Barry,<br><br>sorry if I'm coming off stubborn or something, but I think I'm not following your reasoning.<br><br><div class="gmail_quote"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
NO.<br>
<br>
If you are using LU to construct a preconditioner then you ARE providing the Jacobian explicitly (as a sparse) matrix. Each time the preconditioner is built this sparse matrix is factored.</blockquote><div><br>What do you mean by "providing the jacobian explicity (as a sparse) matrix"? I thought that there was no explicit jacobian matrix, but only a MATMFFD context.<br>
<br>Rafael<br></div></div>