Re: [petsc-users] fieldsplit: Unhandled case, must have at least two fields, not 1!

[Mark Adams]

>
>
>
>       if (i == 0) {
>         for (f = 0; f < numFields; ++f) {
>           ierr = PCFieldSplitSetIS(pc, fieldNames[f],
> fields[f]);CHKERRQ(ierr);
>           ierr = PetscFree(fieldNames[f]);CHKERRQ(ierr);
>           ierr = ISDestroy(&fields[f]);CHKERRQ(ierr);
>         }
>
> numFields should be 2.  Compare to src/snes/examples/tutorials/ex28.c
> (adapting runex28_3),
>

The matrix/solver just has one field. The error comes from giving it field
split parameters by mistake.