[MaL/LA/PETSc] LinearSolverOptionsParser templ. spezialisation.

MathLib/LinAlg/PETSc/LinearSolverOptionsParser.h

+/**
+ * \file
+ * \copyright
+ * Copyright (c) 2012-2021, OpenGeoSys Community (http://www.opengeosys.org)
+ *            Distributed under a Modified BSD License.
+ *              See accompanying file LICENSE.txt or
+ *              http://www.opengeosys.org/project/license
+ *
+ */
+
+#pragma once
+
+#include "BaseLib/ConfigTree.h"
+#include "MathLib/LinAlg/LinearSolverOptions.h"
+#include "MathLib/LinAlg/LinearSolverOptionsParser.h"
+#include "MathLib/LinAlg/PETSc/PETScLinearSolver.h"
+
+namespace MathLib
+{
+template <>
+struct LinearSolverOptionsParser<PETScLinearSolver> final
+{
+    /// The method parses the linear solver options for PETSc.
+    /// @param solver_prefix the prefix for the linear solver to distinguish
+    /// different linear solvers for instance in the staggered schema
+    /// @param config the part of the property tree (usually created from the
+    /// linear solver section in the project file)
+    /// @return the first item of the returned tuple is the solver prefix as
+    /// string, the second item are all the options passed as string to PETSc
+    /// options database
+    std::tuple<std::string, std::string> parseNameAndOptions(
+        std::string solver_prefix,
+        BaseLib::ConfigTree const* const config) const
+    {
+        // Insert options into petsc database. Default options are given in the
+        // string below.
+        std::string petsc_options =
+            "-ksp_type cg -pc_type bjacobi -ksp_rtol 1e-16 -ksp_max_it 10000";
+
+        if (config)
+        {
+            ignoreOtherLinearSolvers(*config, "petsc");
+
+            //! \ogs_file_param{prj__linear_solvers__linear_solver__petsc}
+            if (auto const subtree = config->getConfigSubtreeOptional("petsc"))
+            {
+                if (auto const parameters =
+                        //! \ogs_file_param{prj__linear_solvers__linear_solver__petsc__parameters}
+                    subtree->getConfigParameterOptional<std::string>(
+                        "parameters"))
+                {
+                    petsc_options = *parameters;
+                }
+
+                if (auto const pre =
+                        //! \ogs_file_param{prj__linear_solvers__linear_solver__petsc__prefix}
+                    subtree->getConfigParameterOptional<std::string>("prefix"))
+                {
+                    if (!pre->empty())
+                        solver_prefix = *pre + "_";
+                }
+            }
+        }
+        return {solver_prefix, petsc_options};
+    }
+};
+
+}  // namespace MathLib