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Carsten Gräser authored
`Dune::Timer` includes two alternative implementations
for measuring time. Historically one was based on `getrusage()`
and the other one on `std::clock()`. The former was the default
and the latter could be enabled by defining a macro. Both in fact
measured the time spend computing by the process.

In `fa43f4bf` the default code path was changed from
`getrusage()` to `std::chrono::high_resolution_clock::now()`
while `std::clock()` could still be enabled by the macro.
This was in fact a breaking change because the new default
version measures the elapsed real time.

This patch removed the non-default version based on `std::clock` because:

* The breaking change happened almost 11 years so one can consider the
  new behavior the established 'correct' version.
* The macro switch was neither documented nor tested.
* Setting the macro manually in user code is error prone.
* Both versions do completely different things leading to
  different measurements. It's not even clear that one
  produces larger numbers in general:
  `std::clock` adds up time spend computing in all threads of the
  process. Thus time in concurrent threads is added up, while
  the time a thread is sleeping is not counted.

There a minor grain of salt: The documentation still documented
the old behaviour and instead of 'fixing' the code this patch
adjusts the documentation to established reality.
5b13e205
History

DUNE-library

DUNE, the Distributed and Unified Numerics Environment is a modular toolbox for solving partial differential equations with grid-based methods.

The main intention is to create slim interfaces allowing an efficient use of legacy and/or new libraries. Using C++ techniques DUNE allows one to use very different implementation of the same concept (i.e. grid, solver, ...) under a common interface with a very low overhead.

DUNE was designed with flexibility in mind. It supports easy discretization using methods, like Finite Elements, Finite Volume and also Finite Differences. Through separation of data structures DUNE allows fast Linear Algebra like provided in the ISTL module, or usage of external libraries like BLAS.

This package contains the basic DUNE common classes.

Dependencies

dune-common depends on the following software packages

  • CMake >= 3.16
  • Compiler (C, C++): GNU >= 10 or Clang >= 13
  • Library: GNU libstdc++ >= 10 or Clang libc++ >= 13

Other compilers may also work, but they must support C++20 to the same extent as the above. For an overview of the C++20 features supported by these versions, see https://en.cppreference.com/w/cpp/compiler_support. For compiling the Python bindings, libc++ is not currently supported.

The following software is recommended but optional:

  • pkg-config
  • MPI (either OpenMPI, lam, or mpich suffice)
  • Python >= 3.7 (interpreter and development kit for building the python bindings)

For a full explanation of the DUNE installation process please read the installation notes. The following introduction is meant for the impatient.

License

The DUNE-library and headers are licensed under version 2 of the GNU General Public License, with the so-called "runtime exception", as follows:

As a special exception, you may use the DUNE source files as part of a software library or application without restriction. Specifically, if other files instantiate templates or use macros or inline functions from one or more of the DUNE source files, or you compile one or more of the DUNE source files and link them with other files to produce an executable, this does not by itself cause the resulting executable to be covered by the GNU General Public License. This exception does not however invalidate any other reasons why the executable file might be covered by the GNU General Public License.

This license clones the one of the libstdc++ library. For further implications of this library please see their license page

See the file COPYING for full copying permissions.

Installation

Short installation instructions can be found in file INSTALL. For the full instructions please see here.

Links

  1. https://www.dune-project.org/installation/installation-faq/
  2. https://dune-project.org/releases/
  3. https://dune-project.org/doc/buildsystem/
  4. https://gcc.gnu.org/onlinedocs/libstdc++/faq.html#faq.license