declaration of computation of generalized eigenvalues for symmetric lapack matrices...

git-svn-id: https://svn.dealii.org/trunk@21039 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/lac/include/lac/lapack_full_matrix.h b/deal.II/lac/include/lac/lapack_full_matrix.h
index a6fbbec8912fd31c9eee7fc0036a56c18ba9716d..2180de1e7c1b2699219e99c68705a94263d89eda 100644 (file)
--- a/deal.II/lac/include/lac/lapack_full_matrix.h
+++ b/deal.II/lac/include/lac/lapack_full_matrix.h
@@ -290,6 +290,56 @@ class LAPACKFullMatrix : public TransposeTable<number>
     void compute_eigenvalues (const bool right_eigenvectors = false,
                              const bool left_eigenvectors = false);
 
+                                    /**
+                                     * Compute generalized eigenvalues 
+                                     * and (optionally) eigenvectors of
+                                     * a real generalized symmetric
+                                     * eigenproblem of the form
+                                     * itype = 1: A*x=\lambda*B*x
+                                     * itype = 2: A*B*x=\lambda*x
+                                     * itype = 3: B*A*x=\lambda*x,
+                                     * where A is this matrix.
+                                     * A and B are assumed to be symmetric,
+                                     * and B has to be positive definite.
+                                     * After this routine has
+                                     * been called, eigenvalues can
+                                     * be retrieved using the
+                                     * eigenvalue() function. The
+                                     * matrix itself will be
+                                     * LAPACKSupport::unusable after
+                                     * this operation. The number of
+                                     * computed eigenvectors is equal
+                                     * to eigenvectors.size()
+                                     *
+                                     * Note that the function does
+                                     * not return the computed
+                                     * eigenvalues right away since
+                                     * that involves copying data
+                                     * around between the output
+                                     * arrays of the LAPACK functions
+                                     * and any return array. This is
+                                     * often unnecessary since one
+                                     * may not be interested in all
+                                     * eigenvalues at once, but for
+                                     * example only the extreme
+                                     * ones. In that case, it is
+                                     * cheaper to just have this
+                                     * function compute the
+                                     * eigenvalues and have a
+                                     * separate function that returns
+                                     * whatever eigenvalue is
+                                     * requested.
+                                     * 
+                                     * @note Calls the LAPACK
+                                     * function Xsygv. For this to
+                                     * work, ./configure has to
+                                     * be told to use LAPACK.
+                                     */
+    void compute_generalized_eigenvalues_symmetric (
+                              LAPACKFullMatrix<number> & B,
+                              std::vector<Vector<number> > & eigenvectors,
+                             const int itype = 1);
+
                                     /**
                                      * Retrieve eigenvalue after
                                      * compute_eigenvalues() was