PCFIELDSPLIT

Preconditioner created by combining separate preconditioners for individual fields or groups of fields

To set options on the solvers for each block append -sub_ to all the PC options database keys. For example, -sub_pc_type ilu -sub_pc_factor_levels 1

To set the options on the solvers separate for each block call PCFieldSplitGetSubKSP() and set the options directly on the resulting KSP object

	-pc_splitfield_%d_fields <a,b,..>	- indicates the fields to be used in the %d'th split
	-pc_splitfield_default	- automatically add any fields to additional splits that have not been supplied explicitly by -pc_splitfield_%d_fields
	-pc_splitfield_block_size <bs>	- size of block that defines fields (i.e. there are bs fields)
	-pc_splitfield_type <additive,multiplicative>	-