F02FKF Example Program Data
 20      : nx, matrix order n = nx*nx
 8       : nev, number of eigenvalues requested
 20      : ncv, size of subspace
 1.0     : sigma, shift (want eigenvalues close to sigma)
 0       : print level
 500     : maximum number of itrerations
 1       : mode (0 = regular, 1 = shifted inverse)
 0       : imon (0 = no monitoring, 1 = monitoring on)