Klaus Burkart <k_burk...@yahoo.com> writes: > Hi, > How can I preallocate space for matrices (some symmetric, others > asymmetric) if I have the global number of nonzeros (NNZ) but not the > number of nonzeros per row?
Unfortunately, this is not enough for efficient assembly. It is more efficient to over-estimate. > I could compute the NNZ for the upper or lower part separately if this > would be useful for symmetric matrices. > > I create the matrix this way: > MatCreate(PETSC_COMM_WORLD, &M); > MatSetSizes(M, PETSC_DECIDE, PETSC_DECIDE, N, N); > MatSetFromOptions(M); > Klaus