How can I tell if the ANSYS sparse solver has used the pivoting option?
Pivoting is a technique in which the solution of singular equations is postponed until the other
equations have been solved, at which time it is less likely to be singular. We automatically turn
on pivoting for certain problems - generally the U/P formulation elements and 17x elements.
If bcsopt,,,,,,-5 is added there will be a message with the solver output that tells when the pivoting
option is in use.
The effect on performance ranges from next to nothing to a LOT, depending on whether pivoting
actually happens. Turning it on just means we test for small diags and pivot when the
test threshold is reached. Pivoting generally increases memory and op count but it is only significant
when a lot of pivoting happens. I avoid it if possible and in some cases it is good to override our default of
turning it on by using eqsolve,sparse,-1