<div class="gmail_quote">On Mon, Apr 23, 2012 at 08:41, Matthew Knepley <span dir="ltr"><<a href="mailto:knepley@gmail.com">knepley@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>-snes_mf uses FD to approximate the ACTION of the operator. The above</div><div>quotes are talking about using FD to approximate the operator itself.</div></blockquote></div><br><div>I.e., to assemble as a sparse matrix, so that it can be used as input to a preconditioning method.</div>