Eigen/OrderingMethods

// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// 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 http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_ORDERINGMETHODS_MODULE_H
#define EIGEN_ORDERINGMETHODS_MODULE_H

#include "SparseCore"

#include "src/Core/util/DisableStupidWarnings.h"

/**
 * \defgroup OrderingMethods_Module OrderingMethods module
 *
 * This module is currently for internal use only
 *
 * It defines various built-in and external ordering methods for sparse matrices.
 * They are typically used to reduce the number of elements during
 * the sparse matrix decomposition (LLT, LU, QR).
 * Precisely, in a preprocessing step, a permutation matrix P is computed using
 * those ordering methods and applied to the columns of the matrix.
 * Using for instance the sparse Cholesky decomposition, it is expected that
 * the nonzeros elements in LLT(A*P) will be much smaller than that in LLT(A).
 *
 *
 * Usage :
 * \code
 * #include <Eigen/OrderingMethods>
 * \endcode
 *
 * A simple usage is as a template parameter in the sparse decomposition classes :
 *
 * \code
 * SparseLU<MatrixType, COLAMDOrdering<int> > solver;
 * \endcode
 *
 * \code
 * SparseQR<MatrixType, COLAMDOrdering<int> > solver;
 * \endcode
 *
 * It is possible as well to call directly a particular ordering method for your own purpose,
 * \code
 * AMDOrdering<int> ordering;
 * PermutationMatrix<Dynamic, Dynamic, int> perm;
 * SparseMatrix<double> A;
 * //Fill the matrix ...
 *
 * ordering(A, perm); // Call AMD
 * \endcode
 *
 * \note Some of these methods (like AMD or METIS), need the sparsity pattern
 * of the input matrix to be symmetric. When the matrix is structurally unsymmetric,
 * Eigen computes internally the pattern of \f$A^T*A\f$ before calling the method.
 * If your matrix is already symmetric (at least in structure), you can avoid that
 * by calling the method with a SelfAdjointView type.
 *
 * \code
 *  // Call the ordering on the pattern of the lower triangular matrix A
 * ordering(A.selfadjointView<Lower>(), perm);
 * \endcode
 */

// IWYU pragma: begin_exports
#include "src/OrderingMethods/Amd.h"
#include "src/OrderingMethods/Ordering.h"
// IWYU pragma: end_exports

#include "src/Core/util/ReenableStupidWarnings.h"

#endif  // EIGEN_ORDERINGMETHODS_MODULE_H