[web] Replace eigen links.

https://eigen.tuxfamily.org is down.
Use https://libeigen.gitlab.io/docs instead.

Documentation/ProjectFile/prj/linear_solvers/linear_solver/eigen/i_eigen.md

 Configuration for solvers from the Eigen library.
 
-For details see also the [documentation of the Eigen library](https://eigen.tuxfamily.org/dox/group__Sparse__Reference.html).
+For details see also the [documentation of the Eigen library](https://libeigen.gitlab.io/docs/group__Sparse__Reference.html).

Documentation/ProjectFile/prj/linear_solvers/linear_solver/eigen/t_angle.md

@@ -5,4 +5,4 @@ through OGS_USE_EIGEN_UNSUPPORTED CMake option.
 
 See following links for detail description:
 
-- "Detailed Description" in <https://eigen.tuxfamily.org/dox/unsupported/>
+- "Detailed Description" in <https://libeigen.gitlab.io/docs/unsupported/>

Documentation/ProjectFile/prj/linear_solvers/linear_solver/eigen/t_l.md

@@ -4,4 +4,4 @@ through OGS_USE_EIGEN_UNSUPPORTED CMake option.
 
 See following links for detail description:
 
-- "Detailed Description" in <https://eigen.tuxfamily.org/dox/unsupported/>
+- "Detailed Description" in <https://libeigen.gitlab.io/docs/unsupported/>

Documentation/ProjectFile/prj/linear_solvers/linear_solver/eigen/t_residual_update.md

@@ -5,4 +5,4 @@ through OGS_USE_EIGEN_UNSUPPORTED CMake option.
 
 See following links for detail description:
 
-- "Detailed Description" in <https://eigen.tuxfamily.org/dox/unsupported/>
+- "Detailed Description" in <https://libeigen.gitlab.io/docs/unsupported/>

Documentation/ProjectFile/prj/linear_solvers/linear_solver/eigen/t_restart.md

@@ -5,4 +5,4 @@ through OGS_USE_EIGEN_UNSUPPORTED CMake option.
 
 See following links for detail description:
 
-- "Detailed Description" in <https://eigen.tuxfamily.org/dox/unsupported/classEigen_1_1GMRES.html>
+- "Detailed Description" in <https://libeigen.gitlab.io/docs/unsupported/classEigen_1_1GMRES.html>

Documentation/ProjectFile/prj/linear_solvers/linear_solver/eigen/t_s.md

@@ -4,4 +4,4 @@ through OGS_USE_EIGEN_UNSUPPORTED CMake option.
 
 See following links for detail description:
 
-- "Detailed Description" in <https://eigen.tuxfamily.org/dox/unsupported/>
+- "Detailed Description" in <https://libeigen.gitlab.io/docs/unsupported/>

Documentation/ProjectFile/prj/linear_solvers/linear_solver/eigen/t_scaling.md

@@ -4,6 +4,6 @@ through OGS_USE_EIGEN_UNSUPPORTED CMake option.
 
 See following links for detail description:
 
-- "Note" in <https://eigen.tuxfamily.org/dox/classEigen_1_1SparseLU.html>
-- "Detailed Description" in <https://eigen.tuxfamily.org/dox/unsupported/namespaceEigen.html>
+- "Note" in <https://libeigen.gitlab.io/docs/classEigen_1_1SparseLU.html>
+- "Detailed Description" in <https://libeigen.gitlab.io/docs/unsupported/namespaceEigen.html>
 - References : D. Ruiz and B. Ucar, A Symmetry Preserving Algorithm for Matrix Scaling, INRIA Research report RR-7552

Documentation/ProjectFile/prj/linear_solvers/linear_solver/eigen/t_smoothing.md

@@ -4,4 +4,4 @@ through OGS_USE_EIGEN_UNSUPPORTED CMake option.
 
