/*   ARPACK++ v1.0 8/1/1997   c++ interface to ARPACK code.   MODULE ASymGShf.cc.   Example program that illustrates how to solve a real symmetric   generalized eigenvalue problem in Cayley mode using the AREig   function.   1) Problem description:      In this example we try to solve A*x = B*x*lambda in Cayley mode,      where A and B are obtained from the finite element discretization      of the 1-dimensional discrete Laplacian                                  d^2u / dx^2      on the interval [0,1] with zero Dirichlet boundary conditions      using piecewise linear elements.   2) Data structure used to represent matrices A and B:      {nnzA, irowA, pcolA, valA}: upper triangular part of matrix A                                  stored in CSC format.      {nnzB, irowB, pcolB, valB}: upper triangular part of matrix B                                  stored in CSC format.   3) Library called by this example:      The SuperLU package is called by AREig to solve some linear      systems involving (A-sigma*B).   4) Included header files:      File             Contents      -----------      -------------------------------------------      lsmatrxc.h       SymmetricMatrixC, a function that generates                       matrix A in CSC format.      lsmatrxd.h       SymmetricMatrixD, a function that generates                       matrix B in CSC format.      areig.h          The AREig function definition.      asymsol.h        The Solution function.   5) ARPACK Authors:      Richard Lehoucq      Kristyn Maschhoff      Danny Sorensen      Chao Yang      Dept. of Computational & Applied Mathematics      Rice University      Houston, Texas*/#include "lsmatrxc.h"#include "lsmatrxd.h"#include "areig.h"#include "asymsol.h"main(){  // Defining variables;  int    n;              // Dimension of the problem.  int    nconv;          // Number of "converged" eigenvalues.  int    nnzA,   nnzB;   // Number of nonzero elements in A and B.  int    *irowA, *irowB; // pointer to an array that stores the row                         // indices of the nonzeros in A and B.  int    *pcolA, *pcolB; // pointer to an array of pointers to the                         // beginning of each column of A (B) in valA (valB).  double *valA,  *valB;  // pointer to an array that stores the nonzero                         // elements of A and B.  double EigVal[101];    // Eigenvalues.  double EigVec[1001];   // Eigenvectors stored sequentially.  char   uplo;           // Variable that indicates whether the upper                         // (uplo='U') ot the lower (uplo='L') part of                         // A and B will be supplied to AREig.  // Creating matrices A and B.  n = 100;  uplo = 'U';  SymmetricMatrixC(n, nnzA, valA, irowA, pcolA, uplo);  SymmetricMatrixD(n, nnzB, valB, irowB, pcolB, uplo);  // Finding the four eigenvalues of A nearest to 150.0 and the  // related eigenvectors.  nconv = AREig(EigVal, EigVec, n, nnzA, valA, irowA, pcolA,                nnzB, valB, irowB, pcolB, uplo, 'C', 150.0, 4);  // Printing solution.  Solution(nconv, n, nnzA, valA, irowA, pcolA, nnzB,           valB, irowB, pcolB, uplo, EigVal, EigVec);} // main.