Specific auxiliaries

• Domain Overlap. The Schwarz methods, being based on overlapping subdomains, need an auxiliary routine for setting the overlap size.

  
  Command: int PCSchwarzSetHaloSize(PC pc,int size)
  		Option:T-pc_halo_size <int>      
  

  For example:

    ierr = PCSchwarzSetHaloSize(the_pc,1);
  

  The overlap size has to be zero or more; for zero it reduces the additive method to block Jacobi and the multiplicative method to generalised block SSOR methods.