1  int n = 10000;
2  VectorXd x(n), b(n);
3  SparseMatrix<double> A(n,n);
4  /* ... fill A and b ... */
5  BiCGSTAB<SparseMatrix<double> > solver;
6  solver.compute(A);
7  x = solver.solve(b);
8  std::cout << "#iterations:     " << solver.iterations() << std::endl;
9  std::cout << "estimated error: " << solver.error()      << std::endl;
10  /* ... update b ... */
11  x = solver.solve(b); // solve again