Sets the lower and upper bounds for the solution vector. xl <= x <= xu. This allows solving (differential) variable inequalities.
snes - the
xl - lower bound.
xu - upper bound.
If this routine is not called then the lower and upper bounds are set to
PETSC_INFINITY respectively during
For particular components that have no bounds you can use
SNESVISetVariableBounds() can be used to provide a function that computes the bounds. This should be used if you are using, for example, grid
sequencing and need bounds set for a variety of vectors