Add Spectra.

thirdparty/include/Spectra/Util/CompInfo.h

@@ -0,0 +1,36 @@
+// Copyright (C) 2016-2022 Yixuan Qiu <yixuan.qiu@cos.name>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#ifndef SPECTRA_COMP_INFO_H
+#define SPECTRA_COMP_INFO_H
+
+namespace Spectra {
+
+///
+/// \ingroup Enumerations
+///
+/// The enumeration to report the status of computation.
+///
+enum class CompInfo
+{
+    Successful,  ///< Computation was successful.
+
+    NotComputed,  ///< Used in eigen solvers, indicating that computation
+                  ///< has not been conducted. Users should call
+                  ///< the `compute()` member function of solvers.
+
+    NotConverging,  ///< Used in eigen solvers, indicating that some eigenvalues
+                    ///< did not converge. The `compute()`
+                    ///< function returns the number of converged eigenvalues.
+
+    NumericalIssue  ///< Used in various matrix factorization classes, for example in
+                    ///< Cholesky decomposition it indicates that the
+                    ///< matrix is not positive definite.
+};
+
+}  // namespace Spectra
+
+#endif  // SPECTRA_COMP_INFO_H