Type of additive Schwarz method to use
PC_ASM_BASIC- Symmetric version where residuals from the ghost points are used and computed values in ghost regions are added together. Classical standard additive Schwarz.
PC_ASM_RESTRICT- Residuals from ghost points are used but computed values in ghost region are discarded. Default.
PC_ASM_INTERPOLATE- Residuals from ghost points are not used, computed values in ghost region are added back in.
PC_ASM_NONE- Residuals from ghost points are not used, computed ghost values are discarded. Not very good.