next up previous contents index
Next: 4.1 Setting Up the Up: User's Manual Previous: 3.5 Symmetric Matrices

4 Semi-Structured-Grid System Interface (SStruct)

 

In order to get access to the most efficient and scalable solvers for semi-structured-grid applications (applications with grids that are mostly structured, but with some unstructured features), users should use the SStruct interface described in this chapter. This interface also provides access to solvers in HYPRE that were designed for unstructured-grid applications and sparse linear systems in general. These additional solvers are usually provided via the unstructured-grid interface (FEI) or the linear-algebraic interface (IJ) described in Chapters 5 and 6.

Figure 4.1 gives an example of the type of grid currently supported by the SStruct interface. The grid is composed of three ``parts''. There is a single cell-centered variable across the entire grid, except at the grid cell marked with a square, which has one additional cell-centered variable.

  
Figure 4.1: An example 2D block-structured grid, distributed accross three processes.

There are five basic steps involved in setting up the linear system to be solved:

  1. set up the grid,
  2. set up the stencils,
  3. set up the graph,
  4. set up the matrix,
  5. set up the right-hand-side vector.
To describe each of these steps in more detail, consider solving the 2D Laplacian problem

 

Assume (3.1) is discretized using standard 9-pt finite-volumes on the grid pictured in 4.1, and assume that the problem data is distributed across three processes as depicted. In the figure, each grid part is distributed onto a different process, but this need not be the case; each grid part may also be distributed across several processes. Assume for simplicity and illustration that there is a single coupling between the first and second variables in grid part 0 at index (1,2). In general, this variable may also be coupled to variables at neighboring indices.




next up previous contents index
Next: 4.1 Setting Up the Up: User's Manual Previous: 3.5 Symmetric Matrices

Thomas Treadway
Fri Jul 27 10:01:25 PDT 2001