I am not sure if I understand you correctly. During initialization, several matrices are formed by kronecker products, and the resulting matrices have the size of the number of unknowns; i.e. if n is the number of unknowns then the matrices are n x n, although they typically have only a*n nonzero elements, with a around 10-20. After initialization a time loop starts in which these matrices are used for matrix-vector products (e.g. to calculate a first or second derivative) and things like CG or Multigrid are used to solve a number of matrix-vector equations (e.g. a Poisson equation for the pressure). This is repeated each time step.
----- Original Message ----- From: "Jed Brown" <[email protected]> To: "PETSc users list" <petsc-users at mcs.anl.gov> Sent: Thursday, November 4, 2010 4:03:15 PM Subject: Re: [petsc-users] kronecker products On Thu, Nov 4, 2010 at 09:58, Benjamin Sanderse <B.Sanderse at cwi.nl> wrote: > Some matrices are just used to compute matrix-vector products, and some > have to be solved for. That's basically it. > The matrices are really very sparse; on the order of 10-20 diagonals > (typically independent of problem size). > As far as I know, reordering is hardly necessary, because I am using a > structured grid. > What are the relative sizes of each piece? How are you producing these matrices? How do you want the vector distributed? Jed
