[fluidflowsteel]

Hi all,

I want to generate random numbers in OF 2.2.0 between -1 and +1 for the whole mesh initially which will remain same for all time steps. Can you advice how to do this ?


with regards,

[Tobi]

Simple task,

there is a class called Random. An example is in my Gray-Scott-Solver ... https://bitbucket.org/shor-ty/graysc...e-view-default

[jorkolino]

Originally Posted by Tobi

Simple task,

there is a class called Random. An example is in my Gray-Scott-Solver ... https://bitbucket.org/shor-ty/graysc...e-view-default

Do you know how to seed the random generator with arbitrary seed (for example CPU time clock) and not some fixed number, in your case '1'.

[Tobi]

Hi,

sure, you just define a variable that changes and then you give it as an argument to the class.

[Ramkumar21194]

Hi, is it possible to generate random list of "N" numbers between given range (a,b)? using that class? Like i need some 10 numbers between say 0 to 100.


And it gives following error when i run that script.

Test.C:13:40: error: ‘Foam::scalar Foam::Random::scalar01()’ is private within this context
const scalar randNumber(obj.scalar01());

[vitor.geraldes@ist.utl.pt]

#include <iostream>
#include "fvCFD.H"
#include "Random.H"
#include "Time.H"

int main ()
{

Random randObj(clock::getTime());
Info << randObj.scalar01()<< endl;

}

[Ramkumar21194]

Originally Posted by vitor.geraldes@ist.utl.pt

#include <iostream>
#include "fvCFD.H"
#include "Random.H"
#include "Time.H"

int main ()
{

Random randObj(clock::getTime());
Info << randObj.scalar01()<< endl;

}

i am getting following error when i use your code.

 testCode.C: In function ‘int main(int, char**)’:
testCode.C:50:29: error: ‘Foam::scalar Foam::Random::scalar01()’ is private within this context     Info << ranObj.scalar01();

[olesen]

Originally Posted by Ramkumar21194

i am getting following error when i use your code.

 testCode.C: In function ‘int main(int, char**)’:
testCode.C:50:29: error: ‘Foam::scalar Foam::Random::scalar01()’ is private within this context     Info << ranObj.scalar01();

The scalar01() was in older code, try with the general method instead:

Random rng;
rng.sample01<scalar>();

Note that depending on your version of OpenFOAM, you can also use the generator op for the same thing, or with a different range. This can then be used as a generator function for C++ algorithms. For example,

Random::uniformGeneratorOp<scalar> randVal(0,10);
scalarField fld(1000);

std::generate (fld.begin(), fld.end(), randVal);

//  the same, as a loop

for (scalar& val : fld)
{
    val = randVal();
}

It even has a unary form that ignores its argument, which you can use to "swallow" the argument and return a random value instead. Replace something like magOp<scalar>() with your generator etc.