On 5/9/06, <b class="gmail_sendername">Yaron Kretchmer</b> <<a href="mailto:yaronkretchmer@gmail.com">yaronkretchmer@gmail.com</a>> wrote:<div><span class="gmail_quote"></span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div style="direction: ltr;"><div>Hi all</div>
<div>I have a matrix representing electrical currents (KCL). In my
design, there are some elements which are totally isolated from the
rest of the circuit, which means that they form the matrix's nullspace.</div>
<div> </div>
<div>My questions are:</div>
<div>*) Can I use Petsc to derive the nodes which compose the nullspace</div></div></blockquote><div><br>
We do not have QR type algorithms in PETSc, but you could use LAPACK or<br>
PLAPACK for dense matrices.<br>
</div><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div style="direction: ltr;"><div>*) Can I then remove them from the KSP? If so, how?
</div></div></blockquote><div><br>
You can use the MatNullSpace architecture to remove these components from a solve.<br>
<br>
Matt <br>
</div><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div style="direction: ltr;"><div>Thanks much</div></div><div style="direction: ltr;">
<span class="sg">
<div>Yaron</div>
<div> </div>
</span></div></blockquote></div><br><br clear="all"><br>-- <br>"Failure has a thousand explanations. Success doesn't need one" -- Sir Alec Guiness