  dnaupd - Interface for the Implicitly Restarted Arnoldi Iteration, to compute approximations to a few eigenpairs of a real linear operator
  dsaupd - Interface for the Implicitly Restarted Arnoldi Iteration, to compute approximations to a few eigenpairs of a real and symmetric linear operator
  gmres - generalized minimum residual method with restarts
  pcg - precondioned conjugate gradient
  qmr - quasi minimal resiqual method with preconditioning