<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">On 08 Mar 2014, at 23:11, Jose E. Roman <<a href="mailto:jroman@dsic.upv.es">jroman@dsic.upv.es</a>> wrote:<br><div><br><blockquote type="cite"><div style="font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">The nullspace of A^h A is equal to the right singular space of A corresponding to the zero singular value. It should be possible to compute this with SLEPc's SVD. Computing a large number of zeros may be problematic, so I cannot say in advance if the method will succeed. If you can generate a small matrix with these properties, send it to my personal address (not the list) and I will give it a try.<br></div></blockquote></div><br><div>Dear Jose, thank you for the answer. I thought of using the SVD (my solution would correspond to Eq. 4.4).</div><div>SLEPc guide, however, focuses on the case of a null space for A* which is much larger than its range, and </div><div>says that the null space is often not computed at all. Furthermore, of the AA^h and A^hA cases, it says it </div><div>takes the smallest one. In my case, that would be AA^h, and the right singular space of A would be gone at</div><div>the outset. I am glad to hear that the calculation is possible. Most probably. however, I’ll need some hints on </div><div>how to achieve that. Finally, I really appreciate your offer of testing the algorithm; I will try to prepare a test case.</div><div><br></div><div>Cheers,</div><div><br></div><div> Luca</div><div><br></div></body></html>