The short answer is that preallocation looks exactly like an assembly, but individual values are not calculated, just sizes. You can look at the routines I have for this for the Mesh class in preallocateOperator() in src/dm/mesh/mesh.c.
Matt On Nov 1, 2007 4:17 PM, Berend van Wachem <berend at chalmers.se> wrote: > Hi Barry, > > > > Perhaps you could describe how your matrix entries are generated and > > we can suggest a > > preallocation scheme? > > Are there examples of preallocation schemes for PETSc? For instance, if > I would like to solve Poisson equation on an irregular grid (9 point > stencil in 2d and 27 in 3d) on n processors? > > Thanks, > Berend. > > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener
