear stress
Question #253059 on Yade changed: https://answers.launchpad.net/yade/+question/253059 Jérôme Duriez posted a new comment: Hello, As a first advice, do you understand what is this "shear stress" you are speaking about ? (me not, but I think that would be the first step for you to understand your results) Jérôme -- 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 #253249]: how to add Torque on a body
Question #253249 on Yade changed: https://answers.launchpad.net/yade/+question/253249 Donia Marzougui proposed the following answer: Hi, It is the same for the force. you have just to write: forces.addTorque Bests Donia -- 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 #253249]: how to add Torque on a body
Question #253249 on Yade changed: https://answers.launchpad.net/yade/+question/253249 Status: Open => Answered Jan Stránský proposed the following answer: Hi Carrie addT is what you are looking for [1] cheers Jan [1] https://yade-dem.org/doc/yade.wrapper.html#yade.wrapper.ForceContainer.addT 2014-08-18 10:42 GMT+02:00 Carrie : > New question #253249 on Yade: > https://answers.launchpad.net/yade/+question/253249 > > Hi, > > I want to directly add force and torque to some bodies ( for example 10 > spheres ), and I find that there is a method called "addForce" to deal > with the force. But is there any good way to add the torque conveniently ? > > Thanks for any of your suggestions! > > -- > 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 #253105]: How to visualize bonds/cohesion using intr recorder and Paraview?
Question #253105 on Yade changed: https://answers.launchpad.net/yade/+question/253105 Status: Open => Answered Jérôme Duriez proposed the following answer: Hello, You're right that "intr" displays all interactions, so you probably need a model-specific recorder. For example, for another contact law, the "jcfpm" recorder (see [1]) allows to distinguish between cohesive- frictionnal and purely frictionnal interactions, using a JCFpmPhys variable [2]. You have to check if something similar exists in the "cpm" recorder, or you will have to implement it yourself. Jérôme [1] https://www.yade-dem.org/doc/yade.wrapper.html#yade.wrapper.VTKRecorder.recorders [2] https://www.yade-dem.org/doc/yade.wrapper.html#yade.wrapper.JCFpmPhys.isCohesive -- 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 #253249]: how to add Torque on a body
Question #253249 on Yade changed: https://answers.launchpad.net/yade/+question/253249 Carrie confirmed that the question is solved: Thanks Jan Stránský, 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 #253249]: how to add Torque on a body
Question #253249 on Yade changed: https://answers.launchpad.net/yade/+question/253249 Status: Answered => Solved Carrie confirmed that the question is solved: oh, I find a addT function... -- 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 : #include std::default_random_engine generator; std::normal_distribution 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 : > 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 : > #include > std::default_random_engine generator; > std::normal_distribution 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 : > 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 : > #include > std::default_random_engine generator; > std::normal_distribution 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 #253097]: Imposing constant velocity on clumps on single axis
Question #253097 on Yade changed: https://answers.launchpad.net/yade/+question/253097 Status: Answered => Solved Colin Power 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 #253097]: Imposing constant velocity on clumps on single axis
Question #253097 on Yade changed: https://answers.launchpad.net/yade/+question/253097 Colin Power posted a new comment: Just to add completeness to this question, this is what I changed in the function to get the desired result: def moreSpheres(i=1): y_shift = 0 for n in xrange(0,i): geoFile = 'ice_blocks/ice_block_'+str(random.randint(1,1000))+'.geo' y_shift+= random.uniform(10, 15) x_shift = random.uniform(0, 20) packing = yade.ymport.gengeoFile(fileName=geoFile, shift=Vector3(-99+x_shift, -99+y_shift, 2), scale=1.0, orientation=Quaternion((1, 0, 0), 0),color=sphereColor, material=ice, wire=False) clump = O.bodies.appendClumped(packing) clumpID = clump[0] O.bodies[clumpID].state.vel= Vector3(50,0,0) -- 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 #253105]: How to visualize bonds/cohesion using intr recorder and Paraview?
Question #253105 on Yade changed: https://answers.launchpad.net/yade/+question/253105 Status: Answered => Solved Colin Power confirmed that the question is solved: Thanks Jérôme Duriez, 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 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 #251218]: Modifying the Cohesive Frictional Contact Law
Question #251218 on Yade changed:
https://answers.launchpad.net/yade/+question/251218
Bruno Chareyre proposed the following answer:
I was away from keyboard. Sorry for slow reply Behzad.
I think you can keep the 3 variables of CohFrictPhys even if you don't need
them. It is harmless, and there is in fact a very good reason to keep them. If
later you or somebody else wants to combine the Burger model with contact
moments - and trust me it is likely to happen, it will be possible (for free!
no need to write new code).
Jan's suggestion to introduce an intermediate class is also good, but it does
not enable such combination of components.
I agree with Jan to delay the clean integration, just it is good to
anticipate it as it can guide the way you do the dirty tricks already.
As a simple example of how a good integration can look like,
Ip2_CohBurgersMat can inherit from Ip2_CohFrictMat so that:
void Ip2_CohBurgersMat_CohBurgersMat_CohBurgersPhys::go(b1,b2,i)
{
Ip2_CohFrictMat_CohFrictMat_CohFrictPhys::go(b1,b2,i); //here re-use
i->phys->kelvinViscosity = ... //here do the additional stuff
}
In this case you don't duplicate lines. If someone is fixing something
in Ip2_CohFrictMat_CohFrictMat_CohFrictPhys you will recieve the fix. If
you duplicate, the duplicated code will slowly diverge and bugs may
never be fixed.
Notes:
1/ This requires that you inherit from
2/ I don't see any kelvin/maxwell viscosity and stiffness in CohBurgersPhys at
the moment. I guess you will have to add something for some of them (not all,
since they can be partly covered by the inherited stiffness and viscosity
values).
3/ the example above can apply for Law2 functor as well (see [1]), but not
always. If you find that the burger model needs to insert lines in the middle
of the Law2::go() block of code (I mean if there is really no way to put all
new lines before or after the inherited go()) then we will need to think a bit
more.
I hope it helps
[1]
https://github.com/yade/trunk/blob/master/pkg/dem/ElasticContactLaw.cpp#L102
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Re: [Yade-users] [Question #252656]: Crash when using CPM model
Question #252656 on Yade changed: https://answers.launchpad.net/yade/+question/252656 Bruno Chareyre proposed the following answer: If some spheres have multiple contacts with facets, then maybe PWave timestep is irrelevant. Just an idea. If you want to be sure it is not a timestep problem you can use automatic timestep with GlobalStiffnessTimeStepper. Bruno -- 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 #253112]: memory leakage when passing a variable from python to C++
Question #253112 on Yade changed: https://answers.launchpad.net/yade/+question/253112 Bruno Chareyre proposed the following answer: Maybe python is just never erasing the vector that you pass from fortran to c++. I remember it can happen sometimes than python is not releasing memory as you expect. If this is the problem it will not be visible in the c++ code, and it will not be related to the bug mentionned by Anton. Can you show how you assign the values in the script? -- 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 #253112]: memory leakage when passing a variable from python to C++
Question #253112 on Yade changed: https://answers.launchpad.net/yade/+question/253112 Raphaël Maurin posted a new comment: Hi Bruno, To assign the value in the python script I write : HydroForceEngine.vxFluct = X X being the vector containing all the values of fluctuations which is the size of the number of bodies. 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 #253112]: memory leakage when passing a variable from python to C++
Question #253112 on Yade changed: https://answers.launchpad.net/yade/+question/253112 Bruno Chareyre requested more information: Now I see this (after [1]): HydroForceEngine.vxFluct = X Just a trivial thing: can you check len(HydroForceEngine.vxFluct) and len(X) just after this line? (to be sure) If sizes are correct, I will need to see more lines to imagine other things. [1] https://bugs.launchpad.net/yade/+bug/1041084 -- 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 #253112]: memory leakage when passing a variable from python to C++
Question #253112 on Yade changed: https://answers.launchpad.net/yade/+question/253112 Status: Answered => Open Raphaël Maurin is still having a problem: It gives always the same size which correspond to len(O.bodies) What else do you need ? Because you have the C++ source code above (cpp and hpp, one after the other) and I tried a very simplified script only executing the command HydroForceEngine.vxFluct = np.zeros(len(O.bodies) and I have the same problem. Raphael -- 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 #253112]: memory leakage when passing a variable from python to C++
Question #253112 on Yade changed: https://answers.launchpad.net/yade/+question/253112 Bruno Chareyre posted a new comment: This is how to reproduce your bug... for k in range(1000): e.ids=range(0,100) then watch yade eating the RAM... -- 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 #include std::default_random_engine generator; std::normal_distribution 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. || r>1.);
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
> #include
> std::default_random_engine generator;
> std::normal_distribution 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