 See following links for detail description:
 
-- "Detailed Description" in <https://eigen.tuxfamily.org/dox/unsupported/>
+- "Detailed Description" in <https://libeigen.gitlab.io/docs/unsupported/>

MathLib/LinAlg/Eigen/EigenLinearSolver.cpp

@@ -259,7 +259,7 @@ public:
 
         // matrix must be copied, because Eigen's linear solver stores a
         // reference to it cf.
-        // https://eigen.tuxfamily.org/dox/classEigen_1_1IterativeSolverBase.html#a7dfa55c55e82d697bde227696a630914
+        // https://libeigen.gitlab.io/docs/classEigen_1_1IterativeSolverBase.html#a7dfa55c55e82d697bde227696a630914
         A_ = A;
 
         if (!A_.isCompressed())
@@ -339,7 +339,7 @@ std::unique_ptr<EigenLinearSolverBase> createIterativeSolver(
         case EigenOption::PreconType::ILUT:
             // TODO for this preconditioner further options can be passed.
             // see
-            // https://eigen.tuxfamily.org/dox/classEigen_1_1IncompleteLUT.html
+            // https://libeigen.gitlab.io/docs/classEigen_1_1IncompleteLUT.html
             return createIterativeSolver<Solver,
                                          Eigen::IncompleteLUT<double>>();
         default:

MathLib/ODE/ODESolverTypes.h

@@ -26,7 +26,7 @@ namespace ODE
  * \tparam N number of rows
  * \tparam M number of columns
  *
- * \see https://eigen.tuxfamily.org/dox/classEigen_1_1Map.html
+ * \see https://libeigen.gitlab.io/docs/classEigen_1_1Map.html
  */
 template <int N, int M>
 using MappedMatrix = Eigen::Map<Eigen::Matrix<double, N, M, Eigen::ColMajor>>;

web/content/docs/devguide/advanced/configuration-options/index.md

@@ -46,7 +46,7 @@ CMake switches to enable / disable parts of OGS.
 - `OGS_CPU_ARCHITECTURE` - Optimizes for the given CPU architecture see [-march](https://gcc.gnu.org/onlinedocs/gcc-4.5.3/gcc/i386-and-x86_002d64-Options.html)-flag. Defaults to `native`. For redistributable binaries set to `generic` on Linux and `core2` on Mac OS. Can be disabled when set to `OFF`.
 - `CMAKE_LIBRARY_SEARCH_PATH` - Additional library installation path, e.g. `/opt/local` or `C:/libs`
 - `OGS_DEPENDENCY_VERSIONS` - Overwrite individual entries in `web/data/versions.json`. Should be quoted and `;`-separated, e.g.: `-DOGS_DEPENDENCY_VERSIONS="minimum_version.petsc=3.16.2;ctest.large_runtime=120"`.
-- `OGS_USE_MKL` - Enables MKL support. Requires MKL to be installed on the system.[^MKL] A CMake or environment variable `MKLROOT` or `MKL_DIR` has to point to the MKL installation directory. To enable 64-bit array indices in MKL add `-DMKL_USE_interface=ilp64` on the first CMake run (with a clean CMake cache) but this seems [not supported by Eigen](https://eigen.tuxfamily.org/dox/TopicUsingIntelMKL.html).
+- `OGS_USE_MKL` - Enables MKL support. Requires MKL to be installed on the system.[^MKL] A CMake or environment variable `MKLROOT` or `MKL_DIR` has to point to the MKL installation directory. To enable 64-bit array indices in MKL add `-DMKL_USE_interface=ilp64` on the first CMake run (with a clean CMake cache) but this seems [not supported by Eigen](https://libeigen.gitlab.io/docs/TopicUsingIntelMKL.html).
 - `OGS_USE_PETSC_MKL_EIGEN_OPENMP` - Also enables OpenMP multithreading when PETSc and MKL is used. This pulls in another OpenMP implementation besides the Intel MKL OpenMP. **Experimental feature!**
 
 [^MKL]: The `mkl_link_tool` (part of the MKL installation) is used for setting up necessary compiler flags. It is a 32-bit executable. On Arch Linux you need to enable the [multilib-repository](https://wiki.archlinux.org/title/official_repositories#Enabling_multilib) and then install the package `lib32-gcc-libs` (otherwise you may get this error when trying to run it: `mkl_link_tool: No such file or directory`) On other Linux distributions you have to install the package `lib32stdc++6` (Ubuntu / Debian) or `libstdc++.i686` (yum-based)! On Windows please also install the *Intel oneAPI Threading Building Blocks* during installation!