Using PetscWrappers::TimeStepper with LinearAlgebra::distributed::Vector

[Praveen C]

Hello

In a time explicit DG code, I am trying to use petsc timerstepper. But it looks like it does not work with LinearAlgebra::distributed::Vector

Is this not supported, or it is not possible to support this vector type ?

Thanks
praveen

Here is the compile time error, when I use docker dealii/dealii:latest

dealii@2ea11578dc08:~/shared/dg2d/system_lagrange_mpi$ make
[ 50%] Building CXX object CMakeFiles/main.dir/main.cc.o
[100%] Linking CXX executable main
/home/dealii/shared/dg2d/system_lagrange_mpi/dg.h:876: error: undefined reference to 'dealii::PETScWrappers::TimeStepper<dealii::LinearAlgebra::distributed::Vector<double, dealii::MemorySpace::Host>, dealii::PETScWrappers::MatrixBase, dealii::PETScWrappers::MatrixBase>::TimeStepper(dealii::PETScWrappers::TimeStepperData const&, ompi_communicator_t*)'
/home/dealii/shared/dg2d/system_lagrange_mpi/dg.h:877: error: undefined reference to 'dealii::PETScWrappers::TimeStepper<dealii::LinearAlgebra::distributed::Vector<double, dealii::MemorySpace::Host>, dealii::PETScWrappers::MatrixBase, dealii::PETScWrappers::MatrixBase>::petsc_ts()'
/home/dealii/shared/dg2d/system_lagrange_mpi/dg.h:878: error: undefined reference to 'dealii::PETScWrappers::TimeStepper<dealii::LinearAlgebra::distributed::Vector<double, dealii::MemorySpace::Host>, dealii::PETScWrappers::MatrixBase, dealii::PETScWrappers::MatrixBase>::petsc_ts()'
/home/dealii/shared/dg2d/system_lagrange_mpi/dg.h:910: error: undefined reference to 'dealii::PETScWrappers::TimeStepper<dealii::LinearAlgebra::distributed::Vector<double, dealii::MemorySpace::Host>, dealii::PETScWrappers::MatrixBase, dealii::PETScWrappers::MatrixBase>::solve(dealii::LinearAlgebra::distributed::Vector<double, dealii::MemorySpace::Host>&)'
/home/dealii/shared/dg2d/system_lagrange_mpi/dg.h:911: error: undefined reference to 'dealii::PETScWrappers::TimeStepper<dealii::LinearAlgebra::distributed::Vector<double, dealii::MemorySpace::Host>, dealii::PETScWrappers::MatrixBase, dealii::PETScWrappers::MatrixBase>::~TimeStepper()'
/home/dealii/shared/dg2d/system_lagrange_mpi/dg.h:911: error: undefined reference to 'dealii::PETScWrappers::TimeStepper<dealii::LinearAlgebra::distributed::Vector<double, dealii::MemorySpace::Host>, dealii::PETScWrappers::MatrixBase, dealii::PETScWrappers::MatrixBase>::~TimeStepper()'
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/main.dir/build.make:411: main] Error 1
make[1]: *** [CMakeFiles/Makefile2:90: CMakeFiles/main.dir/all] Error 2
make: *** [Makefile:91: all] Error 2

[Marc Fehling]

Hi Praveen,

PETScWrappers::TimeStepper has only been explicitly instantiated for the PETScWrappers Vectors:
https://github.com/dealii/dealii/blob/25495718f4bb6aa45a8f6c8cc4f2aedbe8d62231/source/lac/petsc_ts.cc#L82-L89

Will deal.II compile if you add the corresponding instantiations for the LinearAlgebra Vectors?

Best,

Marc

[Praveen C]

Hello Marc

The documentation says

https://dealii.org/current/doxygen/deal.II/classPETScWrappers_1_1TimeStepper.html

VectorType must provide a petsc_vector() function but the LA distributed vector does not seem to have this, right ?

best

praveen

[Wolfgang Bangerth]

On 10/2/24 08:17, Praveen C wrote:
>
> The documentation says
>
> https://dealii.org/current/doxygen/deal.II/classPETScWrappers_1_1TimeStepper.html
>
> VectorType must provide a petsc_vector() function but the LA distributed
> vector does not seem to have this, right ?

In C++20 we actually check which vector classes are allowed:
https://github.com/dealii/dealii/blob/25495718f4bb6aa45a8f6c8cc4f2aedbe8d62231/include/deal.II/lac/petsc_ts.h#L326-L338
In short, you really can only use PETSc vectors (not even block vectors).

You could try the SUNDIALS wrappers. They are more flexible and allow
you to use any kind of vector type.

Best
W.