Restriction to a Subdomain

Assume that

• x is a variable Variable< ... , sx , sy , sz >

• subgrid is a variable of type Variable<bool , sx , sy , sz > , and

• Expr is an expression. Than, the statement

   x = Expr | subgrid;

is evaluated at every grid point, where subgrid has the value true.

The values of variable subgrid can be set by any expression. However, there is a special construction to set the values of subgrid. Let

       bool  (*Marker_formula)(double x, double y, double z);

be a formula which marks a subgrid of the discretization grid. This means that Marker_formula returns the value true if and only if the point (x,y,z) is contained in the subgrid. Then, the construction

subgrid = Marker_formula;

sets the value true at all grid points of the marked subgrid.

Last modified: Fri Jun 1 11:41:25 PDT 2001