## VecScatter

- <CONCEPT>using vector scatter operations;</CONCEPT> An Unstructured Grid Example.
  This example demonstrates how to solve a nonlinear system in parallel
  with SNES for an unstructured mesh. The mesh and partitioning information
  is read in an application defined ordering,which is later transformed
  into another convenient ordering (called the local ordering). The local
  ordering, apart from being efficient on cpu cycles and memory, allows
  the use of the SPMD model of parallel programming. After partitioning
  is done, scatters are created between local (sequential)and global
  (distributed) vectors. Finally, we set up the nonlinear solver context
  in the usual way as a structured grid (see
  petsc/src/snes/examples/tutorials/ex5.c).