Update Spectra to v1.0.1 to fix C++20 compatibility issues on GCC/Clang

gtsam/3rdparty/Spectra/Spectra/DavidsonSymEigsSolver.h

@@ -0,0 +1,93 @@
+// Copyright (C) 2020 Netherlands eScience Center <[email protected]>
+//
+// 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_DAVIDSON_SYM_EIGS_SOLVER_H
+#define SPECTRA_DAVIDSON_SYM_EIGS_SOLVER_H
+
+#include <Eigen/Core>
+
+#include "JDSymEigsBase.h"
+#include "Util/SelectionRule.h"
+
+namespace Spectra {
+
+///
+/// \ingroup EigenSolver
+///
+/// This class implement the DPR correction for the Davidson algorithms.
+/// The algorithms in the Davidson family only differ in how the correction
+/// vectors are computed and optionally in the initial orthogonal basis set.
+///
+/// the DPR correction compute the new correction vector using the following expression:
+/// \f[ correction = -(\boldsymbol{D} - \rho \boldsymbol{I})^{-1} \boldsymbol{r} \f]
+/// where
+/// \f$D\f$ is the diagonal of the target matrix, \f$\rho\f$ the Ritz eigenvalue,
+/// \f$I\f$ the identity matrix and \f$r\f$ the residue vector.
+///
+template <typename OpType>
+class DavidsonSymEigsSolver : public JDSymEigsBase<DavidsonSymEigsSolver<OpType>, OpType>
+{
+private:
+    using Index = Eigen::Index;
+    using Scalar = typename OpType::Scalar;
+    using Matrix = Eigen::Matrix<Scalar, Eigen::Dynamic, Eigen::Dynamic>;
+    using Vector = Eigen::Matrix<Scalar, Eigen::Dynamic, 1>;
+
+    Vector m_diagonal;
+
+public:
+    DavidsonSymEigsSolver(OpType& op, Index nev, Index nvec_init, Index nvec_max) :
+        JDSymEigsBase<DavidsonSymEigsSolver<OpType>, OpType>(op, nev, nvec_init, nvec_max)
+    {
+        m_diagonal.resize(this->m_matrix_operator.rows());
+        for (Index i = 0; i < op.rows(); i++)
+        {
+            m_diagonal(i) = op(i, i);
+        }
+    }
+
+    DavidsonSymEigsSolver(OpType& op, Index nev) :
+        DavidsonSymEigsSolver(op, nev, 2 * nev, 10 * nev) {}
+
+    /// Create initial search space based on the diagonal
+    /// and the spectrum'target (highest or lowest)
+    ///
+    /// \param selection Spectrum section to target (e.g. lowest, etc.)
+    /// \return Matrix with the initial orthonormal basis
+    Matrix setup_initial_search_space(SortRule selection) const
+    {
+        std::vector<Eigen::Index> indices_sorted = argsort(selection, m_diagonal);
+
+        Matrix initial_basis = Matrix::Zero(this->m_matrix_operator.rows(), this->m_initial_search_space_size);
+
+        for (Index k = 0; k < this->m_initial_search_space_size; k++)
+        {
+            Index row = indices_sorted[k];
+            initial_basis(row, k) = 1.0;
+        }
+        return initial_basis;
+    }
+
+    /// Compute the corrections using the DPR method.
+    ///
+    /// \return New correction vectors.
+    Matrix calculate_correction_vector() const
+    {
+        const Matrix& residues = this->m_ritz_pairs.residues();
+        const Vector& eigvals = this->m_ritz_pairs.ritz_values();
+        Matrix correction = Matrix::Zero(this->m_matrix_operator.rows(), this->m_correction_size);
+        for (Index k = 0; k < this->m_correction_size; k++)
+        {
+            Vector tmp = eigvals(k) - m_diagonal.array();
+            correction.col(k) = residues.col(k).array() / tmp.array();
+        }
+        return correction;
+    }
+};
+
+}  // namespace Spectra
+
+#endif  // SPECTRA_DAVIDSON_SYM_EIGS_SOLVER_H