Dealii 9.2.0 has compilation errors under Windows when using PETSC and SLEPC support.

[loylick]

Hi guys! It has been a while since I compiled Dealii last time. I guess this error is seldom to come by because a few would engage in compiling Dealii for naitive Windows with PETSC and SLEPC.
The cmake command I used to configure Dealii is:
cmake -G "Visual Studio 15 2017 Win64" -DPETSC_DIR=h:/dev/petsc-3.13.2 -DPETSC_ARCH="arch-mswin-c-release" -DSLEPC_DIR=h:/dev/slepc-3.13.3 -DSLEPC_ARCH="arch-mswin-c-release" -DDEAL_II_WITH_UMFPACK=ON -DLAPACK_FOUND=true -DLAPACK_LIBRARIES="h:/Dev/petsc-3.13.2/arch-mswin-c-release/lib/libf2clapack.lib;h:/Dev/petsc-3.13.2/arch-mswin-c-release/lib/libf2cblas.lib" -DLAPACK_LINKER_FLAGS="-lm" ..
Otherwise I could not persuade dealii to find clapack and cblas packges intalled with PETSC.
Here are the errors I got:

Actually It is only one error in the line friend class SolverBase. The compiler finds some template class dealii:SolverBase and complains why I did not provide template arguments when referring to this class. I think this issue will appear not only under windows because the class dealii::SLEPcWrappers::SolverBase is not declared elsewhere in the file dealii-9.2.0\include\deal.II\lac\slepc_spectral_transformation.h. I've resolved this error by a forward declaration of the class SolverBase within the namespce SLEPcWrappers. Here is my patch:
patch.txt

[loylick]

Forgot to add that besides this error everything went smooth. I've succeeded in compiling the whole project in Debug and Release. My respect to Dealii team!

[bangerth]

That's by and large pretty good news indeed! I think it is mostly due to the fact that we now have a few industry projects using deal.II on windows, and that makes sure that stuff is compiled regularly.

Do you know how to make your patch into a pull request? (If not, take a look here: https://github.com/dealii/dealii/wiki/Contributing .) It would be nice to get a pull request because then you're the actual and official author in the git history. But if you want, we can also take your patch and apply it ourselves -- just let us know!

[loylick]

Hi Wolfgang! A couple of years ago I made two or three pool requests and had already officially contributed to dealii. Now, it is just a line of code. I would rather ask you to apply the patch. For you, it will take a few minutes. I do not have all this kitchen on the run so it would take me an hour or so to accomplish the pool request.

[bangerth]

I would have gladly done it, but @masterleinad beat me to it :-)