On 08 Mar 2014, at 23:11, Jose E. Roman <[email protected]> wrote:
> 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.
Dear Jose, thank you for the answer. I thought of using the SVD (my solution
would correspond to Eq. 4.4).
SLEPc guide, however, focuses on the case of a null space for A* which is much
larger than its range, and
says that the null space is often not computed at all. Furthermore, of the AA^h
and A^hA cases, it says it
takes the smallest one. In my case, that would be AA^h, and the right singular
space of A would be gone at
the outset. I am glad to hear that the calculation is possible. Most probably.
however, I’ll need some hints on
how to achieve that. Finally, I really appreciate your offer of testing the
algorithm; I will try to prepare a test case.
Cheers,
Luca
