[eigen-solver.internal.base] add constructor

dune/xt/la/eigen-solver/internal/base.hh

@@ -40,7 +40,7 @@ class EigenSolverOptions;
 namespace internal {
 
 
-static void ensure_eigen_solver_type(const std::string& type, const std::vector<std::string>& available_types)
+static inline void ensure_eigen_solver_type(const std::string& type, const std::vector<std::string>& available_types)
 {
   bool contained = false;
   for (const auto& tp : available_types)
@@ -52,7 +52,7 @@ static void ensure_eigen_solver_type(const std::string& type, const std::vector<
 } // ... ensure_type(...)
 
 
-static Common::Configuration default_eigen_solver_options()
+static inline Common::Configuration default_eigen_solver_options()
 {
   Common::Configuration opts;
   opts["compute_eigenvalues"] = "true";
@@ -106,6 +106,15 @@ public:
     pre_checks();
   }
 
+  EigenSolverBase(const MatrixType& matrix, Common::Configuration* opts)
+    : matrix_(matrix)
+    , options_(opts)
+    , computed_(false)
+    , disable_checks_(options_->get<bool>("disable_checks", false))
+  {
+    pre_checks();
+  }
+
   EigenSolverBase(const ThisType& other) = default;
 
   EigenSolverBase(ThisType&& source) = default;