It turns out that 'hg rollback' during an 'hg rebase' does not do what I thought it did. I think everything is cleaned up with this push, but if you made FS changes in the past month, please check that it is doing what you want with prefixes, etc. Now, nested fieldsplits from the command line work, ala -ksp_type fgmres -pc_type fieldsplit -pc_fieldsplit_type additive -pc_fieldsplit_0_fields 0,1 -fieldsplit_0_pc_type fieldsplit -fieldsplit_0_pc_fieldsplit_type schur -fieldsplit_0_pc_fieldsplitschur_factorization_type full -fieldsplit_0_fieldsplit_velocity_ksp_type preonly -fieldsplit_0_fieldsplit_velocity_pc_type lu -fieldsplit_0_fieldsplit_pressure_ksp_rtol 1e-10 -fieldsplit_0_fieldsplit_pressure_pc_type jacobi -pc_fieldsplit_1_fields 2 -fieldsplit_temperature_ksp_type preonly -fieldsplit_temperature_pc_type lu A split with only one field gets the field name, and otherwise a split number. Matt -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener