Announcing deal.II 9.6

[Wolfgang Bangerth]

Slightly delayed, but still worth announcing:

Version 9.6.0 of deal.II, the object-oriented finite element library
awarded the
J. H. Wilkinson Prize for Numerical Software, has been released. It is
available for free under an Open Source license from the deal.II homepage at

https://www.dealii.org/

The major changes of this release are:
- There are six new tutorial programs, on checkpointing simulations
(step-83), integrating time-dependent solvers with external time
stepping libraries (step-86, using PETSc's TS library), advanced
point evaluation techniques (step-87), non-matching grids
(step-89), and trace-based methods for PDEs on embedded surfaces
(step-90).
- Much work has gone into writing wrappers for Trilinos' Tpetra
stack of linear algebra classes. Tpetra is Trilinos' Kokkos-based
replacement for the now-deprecated Epetra stack. While many things
already work with the Tpetra wrappers, not everything that is
currently available with the Epetra wrappers is implemented with
the Tpetra wrappers at this point.
- Substantial improvements to the multigrid two-level transfer
operators, including matrix-free based versions and versions for
p-refinement.
- Strategies for better refinement of tetrahedra.
- Support for hanging nodes in the Nedelec-SZ implementation.
- Cubic simplex elements.
- Better and delayed orthogonalization strategies for the GMRES and
F-GMRES implementations.
- A class FERemoteEvaluation that provides support for evaluating
finite element shape functions and solutions on parts of the
domain stored by other MPI processes.
- Tool classes TaskResult and Lazy that provide ways to compute
values on a separate thread or only when first accessed.
- deal.II now requires and uses of C++17.

For more information see:
- The preprint at https://www.dealii.org/deal96-preprint.pdf
- The list of 185 changes listed at

https://www.dealii.org/developer/doxygen/deal.II/changes_between_9_5_2_and_9_6_0.html

The main features of deal.II are:
- Extensive documentation and 89 working example programs
- Support for dimension-independent programming
- Locally refined adaptive meshes and multigrid support
- A zoo of different finite elements
- Built-in support for shared memory and distributed parallel
computing, scaling from laptops to clusters with 300,000+ of
processor cores
- Interfaces to Trilinos, PETSc, SUNDIALS, UMFPACK and many other
external software packages
- Input and output for a wide variety of meshing and visualization
platforms.

The deal.II developers

[Wolfgang Bangerth]

All:
I have two follow-ups to the 9.6 announcement. This is the first:

To every deal.II release, many many people contribute. The release paper at
https://www.dealii.org/deal96-preprint.pdf
has 17 authors that have contributed in a major way to this release. It
also lists 38 others who have contributed patches, documentation, test
cases, and in other ways to this release:

Laryssa Abdala,
Mathias Anselmann,
Abbas Ballout,
Maximilian Bergbauer,
Julian Brotz,
Marco Feder,
Niklas Fehn,
Menno Fraters,
Quang Hoang,
Vladimir Ivannikov,
Tao Jin,
Yimin Jin,
Paras Kumar,
Sébastien Loriot,
Nils Much,
Abdullah Mujahid,
Bob Myhill,
Paul A. Patience,
Luz Paz,
Laura Prieto Saavedra,
Sebastian Proell,
Hendrik Ranocha,
Johannes Resch,
Andreas Ritthaler,
Malik Scheifinger,
David Schneider,
Richard Schussnig,
Nils Schween,
Kyle Schwiebert,
Simranjeet Singh,
Simon Sticko,
Dominik Still,
Thierry Thomas,
Vinayak Vijay,
Ivy Weber,
Simon Wiesheier,
Chengjiang Yin,
Stefano Zampini.

We are grateful for all of these contributions -- thank you! We could
not do all this without you all (in the list above, and on this mailing
list) as a community!

Best
Wolfgang

[Wolfgang Bangerth]

The other announcement about this release: There are numerous new
tutorial and code gallery programs in this release that are perhaps
interesting to some of you:

* step-83 demonstrates how one can implement checkpoint/restart
functionality in deal.II-based programs, using the BOOST serialization
functionality as a foundation. step-83 was written by Pasquale Africa,
Wolfgang Bangerth, and Bruno Blais using step-19 as its basis.

* step-86 is a program that solves the heat equation using PETSc's TS
(time stepping) framework for the solution of ordinary differential
equations. Written by Wolfgang Bangerth, Luca Heltai, and Stefano
Zampini (King Abdullah University of Science and Technology), it
illustrates how PDE solvers for time-dependent problems can be
integrated with existing ODE solver packages to use advanced ODE solver
concepts (such as higher-order time integration methods and adaptive
time step control), all without sacrificing the things that have
traditionally led code authors toward writing their own time stepping
routines (like wanting to change the mesh every once in a while, or
having to deal with boundary conditions).

* step-87 was contributed by Magdalena Schreter-Fleischhacker and Peter
Munch. It presents the advanced point-evaluation functionalities of
deal.II, which are useful for evaluating finite element solutions at
arbitrary points on meshes that can be distributed among processes. The
presented mini-examples are motivated by the application to two-phase
flow simulations and demonstrate, for example, the evaluation of
solution quantities at a surface mesh embedded in a background mesh, as
needed in the case in front-tracking.

* step-89 was contributed by Johannes Heinz (TU Wien), Maximilian
Bergbauer (Technical University of Munich), Marco Feder (SISSA), and
Peter Munch. It shows how to apply non-matching and/or Chimera methods
within matrix-free loops in deal.II.

* step-90 was contributed by Vladimir Yushutin (Clemson University) and
Timo Heister. It implements the trace finite element method (TraceFEM).
TraceFEM solves PDEs posed on a, possibly evolving, (dim-1)-dimensional
surface Gamma employing a fixed uniform background mesh of a
dim-dimensional domain in which the surface is embedded. Such surface
PDEs arise in problems involving material films with complex properties
and in other situations in which a non-trivial condition is imposed on
either a stationary or a moving interface. The program considers a
steady, complex, non-trivial surface and the prototypical
Laplace-Beltrami equation which is a counterpart of the Poisson problem
on flat domains.

In addition, there are three new programs in the code gallery (a
collection of user-contributed programs that often solve more
complicated problems than tutorial programs, and that are intended as
starting points for further research rather than as teaching tools):

* ``Crystal growth phase field model'', contributed by Umair Hussain;
* ``Nonlinear heat transfer problem'', contributed by Narasimhan
Swaminathan;
* ``Traveling-wave solutions of a qualitative model for combustion
waves'', contributed by Shamil Magomedov.