libMesh: A C++ Finite Element Library

Email Archive: libmesh-users (read-only)

[Libmesh-users] How to transfer a vector as parameters?

From: 蔡园武 <yuanwucai@gm...> - 2011-04-14 05:28

I have faced some problems in my code, and need your help.

1. I see that the user can pass parameters into equation_systems, so they
can be retrieved in other functions. But when I want to pass a vector or
matrix, it won't work:

    std::vector<Number> & EDA =
equation_systems.parameters.set<std::vector<Number> > ("ElemDensity");
    const unsigned int NElem = mesh.n_elem();
    EDA.resize(NElem);
    for (unsigned int i = 0; i < NElem; i++) {
        EDA[i] = 1.0;
        std::cout << EDA[i] << std::endl;
    }

Where am I wrong? How can I achieve my purpose?

2. I'm modeling a problem with multiple loadcases. I should solve the
system, save the solution; then change to another loadcase, solve the
system, and save again. All the saved solutions will be used later. But I
don't know how to save the solution in a vector? Will the following code
work?

    equation_systems.parameters.set<std::string> ("loadcase") = "11";
    system.solve();
    std::vector<Number> U11 = system.solution;
    system.matrix->zero();
    system.rhs->zero();
    system.solution->zero();
    equation_systems.parameters.set<std::string> ("loadcase") = "22";
    system.solve();
    std::vector<Number> U22 = system.solution;
    system.matrix->zero();
    system.rhs->zero();
    system.solution->zero();

where the system is a LinearImplicitSystem.

I'll be really appreciated for your answer, thanks at all!


-- 
Cai Yuanwu  蔡园武
Dept. of Engineering Mechanics,
Dalian University of Technology,
Dalian 116024, China

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Thread	Author	Date
[Libmesh-users] How to transfer a vector as parameters?	蔡园武 <yuanwucai@gm...>

Re: [Libmesh-users] How to transfer a vector as parameters?

From: John Peterson <peterson@cf...> - 2011-04-14 16:12

2011/4/13 蔡园武 <yuanwucai@...>:
> I have faced some problems in my code, and need your help.
>
> 1. I see that the user can pass parameters into equation_systems, so they
> can be retrieved in other functions. But when I want to pass a vector or
> matrix, it won't work:
>
>    std::vector<Number> & EDA =
> equation_systems.parameters.set<std::vector<Number> > ("ElemDensity");
>    const unsigned int NElem = mesh.n_elem();
>    EDA.resize(NElem);
>    for (unsigned int i = 0; i < NElem; i++) {
>        EDA[i] = 1.0;
>        std::cout << EDA[i] << std::endl;
>    }
>
> Where am I wrong? How can I achieve my purpose?

Are you seeing a compiler error or runtime error?  On my system,
attempting to put std::vectors into a Parameters object gives a
compile error:

in void libMesh::Parameters::Parameter<T>::print(std::ostream&)
parameters.h:280: error: no match for 'operator<<' in 'os <<(...)'

Since you can't print a vector this way.  This seems like an
unnecessary limitation on the Parameters class, we could possibly fix
it by specializing Parameter<T>::print(ostream&) for vector<T> but I
don't have the time to or any desire mess with that at the moment.

-- 
John

Re: [Libmesh-users] How to transfer a vector as parameters?

From: 蔡园武 <yuanwucai@gm...> - 2011-04-15 02:51

Thanks, John,
but I don't think it's just the print error, because if I comment the
std::cout sentence, the error message is the same. It seems that Parameters
only can hold basic values like int or Real, not the compound type like
vector.
If it is so, I must transfer the vector to other functions as an actual
parameter besides equation_systems and system_name.

2011/4/15 John Peterson <peterson@...>

> 2011/4/13 蔡园武 <yuanwucai@...>:
> > I have faced some problems in my code, and need your help.
> >
> > 1. I see that the user can pass parameters into equation_systems, so they
> > can be retrieved in other functions. But when I want to pass a vector or
> > matrix, it won't work:
> >
> >    std::vector<Number> & EDA =
> > equation_systems.parameters.set<std::vector<Number> > ("ElemDensity");
> >    const unsigned int NElem = mesh.n_elem();
> >    EDA.resize(NElem);
> >    for (unsigned int i = 0; i < NElem; i++) {
> >        EDA[i] = 1.0;
> >        std::cout << EDA[i] << std::endl;
> >    }
> >
> > Where am I wrong? How can I achieve my purpose?
>
> Are you seeing a compiler error or runtime error?  On my system,
> attempting to put std::vectors into a Parameters object gives a
> compile error:
>
> in void libMesh::Parameters::Parameter<T>::print(std::ostream&)
> parameters.h:280: error: no match for 'operator<<' in 'os <<(...)'
>
> Since you can't print a vector this way.  This seems like an
> unnecessary limitation on the Parameters class, we could possibly fix
> it by specializing Parameter<T>::print(ostream&) for vector<T> but I
> don't have the time to or any desire mess with that at the moment.
>
> --
> John
>



-- 
Cai Yuanwu  蔡园武
Dept. of Engineering Mechanics,
Dalian University of Technology,
Dalian 116024, China