| Author | Message | ||
     Jared Barber (jared_barber) Member Username: jared_barber Post Number: 41 Registered: 01-2007 |
Hello, I have code running and, despite the fact that I use the select switch: vandenberg = off, during the solution process the iteration switches from Lanczos to Vandenberg (and then fails to converge). While I realize that Lanczos might also fail to converge, I would like to turn off Vandenberg to make sure that Lanczos does not converge before proceeding to Vandenberg. If anyone could shed some light on this, that would be great. Thanks, Jared | ||
| Robert G. Nelson (rgnelson) Moderator Username: rgnelson Post Number: 1234 Registered: 06-2003 |
The default behavior for non-symmetric systems is to perform Lanczos iteration. If this method diverges, the solver falls back to the Vandenberg method. The only alternative would be to abort the run. The Vandenberg switch can request exclusive use of the vandenberg iteration method, but cannot prevent its use as a fall-back if the Lanczos method fails. Failure of both methods probably means the system is singular or nearly singular. |